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Glass Fiber-Reinforced Polymer (GFRP) and Steel Strengthening of Unreinforced Brick Masonry Piers


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GLASS FIBER-REINFORCED POLYMER (GFRP) AND S TEEL STRENGTHENING OF UNREINFORCED BRICK MASONRY PIERS By WILLIAM P. SWANSON A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ENGINEERING UNIVERSITY OF FLORIDA 2004

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Copyright 2004 by William P. Swanson

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ACKNOWLEDGMENTS Acknowledgements go to the National Science Foundation and the Marketing Developing Alliance for the Composites Industry for their financial support of this research. I thank Dr. H. R. Hamilton for providing me the opportunity to perform this work and helping me along the way. Dr. Ronald A. Cook and Dr. Gary Consolazio deserve thanks as members of my committee. iii

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iv TABLE OF CONTENTS page ACKNOWLEDGMENTS.................................................................................................iii LIST OF TABLES.............................................................................................................vi LIST OF FIGURES.........................................................................................................viii ABSTRACT.....................................................................................................................xi ii CHAPTER 1 INTRODUCTION AND OBJECTIVES......................................................................1 Introduction................................................................................................................... 1 Research Objectives......................................................................................................4 2 EXPERIMENTAL PROGRAM...................................................................................6 Test Specimens.............................................................................................................6 Material properties........................................................................................................7 GFRP Composite Reinforcement.................................................................................8 Steel Reinforcement....................................................................................................11 Test Setup...................................................................................................................13 Test Procedures...................................................................................................14 Instrumentation....................................................................................................15 3 EXPERIMENTAL RESULTS...................................................................................19 Specimen Behavior.....................................................................................................19 Load-Displacement Envelopes...................................................................................29 Ductility Of Masonry Systems...................................................................................30 Computing Predicted Capacities.................................................................................33 4 CONCLUSIONS........................................................................................................36 APPENDIX A LITERATURE REVIEW...........................................................................................37

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v B SPECIMEN CONSTRUCTION.................................................................................50 C EXPERIMENTAL PROGRAM.................................................................................58 D SPECIMEN DETAILS AND RESULTS...................................................................75 LIST OF REFERENCES.................................................................................................122 BIOGRAPHICAL SKETCH...........................................................................................123

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vi LIST OF TABLES Table page 1 Material Properties.....................................................................................................8 2 GFRP configuration Tests 1h 5..............................................................................10 3 Instrument type and function....................................................................................16 4 Results of cyclic testing............................................................................................22 5 m factors per FEMA 273 for specimens with steel..................................................32 6 Curvature ductility factors specimens reinforced only with GFRP.......................32 7 Measured and Calculated Lateral Capacities..........................................................35 8 Instrumentation description......................................................................................65 9 Individual bricks Compressive strength.................................................................72 10 Brick prisms Compressive strength.......................................................................72 11 Steel rebar Tensile strength....................................................................................73 12 Glass rebar Tensile strength...................................................................................73 13 FRP bond tests Wire brushed wall.........................................................................73 14 FRP bond tests Sand blasted wall..........................................................................73 15 FRP description test 1h.........................................................................................76 16 Crack occurrence......................................................................................................77 17 FRP description Test 1i.........................................................................................81 18 Crack occurrence Test 1i.......................................................................................82 19 FRP description test 2...........................................................................................86 20 Crack occurrence Test 2........................................................................................87

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vii 21 FRP description test 4...........................................................................................91 22 Crack occurrence Test 4........................................................................................91 23 FRP description test 5...........................................................................................96 24 Crack occurrence test 5.........................................................................................96 25 FRP description Test 6........................................................................................101 26 Crack occurrence test 6.......................................................................................101 27 FRP description Test 7.........................................................................................105 28 Crack occurrence Test 7......................................................................................106 29 FRP descripton Test 8.........................................................................................110 30 Crack occurrence Test 8......................................................................................111 31 FRP description Test 9........................................................................................117 32 Crack occurrence Test 9......................................................................................118

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viii LIST OF FIGURES Figure page 1 Pier strengthened with FRP........................................................................................4 2 Model for specimens..................................................................................................4 3 Configuration of specimens.......................................................................................7 4 General GFRP laminate placement............................................................................9 5 Location and orientation of steel reinforcement......................................................12 6 Test setup view from the North................................................................................13 7 String and linear pot location for all walls...............................................................15 8 GFRP strain gauge locations for Specimen 1h, 1i, 5, 6...........................................16 9 Steel strain gauge locations for Specimen 2.............................................................17 10 GFRP and steel strain gauge locations for Specimen 4...........................................17 11 GFRP and steel strain gauge locations for Specimen 7...........................................17 12 Glass rebar strain gauge locations for Specimen 8..................................................17 13 GFRP and steel strain gauge locations for Specimen 9...........................................18 14 Cyclic behavior of Test 1h GFRP laminate only...................................................19 15 Cyclic behavior of Test 1i Sp ecimen 1h repaired with spray-up GFRP...............20 16 Cyclic behavior of Test 2 GFRP laminate, 2-#3 reinforcing steel bars...............20 17 Cyclic behavior of Test 4 GFRP laminate, 4-#3 reinforcing steel bars................20 18 Cyclic behavior of Test 5 GFRP laminate only....................................................20 19 Cyclic behavior of Test 6 GFRP Pre-impregnated only.......................................21 20 Cyclic behavior of Test 7 GFRP laminate, 2-#3 reinforcing steel bars................21

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ix 21 Cyclic behavior of Test 8 GFRP #3 reinforcement...............................................21 22 Cyclic behavior of Test 9 GFRP laminate, 2-#3 reinforcing steel bars.................21 23 Crack pattern for test 2 (North face)........................................................................24 24 A Test 2, east edge of pier. B T est 4, south side east edge of pier......................25 25 In-plane movement base of pier.............................................................................26 26 Crack pattern for test 8.............................................................................................27 27 Strain measured in GFRP bar A at north end of pier...............................................28 28 Crack pattern for test 9.............................................................................................28 29 Backbone curves speci mens with no steel.............................................................29 30 Backbone curves specimens with steel..................................................................29 31 Force-displacement curve for Unreinforced Masonry strengthened with fully bonded GFRP composite and inadequately bonded GFRP composite....................30 32 Method for obtaining values to calculate curvature ductility...................................33 33 Schematic for predicting specimen capacity............................................................35 34 Illustration of specimen model................................................................................50 35 Specimens II VIII Tests 1h, 1i, 2, 4, 5, 6, 7, 8...................................................51 36 Specimen I Test 9..................................................................................................51 37 A Base lintel, B First course of brick being laid.................................................52 38 A Brick laying and B grouting............................................................................52 39 A and B Laying pier bricks....................................................................................53 40 Laying header course...............................................................................................53 41 Completed specimen (no top lintel).........................................................................53 42 Applying FRP to a concrete block wall...................................................................56 43 Epoxy injection system............................................................................................56 44 A and B Injecting epoxy into rebar hole................................................................57 45 Typical steel rebar configuration..............................................................................57

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x 46 Test stand North elevation.....................................................................................59 47 Test stand East elevation........................................................................................60 48 Specimen installed in test stand...............................................................................62 49 Reaction frame.........................................................................................................62 50 Lateral movement prevention struts.........................................................................63 51 Wall end of a lateral movement prevention strut.....................................................63 52 One of two 'gravity' load springs..............................................................................64 53 Specimen handling fixture.......................................................................................64 54 Instrumentat locations (stri ng and linear pots) all walls........................................65 55 FRP strain gauge location Tests 1h, 1i, 5, 6...........................................................67 56 FRP and steel strain gauge locations Test 4...........................................................67 57 FRP and steel strain gauge locations Test 7...........................................................67 58 Glass rebar strain gauge locations Test 8...............................................................68 59 FRP and steel strain gauge locations Test 9...........................................................68 60 Steel strain gauge location Test 2..........................................................................68 61 Steel strain gauge installation...................................................................................69 62 LabVIEW program main screen..............................................................................70 63 MTS Signal Generation program screen..................................................................70 64 FRP layup North side............................................................................................76 65 FRP layup South side............................................................................................76 66 Crack pattern at failure.............................................................................................77 67 A North side. B South side.................................................................................77 68 Progression of glass debonding (black lines)...........................................................78 69 Data reduction plots.................................................................................................79 70 A Spray on/ FRP layup North side. B FRP layup South side............................81

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xi 71 Crack pattern at failure.............................................................................................82 72 Overall view North side........................................................................................82 73 Tear in FRP..............................................................................................................83 74 Data reduction plots.................................................................................................84 75 A FRP layup North side. B FRP layup South side.............................................86 76 Crack pattern at failure A North side, B South side...........................................87 77 A Overall view North side. B view South side...............................................88 78 A East edge of pier. B South side crack pattern.................................................88 79 FRP pulloff North side..........................................................................................88 80 Data reduction plots test 2.....................................................................................89 81 FRP layup A North side, B South side..............................................................91 82 Crack pattern at failure A North side, B South side...........................................92 83 A North side, B North side, east edge of pier....................................................92 84 A South side, east edge of pier, B South side lower center of pier....................92 85 Data reduction plots Test 4....................................................................................94 86 FRP layup North side (No FRP on south side).....................................................96 87 Crack pattern at failure North side (Glass rupture is vertical strip A, east)..........97 88 Crack pattern at failure South side........................................................................97 89 A overall view, B West edge of pier..................................................................98 90 A Glass break in vertical strip A east edge, B Delamination pattern..............98 91 Data reduction plots Test 5....................................................................................99 92 FRP layup North side (No FRP on south side)...................................................101 93 Crack pattern at failure A North side, B South side ( glass rupture is A straps)...................................................................................102 94 A Overall view Nort h side, B South side.........................................................102 95 North side after test................................................................................................102

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xii 96 Data reduction plots test 6...................................................................................103 97 FRP layup Test 7.................................................................................................105 98 Crack pattern at failure A North side, B South side.........................................106 99 A Overall view, B FRP dela mination, east edge of pier..................................107 100 A North side, west edge of pier, B South side, west edge of pier....................107 101 A delamination North side, B south side..........................................................107 102 Data reduction plots test 7...................................................................................108 103 Glass rebar installation/location test 8................................................................110 104 A Pier section glass rebar location, B typical single bar inch groove, C Vertical bars inch groove. Horizontal bar crosses outside.............................111 105 Crack pattern at failure A North side, B South side.........................................112 106 Overall view North side......................................................................................113 107 North side of base A east edge, B west edge...................................................113 108 South side of base A west edge, B east edge......................................................113 109 Data reduction plots Test 8..................................................................................115 110 FRP layup North side Test 9...............................................................................117 111 Crack pattern at failure A North side, B South side............................................118 112 Overall view North side......................................................................................119 113 A South side, B North side...............................................................................119 114 Data reduction plots Test 9..................................................................................121

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xiii Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Engineering GLASS FIBER-REINFORCED POLYMER (GFRP) AND STEEL STRENGTHENING OF UNREINFORCED BRICK MASONRY PIERS By William P. Swanson May 2004 Chair: H. R. Hamilton Major Department: Civil and Coastal Engineering This thesis presents research on the strengthening of unreinforced masonry (URM) piers with glass fiber-reinforced polymers (GFRP) in conjunction with ductile reinforcement. Eight brick masonry pier specimens were strengthened with a combination of GFRP composite strips and reinforcing steel or GFRP alone. Specimen construction included the pier and a portion of the masonry just below the pier. GFRP composite strips were strategically placed to improve flexure and shear strength in the inplane direction. Steel dowels were added to the specimens by drilling down diagonally through the pier and base and securing the dow els with epoxy. This steel was designed to yield prior to rupture of the GFRP composite, giving a ductile response. Improvement in lateral capacity of up to three times the capacity of URM rocking mode was achieved. Drift capacities ranged from 0.29% to 1.6%. Splitting of the masonry was shown to be a controlling factor in the extent of yielding attained in the steel dowels.

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1 CHAPTER 1 INTRODUCTION AND OBJECTIVES Introduction Buildings that are made of wood historica lly, and wood or steel or steel reinforced concrete in recent times tend to fare well when exposed to earthquake induced loads. This is due to the flexibility of wood and the ductility of steel. Steel has the ability to deform large amounts without failing, while dissipating a large percentage of the energy imparted to the building during an earthquake, making it an excellent material for use in areas that may expect earthquake induced loading (whether on buildings made with a completely steel structure or a concrete structur e reinforced with steel). This is especially true in the most recent of modern times (i.e., within the last decade, where structural design and earthquake science have both reached levels of maturity that can make buildings of an unprecedented ruggedness). Prior to the advent of modern reinforced masonry, buildings were constructed with unreinforced masonry (URM) for many years. URM structures do not perform well during earthquakes and can cause significant property damage and loss of life. One reason is that they were designed before structural response to ground motion was well understood. Another reason is that URM construction is inherently brittle and does not provide ductile response during earthquake loading. This lack of ductility can lead to significant local or widespread instability and ultimately, collapse, during ground motion. Thousands of URM structures are currently in service and will remain so for many more years, provided that they do not get knocked over by an earthquake. Engineers

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2 realize today that the chance for devastating earthquakes is greater than has been addressed in the past. Conventional means of strengthening URM structures such as shotcrete have been in use for many years. Other methods include installation of reinforced concrete shear walls or structural steel frames that ignore the contribution of the existing masonry to the load carrying capacity of the structure. Fiber Reinforced Polymer (FRP) composites are made of continuous glass, carbon, or aramid fibers encapsulated in a resin matrix and can be bonded to a masonry surface to strengthen an existing structure. These materials can be added to a building with relatively minor impact on the occupants compared to other methods currently used for building rehabilitation such as shotcreteing wa lls or adding new structural components. It could also be substantially less expensive than methods such as post-tensioning entire walls roof to foundation. This technique has been evaluated by a number of researchers and has been used on URM structures. Several FRP composite manufacturers market systems specifically for application to masonry structures. Ehsani, Saadatmanesh, and Velazquez-Dimas (1999) built three half-scale unreinforced clay brick walls, retrofitted them with vertical FRP strips and subjected them to cyclic out-of -plane loading. They found that the mode of failure was controlled by tensile failure when wider and lighter composite fabrics were used and by delamination when stronger fabrics were used. They report that although URM walls and composites behave in a brittle manner, the combination resulted in a system capable of dissipating some energy. Deflections as much as 2.5% of the wall height were observed for walls with unidirectional fabric; these walls deflected almost 14 times the maximum allowable deflection according to the latest masonry specifications. Some of this energy

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3 dissipation was attributed to the removal of brick material with the composite as it progressively delaminates. Our study observed deflections up to 1.5% for specimens reinforced only with GFRP. Researchers Marshall and Sweeney (2002) performed in-plane shear tests on 4-foot by 4-foot unreinforced double-wythe brick wall specimens and lightly reinforced singlewythe concrete masonry unit (CMU) wall specimens. These specimens were tested with various configurations of glass and carbon FRP applied to them. They found that the strength of the specimens can be increased with the application of FRP composites, however in all cases the failure mode changed to a less ductile mode. They felt that the next step in this line of investigation w ould be to develop configurations of FRP reinforcement that can prevent failure modes such as X-cracking while transferring the failure to a more ductile mode such as bed joint sliding or rocking prior to toe crushing. Holberg and Hamilton (2002) proposed a system incorporating two materials, glass fiber reinforced polymers (GFRP) and st eel, and investigated several configurations on full scale masonry specimens. These utilized two different types of steel connections, internal and external (Figure 1). The drift capacities of these specimens reached up to 1.7%. The lateral capacities were nearly doubled compared to an unreinforced specimen. The vertical GFRP strips are designed to provide enough additional strength to enable the pier to resist the shear and flexural stresses imposed on it during a seismic event. The steel is designed to yield at the pier/sill interface prior to failure of the GFRP composite.

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4 Lateral Load FRP improves shear and flexural strength Steel bonded between pier and sill adds ductility Figure 1: Pier strengthened with FRP. Research Objectives The intent of this research is to further develop and evaluate the rehabilitation mechanism utilizing a hybrid system for the reliable dissipation of energy within a brick building during a seismic event. Previous URM research has focused primarily on pier segments. This approach inherently directs the focus on the pier without examining the behavior at the pier interface. Figure 2 shows an illustration of the pier and base portion of a building that was used to develop the specimen configuration for the tests performed in this research. This area was chosen for modeling because it is the area of a building that is most susceptible to damage during a seismic event. Various methods of anchoring the pier to the base were investigated. Base Pier Figure 2: Model for specimens

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5 The system under investigation consists of GFRP and steel added to strategic areas of a brick wall. The GFRP can add strength where it is desirable while the steel can provide ductility to the system. Properly placed GFRP has the potential to direct seismic energy to the added steel, allowing it to be dissipated through the ductility of the steel.

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6 CHAPTER 2 EXPERIMENTAL PROGRAM Eight clay brick specimens were constructe d and tested. The behavior of the pier ductile connection and base subjected to in-plane cyclic loading was investigated. The experimental parameters were the amount and type of GFRP composites and the amount of steel which was added to the basic wall specimen. Test Specimens The specimens were constructed in running bond using type N mortar. A local masonry contractor (Painter Masonry, Inc.) was hired to build the wall specimens. ASTM C62 grade MW 8 inch clay bricks were obtained locally from Florida Rock Industries Inc, located in Gainesville FL. Double-wythe construction gave a thickness of 8 in. (203 mm). The outline of the specimens consisted of a 48-in. square pier resting on a 112 in. (2.8 m) long by 16-in. (0.4m) tall base (Figure 3). Precast concrete lintels were used to support and move the specimens. The lintels were reinforced longitudinally with two no. 6 steel reinforcing bars and filled with readymixed concrete. The length of the base lintels was 112 inches (9 feet, 4 inches). A second lintel was set on the top of each pier using the type N mortar. A header course was laid at the fourth course and at each sixth subsequent course. Collar joints were filled solid with mortar. The first course in Specimen I was laid with half-length units at each end instead of the full length shown in Figure 3. It is believed that this minor coursing difference did not effect the performance of the specimen.

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7 64 in. 48 in. 48 in. pier 16 in. base 64 in. Lifting holes Precast concrete lintel Precast concrete lintel (1.6 m) (1.2 m) (1.2 m) (0.4 m) Figure 3: Configuration of specimens Material Properties Materials used for building the walls were tested individually to determine their characteristics (Table 1). Individual brick units and prisms made with four units were tested in compression to failure. The prisms were made using the mortar from the batches used to construct the walls. The #3 steel rebar and the unidirectional fiberglass were tested in tension until fracture. These tests were performed to ASTM standards. All tested samples were taken randomly from stock. The GFRP samples were cut from a section of cured GFRP composite and then milled to a 1 in. width. The average width of these was 1.04 in. (26.4 mm) and the average thickness was 0.09 in. (23.1 mm). Preparation and testing of the GFRP followed ASTM D3039.

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8 Table 1: Material Properties Material Test Average Strength No. of Specimen Bricks Unit compressive strength 7790 psi (54 MPa) 7 Brick Prisms Prism compressive strength 4230 psi (29 MPa) 7 #3 Steel rebar Tensile yield strength 62 ksi (427 MPa) 4 GFRP #3 rebar Mfgrs. specs. tensile strength 110 ksi (758 MPa) na GFRP unidirectional coupons Tensile strength 2.8 kips/in. width (500 N/mm) 5 GFRP bond GFRP tensile bond strength Wire brushed 706 psi (4.9 kPa) Sand blasted 801 psi (5.5 kPa) 4 3 Pre-preg GFRP Mfgrs specs. tensile strength 1.2 kips/inch (210 N/mm) na Glass Fiber Reinforced Polymer Reinforcement Six of the eight specimens were strengthe ned with varying widths and lengths of GFRP laminate, 27 oz/yd2 (7.5 N/m2), bonded to the brick surface with a twopart epoxy. The walls were either cleaned with a power wire brush or sandblasted and then brushed clean prior to the application of the GFRP. One of the specimens was reinforced with spray-on chopped fiberglass/resin and reteste d. The seventh specimen was strengthened with a unidirectional grid of pre-impregnated fiberglass. This is a high strength material made by bonding E-glass fiber rovings with epoxy resin in a controlled factory environment. It was bonded to the specimen using a low modulus two-part epoxy. The eighth specimen was reinforced with near-surface mounted #3 GFRP bars. Quantity and placement of the GFRP for the pier and base were determined using a strut and tie analysis and basic principles of mechanics. Figure 4 shows the location of the general placement of the GFRP laminates and Table 2 details GRFP composite configurations and placement. Testing of specimen 1h resulted in very little damage to

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9 the masonry (laminate A debonded). Consequently, the specimen was revised (specimen 1i). Chopped fiber spray up system was applied to the north face and the specimen was retested. E D A B C (2 PL) Figure 4: General GFRP laminate placement The vertical strips (A) increased the in-plane flexural strength and the diagonal strips (D) increased the diagonal tensile strength of the pier. (A) was 3 inches wide on all specimens where used except test 2 which was two inches and test 6 which was 6 inches of the GFRP grid. The vertical strips of chopped glass spray-up for test 1i were 8 in. wide. (D) was 3 inches wide where used except on test 6 which was 7 in. of GFRP grid. Bi-directional GFRP laminate (grid for test 6) was added across the top of the pier (E) at the pier/lintel interface (12 in. x 48 in.) to reduce the likelihood of a separation of these two components during testing. Laminate B (6 in. x 112 in.) provided be nding resistance and laminate C (18 in. x 112 in.) provided shear resistance in the base of the specimen. Table 2 shows the complete GFRP patterns for the individual specimens. The chopped fiberglass shown on the specimen for test 1i is labeled (F). The pre-impregnated grid is labeled (G) on the specimen for test 6 and the helical wrap glass rebar for the specimen for test 8 is labeled Glass Rebar.

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10 Table 2: Glass Fiber Reinforced Polymer configuration Tests 1h to 5 Specimen North Face South Face 1h E D A B C (2 PL) 1i F C B E D A B C (2 PL) 2 E A B C (2 PL) E D A B C (2 P L 4 E D A B C (2 P L E A (2 PL) C B 5 D A B C (2 PL) No GFRP on south face

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11 Table 2: GFRP configuration (cont.) Specimen North Face South Face 6 G (ALL STRIPS) No GFRP on south side 7 E D A B C (2 PL ) No GFRP on south side 8 GFRP NSM 7 PL No GFRP on south side 9 C B A (2 PL) No GFRP on south side Steel Reinforcement Steel reinforcement (#3) was installed in specimens for tests 2, 4, 7, and 9 in an attempt to achieve a ductile failure. The size and number of bars chosen were coordinated with the amount of GFRP used so that the steel would yield prior to a failure of the GFRP composite. Steel reinforcing bars were installed as shown in Figure 5 by drilling a in. diameter hole diagonally down, starting on the pier (broad face) 16 inches up from the pier/base and down through the wall to emerge at the bottom of the base on the far side of the wall (Figure 5). Each hole was filled with a two-part, high-modulus epoxy (Master Builders Concresive 1420) by inserting a tube to the bottom of the hole and withdrawing

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12 it as the epoxy was injected through it. The reinforcement was then coated with epoxy as it was inserted into the hole with strain gauge wires coming out of the top of the hole. The strain gauges were covered with tape and shrink wrap tubing for a length of four inches. This gave a four inch unbonded length of the steel to the brick allowing the steel strain to be distributed over this four inch length. Figure 2-3 shows the location of the added steel. Pier Base N O. 3 REBAR 6 in. (test 4 only) 4 in. 16 in. 16 in. No. 3 rebar pier base Tests 2, 4, 7, & 9 pier base 16 in. 16 in. epoxy #3 bar 4 in. (100mm) unbonded length Unbonded section of bar Figure 5: Location and orientation of steel reinforcement

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13 Test Setup The test setup was designed to load the masonry specimens in plane (Fig. 1). The inverted T configuration, representing th e lower half of a wall pier between two windows, required tie-down points at each end. A 55 kip MTS hydraulic actuator was placed between the top of the cap and the reaction frame. This actuator was part of a closed-loop hydraulic loading system. The system was controlled by an MTS 407 controller. The controller used a sinusoidal voltage output from the data acquisition system to impart the desired displacements to the cylinder. The actuator has a built-in load cell ( a + reading is specimen pulled to the West, a reading is pushed to the east) that was used to acquire the load imposed on the specimens during testing. Extension and retraction of this device simulated the loading conditions that would be experienced by a shear wall during ground movement parallel to the wall. Figure 6 shows the testing setup and configuration. 4 KIP/IN SPRING (QTY 2) STRONG FLOOR (THICK REINFORCED CONCRETE SLAB) 50 KIP HYDRAULIC ACTUATOR REACTION FRAME ALL THREAD ROD ALL THREAD ROD East West 2000 # CAP CONCRETE BASE Figure 6: Test setup view from the North

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14 Part of the gravity load was simulated by applying a downward force of 6.0 kips to the concrete cap with two pre-compressed rail car springs. This force combined with the weight of the concrete cap (2.0 kips [8.9 kN] ), pier, and lintel gave a load of approximately 9.0kips (40 kN), creating an axial stress of 25 psi (172 kN). National Instruments LabVIEW software was run on a personal computer along with a 16 bit data acquisition card for data acquisition. Linear and string potentiometers were used to measure wall displacements. Foil strain gauges were applied to the steel and GFRP to measure their strains. Test Procedures The ICBO Acceptance Criteria for Concrete and Reinforced and Unreinforced Masonry Strengthening Using Fiber-Reinfor ced Composite Systems (ACI125) (ICBO 1997) was followed to determine the displacements to be imposed for each test. For walls with no steel the yield point was taken as the displacement that was expected to cause cracking and initiate rocking of an unreinforced specimen. For walls with steel reinforcement, yield was taken as the displacement at which the steel was expected to yield. These yield displacements were assigned = 1. The displacements then imposed during testing were fractions or multiples of = , 1, 2, 3, 4, 6, 8, 10, 12, 16, etc. The specimens were loaded in displacement control with three complete cycles for each displacement level A complete cycle was one displacement in each of the positive and negative directions. The specimens were loaded through increasing until lateral load carrying capacity was lost or the specimen was deemed unstable.

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15 Instrumentation Figure 7 shows the location of either the instrument itself or the attachment point to the wall for the instrumentation that was common to all specimens. The type of each device shown is listed in Table 3 along with the measurement taken. Each device was either mounted to the wall with its probe contacting or attached to a solid stand or the device was mounted to a stand with its probe contacting or attached to the wall. The figure does not necessarily show the location of the instrument but the location where the measurement is being taken. The locations of GFRP and steel strain gauges are shown in Figure 8 to Figure 13. All stands were heavy and solidly connected to the lab floor. Carol and Diane were located as shown for several tests and then moved to the west side (same relative location) for the remainder of the tests. The naming convention for the instruments was chosen in order to give each instrument a unique identity, facilitating their placement and setup. Carol Flo (oop) Will Diane Emily Karl Jim Henry Ian Vanessa (oop) GinaEast West (oop = out of plane) Figure 7: String and linear pot location for all walls

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16 Table 3: Instrument type and function Name Type Measurement Shown Carol String pot Horizontal Displacement in plane Attach point Gina String pot Vertical Displacement in plane Attach point Flo String pot Vertical Displacement in plane Attach point Emily Linear pot Horizontal Displacement in plane Instrument Diane String pot Horizontal Displacement in plane Attach point Will Linear pot Horizontal Displacement out of plane Contact point Vanessa Linear pot Horizontal Displ acement out of plane Contact point Ian Linear pot Vertical Displacement in plane Instrument Henry Linear pot Vertical Displacement in plane Instrument Karl Linear pot Vertical Displacement in plane Instrument Jim Linear pot Vertical Displacement in plane Instrument Linda Strain Gauge Vertical strain FRP or glass rebar Nancy Strain Gauge Horizontal strain FRP or glass rebar Marie Strain Gauge Vertical strain FRP or glass rebar Oscar Strain Gauge Steel strain Pete Strain Gauge Steel strain Quin Strain Gauge Steel strain Rick Strain Gauge Steel strain Linda Nancy Marie (1h, 1i, 6 only) Figure 8: GFRP strain gauge locations for Specimen 1h, 1i, 5, 6

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17 Oscar Pete Figure 9: Steel strain gauge locations for Specimen 2 Oscar Pete Rick Quin Linda Nancy Figure 10: GFRP and steel strain gauge locations for Specimen 4 Oscar Pete Linda Figure 11: GFRP and steel strain gauge locations for Specimen 7 Linda Marie N ancy Figure 12: Glass rebar strain gauge locations for Specimen 8

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18 Linda Oscar Pete Figure 13: GFRP and steel strain gauge locations for Specimen 9

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19 CHAPTER 3 EXPERIMENTAL RESULTS Specimen Behavior Cyclic behavior of each specimen is illustrated in the loaddrift plots shown in Figure 14 through Figure 22. A single test was performed on each specimen. Consequently, test numbers correspond directly with the specimen numbers described in previous sections. Drift was calculated as the in-plane displacement of the pier divided by its height. Horizontal lines have been added to the plots that indicate the loads at which the GFRP was calculated to rupture for specimens with no steel and the loads at which the steel was calculated to yield for specimens with added steel. Details of the calculations are presented in a later section. -20 -10 0 10 20 -2-1012 Drift (%)Load (kips)-89 -44.5 0 44.5 89Load (kN) Figure 14: Cyclic behavior of Test 1h GFRP laminate only

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20 -20 -15 -10 -5 0 5 10 15 20 -2-1012 Drift (%)Load (kips)-89 -44.5 0 44.5 89Load (kN) Figure 15: Cyclic behavior of Test 1i Specimen 1h repaired with spray-up GFRP -20 -10 0 10 20 -2-1012 Drift (%)Load (kips)-89 -44.5 0 44.5 89Load (kN) Figure 16: Cyclic behavior of Test 2 GFRP laminate, 2-#3 reinforcing steel bars -20 -10 0 10 20 -2-1012 Drift (%)Load (kips)-89 -44.5 0 44.5 89Load (kN) Figure 17: Cyclic behavior of Test 4 GF RP laminate, 4-#3 reinforcing steel bars -20 -10 0 10 20 -2-1012 Drift (%)Load (kips)-89 -44.5 0 44.5 89Load (kN) Figure 18: Cyclic behavior of Test 5 GFRP laminate only

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21 -20 -10 0 10 20 -2-1012 Drift (%)Load (kips)-89 -44.5 0 44.5 89Load (kN) Figure 19: Cyclic behavior of Te st 6 GFRP Pre-impregnated only -20 -10 0 10 20 -2-1012 Drift (%)Load (kips)-89 -44.5 0 44.5 89Load (kN) Figure 20: Cyclic behavior of Test 7 GF RP laminate, 2-#3 reinforcing steel bars -20 -10 0 10 20 -3-2-10123 Drift (%)Load (kips)-89 -44.5 0 44.5 89Load (kN) Figure 21: Cyclic behavior of Test 8 GFRP #3 reinforcement -20 -10 0 10 20 -2-1012 Drift (%)Load (kips)-89 -44.5 0 44.5 89Load (kN) Figure 22 Cyclic behavior of Test 9 GFRP laminate, 2-#3 reinforcing steel bars

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22 Table 4 gives peak lateral loads and limiting modes of failure for each test. The peak loads were the maximum force detected during the cycling and do not necessarily correspond to the maximum drift ratios shown. The maximum drift ratios were determined by taking the maximum lateral movement achieved at the top of the specimen and dividing it by the height of the pier (48 in.) and multiplying this by 100. Table 4: Results of cyclic testing Test Maximum Drift (%) Maximum Lateral Load (kips) Limiting Mode 1h + 0.29 0.29 + 9.88 10.25 GFRP bond failure Pier rocking 1i + 0.39 0.36 + 17.76 18.07 GFRP rupture Pier rocking 2 + 0.96 1.32 + 15.04 12.87 Diagonal tension Pier rocking 4 + 0.58 0.51 + 17.57 17.66 Pier rocking Tensile failure of brick 5 + 0.50 0.52 + 11.95 11.78 Pier rocking GFRP rupture 6 + 1.26 1.29 + 15.40 15.56 Pier rocking 7 + 1.01 1.02 + 13.73 12.31 Pier rocking Diagonal tension 8 + 1.54 1.62 + 10.10 11.20 Mortar joint tensile failure in base 9 + 0.65 0.78 + 11.51 10.36 Mortar joint tensile failure in base The following presents a brief summary of the behavior of each specimen during cyclic testing. Observations are keyed to the displacement ratio or % drift. For these discussions debonding is a separation at the laminate-masonry interface; substrate failure is a cohesive failure in the masonry; and delamination is a separation of laminate layers. Test 1h: Specimen damage initiated at = (drift = 0.28 %)with debonding of GFRP laminate A. The debonding initiated at the Pier/Base interface, debonding

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23 commencing at = 1/2 and progressing from interface, and progressed incrementally with each displacement cycle. This prevented the intended failure mode from occuring, which was rupture of A at the pier/base interface. Laminate A was completely debonded at 0.48 % drift at which point the test was terminated. It was thought that perhaps out-of-plane movement occured due to eccentric reinforcement (GFRP strips placed on one side only). The measured out-of-plane movement, however, was only 0.005 in. (0.13 mm) at 0.09 % drift, which is probably too small to have initiated the debonding. To address this question, the pull-off bond strength of the GFRP composite was investigated. Two-in. (50mm) diameter disks were adhered to the surface of the GFRP composite. A core drill with the same diameter as the disk was used to cut through the GFRP composite and lightly into the brick. The force required to pull the disk off of the masonry was measured. These tests were performed on two differently prepared brick surfaces, one was sandblasted and the other wire brushed with a power wire brush. Failure modes were cohesive through the brick indicating adequate bond. The material tested for bonding was the + or 45 degree weave material while the GFRP that peeled off during wall testing was the unidirectional glass. After laminate A debonded completely, the specimen reverted to a rocking response mode, causing very little damage. Consequently the specimen was repaired with a spray up system described previously. Test 1i: After completion of test 1h, spray on chopped fiberglass was applied to the face opposite that of the GFRP laminate. Spray-on GFRP began cracking at the pier/base interface on the east edge of the west strip. Cracks were first noted at 0.21 %

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24 drift and were oriented parallel to the bed joints. This cracking progressed upward along the east edge of the strip as displacement increased. GFRP rupture occurred approximately 12 inches above pier/base interface at 0.54 % drift. The decrease in lateral capacity associated with rupture is evident in the negative drift quadrant of the plot (Figure 15). Excellent bond of the resin to the brick was displayed by the high stiffness and lack of debonding prior to GFRP rupture. Test 2: The wall cracked diagonally above one reinforcement and vertically/slight diagonal next to the other one, first crack occurring at = 1 (0.11 % drift). It cracked across the base of the pier and across the wall at the top of the reinforcement (Figure 23). The exterior crack pattern reflects brick/reinforcement bond failure and splitting of the brick. Figure 23: Crack pattern for test 2 (North face) A combination of GFRP debonding in laminate A and substrate failure occurred at base of pier at 1.44 % drift. GFRP that came loose had pieces of brick stuck to it. Mechanical bond failure (splitting) occurred and is shown in Figure 24. First steel yield was detected at 0.14 % drift. This specimen had the best performance when considering ductility. Steel yielding continued until bond failure.

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25 A B Figure 24: A Test 2, east edge of pier. B Test 4, south side east edge of pier Test 4: Cracking was first observed at 0.14 % drift in a pattern similar to that observed in test 2. The brick starts to split around the outer reinforcement and the load redistributes and is picked up by the inner rein forcement, indicated by the slight flat spot in the positive quadrant of load vs. drift and the drop of load in the negative quadrant. Strains beyond yield were detected in the last cycle, explaining the more open loops in the negative direction (Figure 17). Cracks in the pier coalesced into a single crack surrounding the steel reinforcement. This resulted in the sharp drop in load and subsequent rocking behavior displayed in the plot. Rocking motion resulted in permanent movement as indicated by Diane (Figure 25) and the gap in the vertical crack (Figure 24).

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26 0.0 0.5 1.0 -0.6-0.4-0.20.00.20.40.6 Displacement (in.)Diane (in.) Figure 25: In-plane movement base of pier Test 5: Pier cracked between the top of the reinforcement and the pier/base interface. Cracking was first observed at 0.26 % drift. The vertical GFRP at both edges debonded at 0.75% drift starting at the pier/base interface and moving upward during the last cycle of loading and finally ruptured at pier/base at east end. GFRP debonded and pulled off pieces of brick at west end. Rock ing is indicated by bi-linear curve in LoadDrift plot. Test 6: Cracking was first observed at = 6 (Drift = 0.53 %). This delayed onset of cracking can probably be attributed to the large area coverage of the GFRP which would distribute the stresses evenly across the brick. This could be an advantage holding a building together. Brick and mortar in the pier/base area failed through successive cracking on the side away from the GFRP applied surface. Ultimate load carrying capacity was lost due to rupture of grid which occurred at pier/base interface and a drift of 1.79 %. No visible damage occurred to the GFRP prior to rupture. The flexibility of the low modulus epoxy is indicated by the increasing load capacity in the second portion of the bi-linear curve in the LoadDrift plot Test 7: Cracking was first observed in bed joint at pier/base interface. During subsequent displacements cracks appeared in the bed and head joints between the top of the reinforcement and the base with the cracks progressing across the wall. A and D

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27 laminates started debonding from the brick at the pier/base interface at 0.18 in. displacement (0.30 % drift) and continued up the wall incrementally with increasing displacement. This was intermittently spaced, however, and both vertical strips remained bonded to the brick at the lower ends until the last cycle at which both strips pulled away from the wall, taking pieces of brick with them. Test 8: Initial cracking was first observed at = 1 (0.12 %). The base failed through a combination of flexure plus cone pull-out (diagonal tension). Figure 26 shows the crack pattern that developed in the specimen. The cone pull-out is indicated by the diagonal cracking alongside the vertical bars and the flexure is indicated by the cracking along the bottom of the base. It is notable that the pier sustained no cracking. INSTL. CRACK INSTL. CRACK Figure 26: Crack pattern for test 8 Near complete loss of anchorage resulted in a restrained rocking response. Some anchorage capacity remained because of the GFRP bar B. Strain measurements (Figure 27) indicate that the bar was contributing somewhat to the anchorage restraint. Load measurement, however, indicates only a slight increase in lateral force over that of pure rocking response. The steep drop in load in the negative quadrant of the Load diagram indicates a complete loss of anchorage due to the greater concentration of local cracking around the north GFRP bars. The positive glass strains shown on strain diagrams for

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28 positive and negative displacement are due to the fact that the vertical reinforcement is always on the tension side of the neutral axis. 0 2000 4000 6000 8000 -2-1012 Drift (%)GFRP bar strain (uE) Figure 27: Strain measured in GFRP bar A at north end of pier. Test 9: The pier stayed together as a unit and exhibited no noticeable cracking. The strain in the reinforcement at the east end (bar is in tension during positive load) and the load dropped off simultaneously (at 0.24 % drift). At this displacement the vertical cracking and the bed joint cracking at the pier base occurred (Figure 28). Figure 28: Crack pattern for test 9 Continued positive loading caused the base to lift up and the pier to rock. The reinforcement may have just reached yield as the base started breaking up. This is notable as it indicates the practical limit to the amount of steel that it is useful to add. For negative loading it appears that the tension reinforcement was pulling out of the hole. This would explain the small amount of steel strain along with the small amount of

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29 uplifting of the base while the pier uplift is much greater. The strange bulb shape in the negative quadrant of the Load diagram shows that the weight of the pier would induce negative load during bar slippage even though negative displacement was decreasing It was noticed during specimen demolition that the epoxy holding this reinforcement was not cured hard. Its color was not typical and incomplete mixing is suspected. The pier and base both walked to the east. Load-Displacement Envelopes A backbone curve was developed for each specimen. These are compiled in Figure 29 and Figure 30. The acceptance criteria for new materials in FEMA 273 were used to develop these curves. -20 -10 0 10 20 -2-1012 DisplacementLoad (kips)Test 1i Test 8 Test 6 Test 5 Test 1h Figure 29: Backbone curves specimens with no steel -20 -10 0 10 20 -2-1012 Displacement (in.)Load (kips)Test 4 Test 9 Test 7 Test 2 Figure 30: Backbone curves specimens with steel

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30 The behavior indicated by these plots can be modeled by the force-displacement graph shown in Figure 31. It has been suggested by Moon, Leon et al. (2002) to take the initial uncracked stiffness of the specimen as k After cracking the stiffness can be represented as a reduced stiffness, k caused by a combination of cracking, yielding, and damage to the specimen. If the GFRP composite bond is inadequate then the specimen stiffness can be reduced further. The second, lower stiffness branch of the curve represents a lowered stiffness due to bond failure. Failure of the GFRP composite is shown by the dotted representing a large reduction in strength. Beyond this point the strength of the specimen is represented by the horizontal and is equal to the strength of an unreinforced specimen. L o a dAdequate FRP bond Inadequate FRP bond k k Unstrengthened capacity k Drift (%) Figure 31: Force-displacement curve for Unreinforced Masonry strengthened with fully bonded GFRP composite and inadequately bonded GFRP composite Ductility Of Masonry Systems The focus of this research was to assess several methods of strengthening unreinforced masonry using GFRP composites Some of the methods involved a hybrid system which combined steel and GFRP composites. FEMA 273 outlines requirements

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31 for assessing the ductility of new materials. System or component ductility is quantified by equation 3-1. mkQCE QUD (3-1) QCE = Resistance capacity QUD = Seismic demand k = Knowledge factor relative to material property uncertainty m = Component demand modifier Ductility capacity coefficient Equivalent lateral force procedures are used to determine component and system capacity with this equation. The value of m increases proportionally with an increase in system or component ductility. Lateral load demand is reduced through inelastic response. When determining m for reinforced masonry, as outlined in FEMA 273, it is assumed that the reinforcement is a ductile material. These types of material are referred to as deformation controlled. Materials that fail in a brittle manner (exhibiting linear stiffness up to severe loss of capacity) are considered force controlled. Individually masonry and GFRP are brittle materials and would be force controlled but when used together they behave similarly to a deformation controlled system. Damage sustained by the system, without going to failure, dissipates energy and increases displacement capacity. The bilinear stiffness shown in Figure 31 shows this type of behavior. FEMA 273 m factors are determined from force deformation curves and are applicable only to systems or components with steel reinforcement, these representing a minimum ductility. The m factors were calculated for the steel reinforced specimens of this current research using this process and are shown in Table 5.

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32 A moment-curvature analysis was performed to quantify the ductile nature of the specimens that were reinforced with GFRP only. The factor derived with this method has been termed curvature ductility, and fundamentally differs from the determination of m only in that cracking was used for the analysis rather than yielding. Curvature ductility factors are given in Table 6. Table 5: m factors per FEMA 273 for specimens with steel m -factor Test Immediate Occupancy Life Safety 2 + 5.0 6.8 + 3.7 5.1 4 + 6.6 6.9 + 5.0 5.2 7 +14.8 11.1 + 11.1 5.2 9 + 15.4 16.9 + 11.5 12.7 Table 6: Curvature ductility factors specimens reinforced only with GFRP. Ductility FactorsMoment Curvature Analysis Test 1h 7.14 5 4.6 6 3.0 8 4.5 was determined by dividing the ultimate curvature, Cu by the curvature at first cracking, Ccr then multiplying this quantity times the ratio of the moment at cracking, Mcr divided by the ultimate moment, Mu: = (Cu Mcr) / (Ccr Mu) (3-2)

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33 The values were obtained graphically from a moment curvature diagram for each specimen using the procedure outlined in Paulay and Priestly (1992). The process used for specimen 1h is shown in Figure 32. Curvature M o m M u M cr C'crCcrCu Figure 32: Method for obtaining values to calculate curvature ductility Analytical procedures developed by Pauley and Priestley (1992) have been adopted in FEMA 273 to determine displacement ductilities ( ) from curvature ductilities. This method considers plastic rotations at the base of the component to be limited to a plastic hinge length, lp, equal to: lp = 0.2 L + 0.04 heff (3-3) where L is the length of the wall and heff is the height of the wall from the base to the lateral force. Displacement ductility is then determined as: = 1 + 3( 1)( lp/ L )(1 0.5 lp/ L ) (3-4) Computing Predicted Capacities Holberg and Hamilton (2001) describe a methodology for the calculation of the flexural capacity of specimens of the type used in this research. Such capacities were calculated for two critical sections for the specimens in this study. These sections are 1) where the GFRP composite ends and the flexural capacity is provided by the steel only and 2) where the vertical GFRP at the pier edges provide the flexural capacity. Figure 33 shows this relationship. In this figure Pw is the self-weight of the pier and concrete cap,

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34 Ps is the axial force provided by the springs, and Q is the lateral load carrying capacity of the section. The flexural capacity at either of the critical sections is determined using principles of mechanics and the traditional rectangular stress block assumption. For an under reinforced condition, the depth of the stress block, a is: a = ( Asfy +Ps + Pw) / 0.85 fmbe (3-5) be = effective thickness of masonry As = cross sectional area of steel fy = yield of steel fm = compressive strength of masonry The moment capacity, Mnbar of the section where the steel provides the flexural strength is calculated by applying equilibrium to the section: Mnbar = Asfy ( d a/ 2) + ( Ps + Pw)( l /2 a/ 2) (3-6) The load required to yield the steel, i.e. the lateral capacity, is: Q = Mnbar/ heff (3-7) The moment capacity, Mnfrp, of the critical section for specimens with no steel is taken at the pier/base interface and is calculated in a similar manner: a = ( T w + Ps + Pw) / 0.85 fmbe (3-8) Where: T = tensile strength of the GFRP composite per inch width, and w = width of the composite strip. Then, the moment capacity is given by: Mnfrp = T w ( d a/ 2) + ( Ps + Pw)( l /2 a/ 2) (3-9) Q = Mnfrp/( heff ls) (3-10)

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35 Q PS PW lsCritical Section Mnfrp Critical Section Mnbar d l h eff Figure 33: Schematic for predicting specimen capacity Table 7 shows the ratio of the measured lateral force, Qm, at steel yield or GFRP rupture, to Qnbar or Qnfrp along with the calculated capacities. It can be seen that the predicted capacity is close to the measured capacity for all specimens except 6 and 7 which is an indication of the accuracy of the equation. Table 7: Measured and Calculated Lateral Capacities Test Measured Capacity Qm (kips) Qnbar (kips) Qnfrp (kips) Ratio ( Qm/ Qnbar( Qnfrp)) 1h + 9.88 10.25 8.61 1.15 1.19 1i + 17.76 18.06 na na 2 + 15.04 12.87 11.33 1.33 1.14 4 + 17.57 17.66 14.8 1.19 1.19 5 + 11.95 11.78 8.89 1.34 1.33 6 + 15.40 15.56 9.0 1.71 1.73 7 + 13.73 12.31 7.8 1.76 1.58 8 + 10.10 11.20 11.5 0.88 0.97 9 + 11.51 10.36 8.0 1.44 1.3

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36 CHAPTER 4 CONCLUSIONS Eight clay masonry specimens simulating the pier area between two windows of a low-rise unreinforced brick building were built. These specimens were then modified to represent a potential rehabilitation to enhance their ability to withstand an earthquake. The modifications added strategically placed steel rebars and FRP composite strips, FRP composite strips, or FRP rebars. When steel was added it was designed to yield prior to the added FRP rupturing. These modifications show good potential for rehabilitating unreinforced brick structures to withstand a seismic event. Further research conducted with similar configurations could help quantify the ductility improvement and help develop appropriate m -factors for reducing seismic demand. Key findings and conclusions: Rehabilitation of an unreinforced brick structure with steel and FRP composites resulted in an improvement in ductility, lateral capacity, and energy dissipation. A drift ratio of 1.64% and a lateral load capacity of almost 18 kips was achieved. This is 2.4 times the lateral capacity of an unreinforced specimen. Energy dissipation as the steel yielded was indicated by the open loops in the loaddisplacement plots. Although it would be desirable to be able to perform modifications to one side only of a building, it is seen by the performance differences between test 2 (two sides of wall, 15.7 kip ultimat load, 1.63 % drift) and test 7 (one side of wall, 13.67 kip ultimate load, 1.52 % drift) that adding GFRP to both sides gives superior results. Adding GFRP to the base provides desirable strengthening. The specimen for test 8 had no base reinforcement and broke apart while the base held together on specimens where it was reinforced.

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37 APPENDIX A LITERATURE REVIEW M. R Ehansi, H. Saadatmanesh, and J. I. Velazquez-Dimas (1999) Behavior of Retrofitted URM Walls Under Simulated Earthquake Loading These researchers built three half-scale unreinforced clay brick walls, retrofitted them with vertical FRP strips and subjected them to cyclic out-of -plane loading. Five reinforcement ratios and two different glass fabric composite densities were investigated. They found that the mode of failure was controlled by tensile failure when wider and lighter composite fabrics were used and by delamination when stronger fabrics were used. They report that although URM walls and composites behave in a brittle manner, the combination resulted in a system capable of dissipating some energy. Some of this energy dissipation was attributed to the removal of brick material with the composite as it progressively delaminates. J. Gustavo Tumialan, Angel San Bartolome and Antonio Nanni (2003) Strengthening of URM Infill Walls by FRP Structural Repointing This paper presents results of a testing program dealing with the in-plane behavior of URM infill walls subjected to in-plane cyclic loading. Four full-scale infill walls were constructed with unreinforced hollow concrete units inside a reinforced concrete (RC) frame. One stand-alone (RC) frame was built. The purpose of building and testing this frame was to determine its stiffness and capacity and therefore to assess the change in behavior of the lateral force resisting system due to the presence of the masonry infill.

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38 The RC frames were built to be ductile enough that the behavior of the lateral force resisting system would be controlled by the infill masonry and not the RC frame.One wall was tested in the unstrengthened condition. Two walls were tested after strengthening by structural repointing. Th is method embedded 6.25 mm GFRP bars in hollowed out bed joints filled with epoxy paste. The fourth wall was reinforced internally by cutting holes in the top layer of blocks, inserting 6.25 mm GFRP bars into the vertical cells (spacing of 400 mm) and then filling the cells with grout. There was no horizontal reinforcement. Conclusions: FRP strengthened specimens reached lateral drifts of 0.7 % with no loss of lateral load carrying ability. There was however, some loss in lateral stiffness with increasing drift. FRP strengthened specimens exhibited more but finer cracks than the unstrengthened specimen. For lateral drifts greater than 0.5% the absorbed energy decreases in the unstrengthened wall while it increases in the other walls. At 0.7% drift the energy absorption capacity was 40% greater for the strengthened walls. Absorbed energy was calculated as the area under the loading portion of the load vs. displacement curve for each phase of loading. Gustavo Tumialan, Nestore Galati, and Antonio Nanni (2002) Flexural Strengthening of Unreinforced Masonry with FRP BarsThese researchers investigated the behavior of four 24 wide by 48 tall by 3.75 thick initially unreinforced hollow concrete unit specimens subjected to out of plane loading. Three were retrofitted with varying amounts of n ear surface mounted (NSM) GFRP bars and the fourth had a 3 wide strip of externally bonded GFRP laminate the height of the wall applied. NSM involved cutting vertical grooves the height of the walls and bonding the bars into the grooves with epoxy paste. The laminate wall reinforcement was equivalent

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39 to the NSM wall with one bar in terms of ax ial stiffness (Modulus of Elasticity of GFRP x Cross Sectional Area). Conclusions: Strengthening masonry walls with GFRP bars can substantially increase out-ofplane flexural strength and pseudo-ductility. The original flexural capacity of masonry can be increased by 4 to 14 times. The researchers opine that these values should be taken as reference only in walls that can be idealized as simply supported. A masonry wall strengthened with NSM GFRP bars exhibited similar performance to a wall strengthened with GFRP laminates. A. M. Holberg and H. R. Hamilton III (2001) Strengthening URM with GFRP Composites and Ductile Connections Researchers investigated the behavior of simulated low-rise masonry building piers retro-fitted with FRP and discrete steel reinforcement. The FRP was added to help resist shear and flexural stress. The steel was added to increase the ductility and lateral load capacity of the system. Specimens were subjected to in-plane cyclic loading applied with a hydraulic actuator. Test specimens were four full-scale single-wythe hollow concrete unit walls laid in running bond with full mortar bed. The GFRP laminate was formed with unidirectional glass fiber bonded to the walls with two-part epoxy. Added steel reinforcement was of two types, both intended to transfer uplift from the edges of the specimen to a concrete base. One was an external system in which GFRP strips bonded to the wall were placed under a steel angle/plate configuration which was bolted to the floor. Uplift forces in the glass strap would induce bending in the steel plate, which was designed to yield before failure of the strap. The other steel retrofit was no. 3 steel rebars installed inside the blocks by removing face shells at both edges of the wall and after bar insertion filling the cells with grout. The bar was bonded with epoxy into a hole drilled in the

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40 concrete base. This steel was also sized to yield prior to the failure of the FRP. One wall was not retrofitted (no. 1). Unanticipated problems occurred which included a premature pullout of the internal rebar from the concrete base, the failure of the FRP where it was bent around the steel angle, and bottoming out of the springs used to apply gravity load. Additional springs were later added in series. In spite of these problems useful data was obtained. Lateral capacity was increased from 3.3 kips for no. 1, to from 5.7 to 5.9 kips for the retrofitted specimens. The test was terminated at 0.1 % drift for no. 1 prior to what would have been maximum drift. Retrofitted specimens reached 0.6% to 1.7% maximum drift. All retrofitted specimens showed energy dissipated by the added steel. This was indicated by the open hysteretic loops in the Load vs. Drift plots. Kunwar Bajpai and Dat Duthinh (2003) Bending Performance of Masonry Walls Strengthened with Surface Mounted FRP Bars These researchers investigated the behavior of concrete masonry beams subjected to four point bending, simulati ng out of plane bending of a wall. These beams were reinforced with various amounts of FRP bars on the tensile face of the beams. Beams were either two units wide or four units wide and 9.33 feet long. The bars were installed in inch square grooves cut into the masonry surface either parallel or perpendicular to the mortar bed joints, one bar in a narrow beam and three in the wide beams. Prior to the flexural tests, bond tests were conducted on two sizes of FRP bars inch and 3/8 inch diameters and three adhesive types two epoxies and one latex modified mortar. One of the epoxies prove d superior for bonding the FRP to masonry. This adhesive was used for another set of tests, which showed that bars which were

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41 sand-coated with a helical fiber tow achieved higher bond strengths than bars with circular ribs on a smooth surface. It was also determined that smaller diameter bars develop a higher bond strength relative to tensile strength. This was expected, as smaller bars have a higher ratio of perimeter to cross sectional area than larger diameter bars. Finally they used the higher strength epoxy in tests where the epoxy was reinforced with 0.12 inch long glass fibers at a volume fraction of 5%. This was found to significantly enhance the strength of the bond and allowed close to full strength development of the inch dia. bars in 7.3 inches (less than half a concrete masonry unit length). This was the adhesive mixture used for the bending tests. The bending tests of eight specimens four narrow and four wide found a mean span to deflection ratio of 42. The authors felt that full anchorage of the FRP bars was assured with their methods and that the use of ACI 530-02 equations can be used to calculate the ultimate flexural strength design of concrete masonry beams and walls reinforced with nearsurface mounted FRP bars. Thanasis C. Triantafillou (1998) Composites: A New Possibility for the Shear Strengthening of Concrete, Masonry and Wood This paper reports research results related to the use of composites as shear strengthening materials for concrete, masonry and wood members. Presented are analytical models for the contribution of composites to the shear capacity of strengthened elements, within the framework of ultimate limit states. It is shown that in the case of concrete and masonry, the design of FRP strengthened members can be treated on the basis of the classical truss analogy and by

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42 accounting for an effective FRP strain, which depends on the product of the FRP elastic modulus and the area fraction. The total shear capacity, VRd, for a masonry wall of length l and thickness t reinforced with horizontal epoxy bonded FRP laminates with area fraction equal to h (defined as the total cross sectional area of laminates divided by the corresponding area of the wall) is given as: VRd = VRd1 + VRd2 < 0.3fktd /M fk characteristic compressive strength, masonry d = effective depth (taken approximately equal to 0.81 as suggested by Paulay and Priestly (1992) for masonry walls with several layers of reinforcement) M (not identified by Triantafillou but assumed to be a safety factor for masonry) taken as 2.5 by Triantafillou for calculations. VRd1 accounts primarily for the contribution of uncracked masonry VRd2 accounts for the effect of shear reinforcement modeled by truss anolgy VRd1 = fvktd /M fvk characteristic shear strength of masonry fvk = min [fvk0 + 0.4NRd/ lt 0.7fvk,lim, 0.7max(0.065fb, fvk0)] fvk0 characteristic shear strength of masonry under zero compressive stress. Is between 0.1 Mpa and 0.3Mpa (The lower limit applies in the absence of experimental data), depending on the type of masonry units and the mortar strength. fvk,lim = limiting value of fvk, is in the range of 1.0 MPa to 1.7 MPa, depending on the type of masonry units and the mortar strength.

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43 fb = normalized compressive strength of masonry units, is equal to a size factor factor (between 0.65 1.55) times the mean compressive strength of masonry units. Factor 0.7 applies only in the (usual) case of seismic design In simplified form: fvk = min (fvk0 + 0.4NRd/ lt fvk,max) VRd2 = hEfrp( rfrp,u/frp) t 0.9 d Efrp = Youngs modulus for FRP frp,u = ultimate tensile strain FRP frp = partial safety factor FRP r = reinforcement efficiency factor, depending on the exact FRP failure mechanism (FRP debonding or tensile fracture). Triantafillou has rewritten VRd2: VRd2 = 0.7/frp hEfrpfrp,elt frp,e = an effective FRP strain. Expected to decrease as hEfrp increases. Triantafillou gives the shear capacity of masonry strengthened with FRP laminates in final form as: VRd/ flt = (0.8/M)min(fvk0/fk + 0.4 NRd/fklt fvk,max/fk) + h (0.7/frp)(frp,e/M,u)0.25/M h = (M,uEfrp/fk)h frp,e = 0.0119 0.0205(hEfrp) + 0.0104(hEfrp)2 Triantifillou ignores the contribution of the vertical FRP to shear capacity, justified by assuming it only provides dowel action. He finally demonstrates with some typical values plugged into his equations that depending on the axial load, the increase in shear capacity due to the external

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44 reinforcement can be considerable, and that it reaches a cut-off value at relatively low values of h, corresponding to low values of FRP area laminates. O. S. Marshall and S. C. Sweeney (2002) In-Plane Shear Performance of Masonry Walls Strengthened With FRP Researchers conducted in-plane shear tests of 4 x 4 unreinforced double-wythe brick wall specimens and lightly reinforced single-wythe CMU wall specimens at the U.S. Army Engineer Research and Development Center Construction Engineering Research Laboratory. Both GFRP and CFRP laminates were tested. The laminates were applied to one wall face only. Conclusions: For low gravity loads (low rise buildings) it was discovered that the strength of the building was increased in relation to the amount of material that crossed the failure plane (typically the horizontal bed joint in low rise buildings). Strength increase was not linear with amount of FRP applied. For high gravity loads (typically medium rise buildings) the most common form of failure is rocking or X cracking. Multiple plies of FRP, particularly GFRP, do not always increase strength. Failure of this configuration was due to delamination of the FRP from the wall. The investigators felt this was an indication that the laminate was too stiff. FRP composites can be applied to increase the strength and change the failure mode of masonry walls in shear. In all cases, however, application of FRP laminate caused a shift to a less ductile failure mode. M. J. N. Priestly and F. Sieble, 1995 Design of Seismic Retrofit Measures For Concrete and Masonry Structures The authors report that seismic repair and retrofitting of structural walls can be accomplished very economically with thin advanced composite overlays. Tests focused on 1) reduction of shear deformations in seismically damaged structural walls, 2) repair or retrofitting of

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45 shear walls to achieve ductile flexural behaviour, 3) increase in flexural ductility of structural walls, 4) retrofitting of out -of-plane unreinforced structural walls. All tests were performed on full scale walls constructed of fully grouted hollow concrete masonry units. Subsequent to sandblasting and filling of voids with epoxy or polymer concrete, advanced composite overlays were applied to the wall surface either single or double-sided in the form of mats or woven fabrics saturated with resin in and impregnator. Especially for in-plane wall response, the authors felt that very thin overlays (one or two layers) can show significant seismic improvements. Forces to be transferred in the composite overlays are limited by the laminar shear or principal tensile strength of the existing structural wall material since the polymer resin typically has higher tensile capacities than concrete or masonry substrates. An overlay shear capacity, V0, is given as: V0 = f0tid f0 = allowable overlay stress based on a maximum allowable strain of 0.004 d = effective structural wall length t = thickness of composite overlay For typical wall aspect ratios (height approx. = length) the above strain criterion inherently assumes large shear deformations 0.4 % drift due to shear alone in order for the composite overlay to become effective. Additional limitations on the total allowable shear deformations can be imposed by reducing the allowable overlay stress level f0. Alternatively, stiffness criteria, rather than strength criteria, can be employed in the wall overlay design, limiting shear deformations to levels which can be expected in concrete

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46 walls with conventional horizontal reinforcement Ash (determined based on conventional concrete design requirements) by scaling the amount of horizontal overlay fabric Aoh from the required horizontal reinforcement as: Aoh = AshEs/ Eo which will also ensure equal participation of the already existing conventional horizontal wall reinforcement. The authors report on the testing of a full-scale five story reinforced building. This building was first tested under simulated seismic actions to failure. Subsequent to this testing it was repaired with structural carbon overlays up to the second story of the structural walls. The crushed wall toes were reconstructed with polymer concrete. The load-deflection envelopes for the original and the retest show that a single layer of carbon fabric (t = 1.25 mm, predominantly horizontal woven carbon fabric, 12 k toe AS4, with epoxy resin matrix), applied to each side of the strucural walls with two layers in the toe regions, contributed significantly to doubling the inelastic deformation capacity. Measured shear deformations in the repaired wall panels were reduced to half the shear deformations in the original test. Chadchart Sittipunt, Sharon L. Wood, Panitan Lukkunaprasit, and Pichai Pattararattanakul (2001) Cyclic Behavior of Reinforced Concrete Structural Walls with Diagonal Web Reinforcement These researchers reported that results from previous investigations2,3,4,5 demonstrated that structural walls that deform primarily in shear, and that experience large shear distortions, have a lower energy dissipation capacity than walls that deform primarily in flexure. In addition, it was found that walls that experience large shear distortions were more likely to fail by web crushing, which is caused by deterioration of the compressive strength of the concrete struts in the web2.

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47 Experimental results3,4 indicated that increasing the amount of conventional vertical and/or horizontal web reinforcement in walls th at were susceptible to shear failure did not significantly reduce the inelastic shear distortion nor did it appreciably improve the energy dissipation capacity. Subsequent analytical studies6,7 indicated that the hysteretic response of walls susceptible to shear failures could be improved if diagonal reinforcement was used in the web. Diagonal web reinforcement provided a more effective mechanism for transferring lateral forces into the foundation, resulting in lower shear strains near the base of the wall, and improving the energy dissipation characteristics. This paper also reported the results of four reinforced concrete wall tests. The purpose of the testing was to evaluate the influence of daigonal web reinforcement on the hysteretic response. Two walls contained conventional horizontal and vertical web reinforcement and two walls contained inclined web reinforcement. Within each type the total amount of reinforcement was varied. Reinforcement details were representative of construction practice in regions of low to moderate seismic risk. A single layer of web reinforcement was used. The walls were dumbbell shaped (plan view) with the edges (the bells) all containing the same reinforcement. They were held down at the base and load was applied in plane to an integral concrete cap with the walls behaving as cantilevers. Each wall was tested until it experienced significant loss of capacity. The walls with diagonal web reinforcement resisted higher loads than the other two, however, the increase in strength was not significant for the walls with higher web reinforcement ratios.

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48 Conclusions: Walls with diagonal web reinforcement displayed the ability to dissipate more energy at a given level of lateral deformation than walls with conventional web reinforcement. Increasing the amount of diagonal web reinforcement increased the energy dissipation capacity of the walls, whereas increasing the amount of conventional web reinforcement did not change the energy dissipation capacity of the walls significantly. Walls with diagonal web reinforcement experienced less shear distortion in the hinging region than walls with conventional web reinforcement. Shear deformation did increase, however, after the diagonal web reinforcement yielded. Web crushing was not observed in walls with diagonal web reinforcement. Analytical results indicated that part of the shear force was transferred directly to the foundation by the diagonal reinforcement. Diagonal web reinforcement also helped reduce inelastic shear deformation in the lower portion of the walls thereby preventing deterioration of the concrete strength in the compression struts. The decrease in force in the concrete struts and the decrease in inelastic shear deformation improves the shear transfer capacity of concrete in the web and prevents web crushing. Increasing the amount of conventional web reinforcement did not significantly reduce the shear deformation in the hinging regions, nor did it change the failure mechanism. Web crushing controlled the response of both walls that contained conventional web reinforcement. In walls with conventional web reinforcement, lateral force was transferred to the foundation by compression in concrete struts and dowel action in the reinforcement. Compressive strength of concrete struts deteriorated significantly when the walls were subjected to large inelastic shear distortions. Large shear forces in the compressive struts and deterioration of compressive strength led to crushing of the concrete in the web. REFERENCES 1. Paulay, T. and Priestly, M. J. N., Seismic Design of Reinforced Concrete and Masonry Buildings. John Wiley and Sons, Inc., New York, 1992. 2. Oesterle, R. G., Aristizabal-Ochoa, J. D., Shiu, K. N. and Corley, W. G. Web Crushing of Reinforced Concrete Walls. ACI Journal, May-June, 1984. 3. Oesterle, R. G., Fiorato, A. E., Johal, L. S., Carpenter, J. E., Russel, H. G. and Corley, W. G. Earthquake Resistant Structural Walls Tests of Isolated Walls. Report to National Science Foundation, Oct. 1976 4. Oesterle, R. G., Aristizabal-Ochoa, J. D ., Fiorato, A. E., Russel, H. G. and Corley, W. G. Earthquake Resistant Structural Walls Tests of Isolated Walls, Phase II. National Science Foundation, Oct., 1979.

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49 5. Oesterle, R. G., Inelastic Analysis for In-Plane Strength of Reinforced Concrete Shearwalls. PhD dissertation, CE dept. Northwestern University, Evanston, Ill., June 1986. 6. Stittipunt, C., and Wood, S. L., Finite Element Analysis of Reinforced Concrete Shearwalls. Civil Engineering Studies: Structural Research Series No. 584, University of Illinois, Urbana, Ill., Dec. 1993. 7. Stittipunt, C., and Wood, S. L., Influence of Web Reinforcement on the Cyclic Response of Structural Walls, ACI Structural Journal No.6, Nov.-Dec. 1995.

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50 APPENDIX B SPECIMEN CONSTRUCTION A local mason contractor was hired to build the wall specimens. Bricks used were grade MW 8 inch clay bricks purchased locally from Florida Rock Industries Inc located in Gainesville FL. The mortar used was type N. Eight test walls were built in a configuration simulating the pier of a wall located between two windows (Figure 34). Base Pier Figure 34: Illustration of specimen model This model was chosen because of the susceptibility of this portion of a structure to fail during an earthquake. The height of the pier is configured to be half of what it would be in a building. This is to simulate the node of a real pier. This is where the moment due to S bending, for a shear wall loaded due to an upper floor moving horizontal relative to the lower floor, is zero. Precast concrete lintels were used as a base for each wall after being filled with ready mixed concrete and reinforced longitudinally with two no. 6 steel reinforcing bars. Two holes were drilled in the lintels and tubes installed prior to the concrete pour. These were used as lifting points for each specimen.

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51 The length of the base lintels was 112 inches (2.84 m). They were used with the precast face up to provide a flat surface for laying the bricks. Figure 35 and Figure 36 illustrate the specimen configurations. 64 in. 48 in. 48 in. pier 16 in. base 112 in. (2.8m) Lifting holes Precast concrete lintel Precast concrete lintel (1.6 m) (1.2 m) (1.2 m) (0.4 m) Figure 35: Specimens II VIII Tests 1h, 1i, 2, 4, 5, 6, 7, 8 48 in. 48 in. pier 16 in. base 112 in. Lifting holes Pre-cast concrete lintel Pre-cast concrete lintel 64 in. (1.6 m) (1.2 m) (1.2 m) (0.4 m) (2.84 m) Figure 36: Specimen I Test 9

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52 Figure 37 shows the first course of brick being laid on the base lintel. A B Figure 37: A Base lintel, B First course of brick being laid The specimens were constructed in running bond with two wythes. Header courses were located at the fourth course up from the lintel and every sixth course after that. Collar joints were filled solid with mortar. Figure 38 A and B shows the typical brick and grout set-up for the base. A B Figure 38: A Brick laying and B grouting The wall base was laid six bricks tall (16 inches). The pier was centered on this base and built 48 inches wide and 48 inches tall. Specimen I (test 9) was constructed with mortar joints such that the top course of its base (sixth layer of bricks) had joints in line with the edges of the pier. On all other specimens the joints in the top course of the base were offset from the edges of the pier.

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53 Figure 39 A and B shows the bricks of a pier being laid. Figure 40 shows a header course being laid and Figure 41 shows a completed wall sans top lintel. A B Figure 39: A and B Laying pier bricks Figure 40: Laying header course Figure 41: Completed specimen (no top lintel)

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54 A second pre-cast concrete lintel was placed on top of the pier. This lintel was 64 inches long (5 feet, 4 inches) and was used for attaching the concrete cap of the test fixture. The walls were allowed to cure for 28 days before any GFRP was applied or any testing performed. From that time on GFRP and steel rebar (if used) were installed on one or two specimens at a time. The prepared specimens were tested prior to determining the GFRP/rebar configuration for the following specimens. The location and placement of the GFRP reinforcement was chosen to provide strengthening to areas that were susceptible to failure prior to the wall reaching a load that would yield the steel dowels or the tension straps/glass rebar. The GFRP placed in an X across the pier was used to prevent failure due to shear. The vertical straps along the edges of the pier were used to carry the tension load down through the brick to the pier/base interface or down through the base for specimens with no steel. GFRP was laid over the base to prevent bending failure there and across the top lintel/pier interface to prevent sliding of the lintel. The surfaces that FRP were to be applied to were wire brushed with a heavy duty motorized rotary wire brush. After testing the first specimen it was thought that FRP adhesion could be improved by sandblasting the brick surface. The rest of the specimens were sandblasted and the dust removed prior to the application of the FRP. Bond tests were later performed however and the brick substrate failed without exception whether the surface was wire brushed or sandblasted. SikaWrap Hex 100G was used as the glass fiber for specimens I, II, III, V, VII, and VIII. This is a unidirectional E-glass fiber. Weight is 27 oz. per sq. yd. This material

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55 was applied in various widths for in-plane stre ngthening of the pier as the vertical straps, reinforcement for diagonal tension strengthening as the X bracing, and flexural strengthening of the base as a strap applied along the top. A lighter weight glass fabric with strands oriented 45 degrees in two directions was applied as a full sheet to the base for shear strengthening and a strip across the joint between the bricks and the top lintel to strengthen the bond between these two elements. Both of these cloths were bonded to the walls using Sikadur 330, a high modulus two part epoxy. This resin was applied to the wall with a paint roller. The glass was then applied and more resin rolled onto the fabric until it was saturated or the glass was saturated first and then applied. Excess resin and air bubbles were forced out with a squeegee. A photo of this process is shown in Figure 42. Specimen IV used a pre-impregnated gla ss cloth. This was G 15000 unidirectional grid reinforcement from Clark Schwebel Tech-Fab Co. This material is made by bonding E-glass fiber rovings with epoxy resin in a c ontrolled factory environment. The adhesive for this wall was a low modulus two part trowleable epoxy from Thermal Chem. Specimen VI had no cloth. All reinforcement was no.3 fiberglass rebar Aslan 100 GFRP. Four vertical bars were installed the full height of the wall, two at each edge of the pier. Both bars of each pair were installed in a x inch groove four inches from each edge of the wall. X bracing was installed across the pier with a bar in each of similar grooves as well as another bar the length of the base across the top. The grooves were cut with a circular saw with a masonry blade and were slightly deepened as necessary to allow bars to cross each other. The bars were glued in with Concresive 1420.

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56 Figure 42: Applying FRP to a concrete block wall The steel rebar, when used, was glued into a inch diameter hole using Concresive 1420, a two part structural epoxy. The holes were drilled with a hammer drill starting at the top of the 12th brick course on one side and drilling diagonally downward to emerge at the bottom of the first course of bricks on the other side of the wall. The holes were brushed out and then blown out with the lab shop air to remove most of the dust. The holes were filled with epoxy using a length of tube inserted to the bottom. The tube was withdrawn as the glue was injected. The rebar was coated with epoxy as it was inserted into the hole. Figure 43 shows the epoxy injection system and Figure 44 A and B shows the process of injecting the epoxy into a rebar hole. Figure 43: Epoxy injection system

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57 A B Figure 44: A and B Injecting epoxy into rebar hole Figure 45 shows an edge view of the position of an installed steel rebar. This was typical for all specimens with steel added. All rebar was installed from the same side of the wall. No. 3 rebar Figure 45: Typical steel rebar configuration

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58 APPENDIX C EXPERIMENTAL PROGRAM Test Setup The test setup was designed to load the masonry specimens in plane (Figure 46). The inverted T configuration, representing the lower half of a wall pier between two windows, required tie-down points at each end. A 55 kip MTS hydraulic acutuator was placed between the top of the cap and the reaction frame. This actuator was part of a closed-loop hydraulic loading system. The system was controlled by an MTS 407 controller. The controller used a sinusoidal voltage output from the data acquisition system to impart the desired displacements to the cylinder. The actuator has a built-in load cell that was used to acquire the load imposed on the specimens during testing. Extension and retraction of this device simulated the loading conditions that would be experienced by a shear wall during ground movement parallel to the wall. The ICBO Acceptance Criteria for Concrete and Reinforced and Unreinforced Masonry Strengthening Using Fiber-Reinfor ced Composite Systems (ACI125) (ICBO 1997) was followed to determine the displacements to be imposed for each test. For walls with no steel the yield point was taken as the displacement that was expected to cause failure of an unreinforced wall. For walls with steel reinforcement yield was taken as the displacement at which the steel was expected to yield. These yield displacements were assigned = 1. The displacements then imposed during testing were fractions or multiples of = , 1, 2, 3, 4, 6, 8, 10, 12, 16 etc. The specimens were loaded in

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59 displacement control with three complete cycles for each displacement level A complete cycle was one displacement in each of the positive and negative directions. The specimens were loaded through increasing until lateral load carrying capacity was lost. 4 KIP/IN SPRING (QTY 2) STRONG FLOOR (THICK REINFORCED CONCRETE SLAB) 50 KIP HYDRAULIC ACTUATOR REACTION FRAME ALL THREAD ROD ALL THREAD ROD East West 2000 # CAP CONCRETE BASE Figure 46: Test stand North elevation Lateral movement out of plane of the top of the wall was prevented at the cap by attaching a strut at each end of the cap to a frame attached to the wall of the lab (Figure 47). These struts were pinned at the ends allowing free movement in plane of the wall. The base was a solid concrete block with longitudinal and stirrup steel reinforcement. It was first attached to the lab floor through two cast in place holes using three inch diameter studs threaded into sockets in the strong floor. The nuts to the studs which held the base down were tightened as much as possible by hand with a three foot long wrench.

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60 2 STRUTS (ONE EACH END OF CAP) SouthNort h Figure 47: Test stand East elevation The specimens were lifted and moved using bridge cranes connected to a handling fixture (see photo). This fixture consisted of a strongback, four vertical rods of Allthread, and four angle brackets. The brackets were bolted through the bottom lintel. The four rods were attached to the brackets and to the strongback, which was set on the top lintel. This allowed tightening of the rods, providing some compression to the wall during handling. The bridge crane was hooked to the strongback with a two legged sling. A inch high damn was built around the top edge of the base. Prior to setting each specimen in place a layer of Hydrostone was poured onto the base. The wall was then set into the wet Hydrostone. The lower section of the specimen was clamped down to the base with the use of a hydraulic jack. Small beams were used to transfer the force inboard from the location of the holdown brackets on the base. The jack applied tension to the hold down rods by pressing against the beams. A nut was tightened against the beam at the desired pressure on the jack and the jack was removed from the system. The beams imparted the force

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61 into steel plates set on the wall approximately 8 inches from the ends of the wall. The hold down force at each end was approximately 20,000 pounds. The cap is solid concrete with longitudinal and stirrup steel reinforcement. Four hollow tubes were installed longitudinally. These tubes were set at the bolt pattern of the clevis of the hydraulic ram allowing the ram to be attached to the cap with four threaded rods running through the cap which were nutted at the far end. A layer of mortar was placed on the top of the upper lintel and the cap was set on the wet grout with the two side struts and the hydraulic ram being attached just prior to the cap contacting the wall. The cap was then clamped to the lintel with threaded rod through cross beams. The nuts to the threaded rod were tightened as much as possible by hand using a three foot long pipe on the end of the wrench. A dial gauge was installed between the cap and the top lintel to indicate any relative movement between the two. None was detected during any of the tests. Two springs (4 kips/in. stiffness) were used to maintain a near constant vertical force on the specimen during in-plane testing. The springs were placed on a horizontal beam that rested on the cap. A second horizontal beam was placed on top of the springs. Two threaded rods passed through the beams and were connected to the concrete base below the specimen. The springs were compressed inches with a hydraulic jack and nuts on the rods were tightened to hold the spring force and transfer it into the specimen. The hydraulic pressure was released after the nuts were tightened. The springs imparted a downward force of 6000 pounds into the specimen. Combined with the 2000 lb. weight of the cap and the weight of the pier/lintel this provided a gravity load of 9000 pounds.

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62 With the geometry of the gravity load setup a horizontal displacement of one inch in either direction compressed the springs 0.005 inches. This adds 40 pounds of spring force. This does not account for spring compression due to rocking. The springs being located in the center of the wall would experience approximately half of the uplift expressed by Flo or Gina. This uplift typically turned out to be approximately equal to the horizontal displacement so for a inch horizontal movement the springs would recieve a inch compression. This would equate to an added vertical downward force of 2000 pounds. Figure 48 through Figure 53 show photos of the test fixture and specimen set-up. Figure 48: Specimen installed in test stand Figure 49: Reaction frame

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63 Figure 50: Lateral movement prevention struts Figure 51: Wall end of a lateral movement prevention strut

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64 Figure 52: One of two 'gravity' load springs Figure 53: Specimen handling fixture Instrumentation Figure 54 shows the location of either the instrument itself or the attachment point to the wall for the instrumentation that was common to all specimens. The type of each device shown is listed in Table 8 along with what measurement was being taken. Each device was either mounted to the wall with its probe contacting or attached to a solid stand or the device was mounted to a stand with its probe contacting or attached to the wall. The figure does not necessarily show the location of the instrument but the location where the measurement is being taken. All stands were heavy and solid to the lab floor. Carol and Diane were located as shown for several tests and then moved to the west side (same relative location) for the remainder of the tests.

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65 Carol Flo (oop) Will Diane Emily Karl Jim Henry Ian Vanessa (oop) GinaEast West (oop = out of plane) Figure 54: Instrumentat locations (string and linear pots) all walls Table 8: Instrumentation description Name Type Measurement Shown Carol String pot Horizontal Displacement in plane Attach point Gina String pot Vertical Displacement in plane Attach point Flo String pot Vertical Displacement in plane Attach point Emily Linear pot Horizontal Displacement in plane Instrument Diane String pot Horizontal Displacement in plane Attach point Will Linear pot Horizontal Displ acement out of plane Contact point Vanessa Linear pot Horizontal Displ acement out of plane Contact point Ian Linear pot Vertical Displacement in plane Instrument Henry Linear pot Vertical Displacement in plane Instrument Karl Linear pot Vertical Displacement in plane Instrument Jim Linear pot Vertical Displacement in plane Instrument Linda Strain Gauge Vertical strain FRP or glass rebar Nancy Strain Gauge Horizontal strain FRP or glass rebar Marie Strain Gauge Vertical strain FRP or glass rebar Oscar Strain Gauge Steel strain Pete Strain Gauge Steel strain Quin Strain Gauge Steel strain Rick Strain Gauge Steel strain

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66 Carol, Diane, Flo, and Gina were stri ng potentiometers (BEI Duncan miniature spring return linear motion sensors models 9610 and 9615). The string was pulled out to the approximate halfway point before being secured to allow for positive and negative measurements. The calibration factors were taken from the value imprinted on each instrument. The data acquisition program measured the potentiometer supply voltage as well as the output of the potentiometer so that and accurate linear measurement could be computed. The remainder of the potentiometers were calibrated using a calibration tool and a LabVIEW developed by the researchers. The tool held the instrument while the stroke length was measured and recorded by the LabVIEW program. The values recorded from this process were used to calculate the calibration factor. These pots were compressed to the approximate halfway point before being secured. This allowed positive and negative displacement readings to be taken. The FRP strain gauges (Texas Measurements Inc. Part no. PFL-30-11) were used to measure fiberglass strain in the sheet FRP in the configurations shown in Figure 55 Figure 59 and to measure glass rebar strain for test 8 Figure 58. When used with FRP sheet they were installed in the wet resin. When used with glass rebar they were glued to the rebar. The steel strain gauges (Texas Measurements Inc. Part no. FLA-5-11-1L) were glued to the rebar before the rebar was placed in the wall and located in the center of the bar in order to measure the strain at the pier/base interface. The locations of these gauges are shown in Figure 56, Figure 57, Figure 59, and Figure 60. These gauges were covered with tape and shrink wrap tubing for a length of four inches (Figure 61). This gave a four

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67 inch unbonded length of the steel to the brick allowing the steel strain to be distributed over this four inch length. Linda Nancy Marie (1h, 1i, 6 only) Figure 55: FRP strain gauge location Tests 1h, 1i, 5, 6 Oscar Pete Rick Quin Linda Nancy Figure 56: FRP and steel strain gauge locations Test 4 Oscar Pete Linda Figure 57: FRP and steel strain gauge locations Test 7

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68 Linda Marie N ancy Figure 58: Glass rebar strain gauge locations Test 8 Linda Oscar Pete Figure 59: FRP and steel strain gauge locations Test 9 Oscar Pete Figure 60: Steel strain gauge location Test 2

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69 Figure 61: Steel strain gauge installation Data Acquisition A personal computer, National Instruments LabVIEW software, and a 16-bit data acquisition card were used for acquiring the data. A LabVIEW program was developed to obtain and log the measurements. On the main screen (Figure 62), the user could specify file names for recording the data, identify cycle number, monitor the strain gauges and view a load vs. displacement graph for the test. The load and displacement shown on the screen are from the actuator load cell and Linearly Variable Displacement Transducer (LVDT). At the beginning of every test a Zero Scan was run before any specimen displacement occurred. The Zero Scan measured the initial positions of each of the instruments. A Regular Scan was run while the specimen was being displaced. The Regular Scan recorded the value of the current position of an instrument minus its value obtained from the Zero Scan. The Regular Scan value was shown on the screen.

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70 Figure 62: LabVIEW program main screen The MTS actuator was controlled by a program written in LabVIEW also (Figure 63). Input consisted of desired displacement value, frequency, and the number of cycles to run each displacement value. The program sent a voltage output, which corresponded to the to the particular displacement, to the MTS actuator. A calibration factor of 0.5 inches per volt output remained constant throughout the testing program. Figure 63: MTS Signal Generation program screen

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71 Component Tests Individual bricks, brick prisms, steel rebars, FRP tensile coupons, and FRP bond samples were tested to determine the compressive strength of the bricks and prisms, the tensile strength of the steel rebar and FRP samples, and the peel strength of the FRP bond to brick. Seven bricks were randomly taken from the pallet of bricks the walls were built from. These were tested in compression to failure in a Tinius Olsen testing machine. As each wall was being built a prism was constructed of four bricks using mortar from the batch being used for that wall. These were also tested in compression to failure in a Tinius Olsen machine. Four pieces of steel rebar were chosen randomly and tested in tension in the Tinius Olsen machine. ASTM A370 was followed for these tests. A sheet of the Hex 100G glass cloth was saturated with the Sikadur resin and allowed to cure. Five coupons were cut from this composite. These were cut to a length of 14 inches and milled to an average width of 1.04 inches. Two inch long grab tabs of printed circuit board fiberglass were epoxied to both sides of each end of these coupons for a gauge length of 10 inches. These pieces averaged 0.091 inches in thickness. These were tested in tension in the Tinius Olsen. The base of a tested wall was prepared for FRP bond strength tests. This involved using the glass that was already on the base of a sandblasted wall and applying some glass to a bare section that had been wire brushed. A coring saw was used to cut 2 inch diameter test patches by just cutting through the fiberglass to the brick surface. 2 inch diameter steel pucks were epoxied to these patches. After allowing everything to cure these pucks were pulled off the wall using a James Co. bond testing device which

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72 measured the force required to pull off the fiberglass patch. In all cases the brick substrate failed, indicated by the entire patch being covered with brick material. Material Properties Table 9 Table 14provide the results from the component tests. Table 9: Individual bricks Compressive strength Individual Bricks Test Compressive Stress (psi) 1 5610 2 5035 3 8635 4 8874 5 8203 6 9249 7 8891 Average 7785 Table 10: Brick prisms Compressive strength Brick Prisms Specimen Compressive Stress (psi) I 4210 II 3133 III 4479 IV no results V 3837 VI 4841 VII 4173 VIII 4925 Average 4228

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73 Table 11: Steel rebar Tensile strength No. 3 Steel Rebar Test Yield St ress (ksi) Elongation (%) 1 61 1.164 2 61 1.164 3 63 1.173 4 63 1.140 Average 62 1.160 Table 12: Glass rebar Tensile strength FRP Tensile Coupons Test kips /inch width Stress (ksi) 1 2.80 34.2 2 3.12 32.5 3 2.53 27.0 4 2.84 32.7 2.57 26.8 Average 2.77 30.64 Table 13: FRP bond tests Wire brushed wall FRP Bond Tests Wire Brushed Wall Test Force (lbs.) Stress (psi) 1 2250 716 2 1425 453 3 2800 891 4 2400 764 Average 2219 706 Table 14: FRP bond tests Sand blasted wall FRP Bond Tests Sand Blasted Wall Test Force (lbs.) Stress (psi) 1 2600 828 2 2750 875 3 2200 700 Average 2516 801

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74 The James Bond tester applies the force perpendicular to the surface of the FRP and pulls uniformly over the surface of the patch. The above results indicate the tensile properties of the brick. All that can be deduced about the bond strength of the FRP to brick perpendicular to the plane of the FRP is that it is stronger than the tensile capacity of brick. Of course this is all that is necessary for an application such as wall rehabilitation. These bond strengths were not seen for every wall tested. When separation of the FRP from the brick occurred without brick failure it is assumed that this was due to a peeling action (pulling from an edge), which is going to be a different strength than that tested by the James Bond tester. An admittedly non-scientific test was performed where several strips of the glass cloth were stuck to brick surfaces that were either wire brushed or sand blasted. Resin was applied and the strip bonded to the brick only for a two inch length leaving a handle. These strips were pulled from the brick surfaces by hand in a peeling action. The bond to the sand blasted surfaces was noticeably stronger than the bond to the wire brushed surfaces although no numbers for this bond strength were measured. Aslan 100 GFRP rebar This material was not tested as a component. The strength given by company literature for a no. 3 bar is 110 ksi. With a cross sectional area of 0.131 sq. inches this gives a tensile strength of 14.41 kips for a bar of this size. Pre-impregnated FRP This material was not tested but is specified as having a tensile strength of 1.2 kips per inch width of fabric.

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75 APPENDIX D SPECIMEN DETAILS AND RESULTS Brick test 1h Specimen ID: III Date of Testing: August 21, 2002 Date of Construction: 5/2/02 Date of FRP Application : 7/29/02 Conditions during FRP Application: Temp: 90F RH: 60% Conditions during Testing : Temp: 80F RH: 78% Material Properties : FRP Test Coupons tensile strength: Results (avg.) 30.64 ksi 2.77 kips/inch width FRP/Resin Pulloff tests Results: Brick failure, 700 psi to 890 psi Brick Prisms Results (avg.) 4.23 ksi Brick Results (avg.) 7.79 ksi Failure Mode : Pier Rocking

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76 Description of Failure : Vertical FRP peeled away from the brick at Pier/Base interface, debond progressing from interface and moving up incrementally with each displacement cycle. The bond of the FRP to brick was inadequate to allow tensile reinforcement failure across the pier/base interface. Debonding probably occurred due to out of plane movement of wall. Table 15 and Figure 64 and Figure 65 describe and show the location of the FRP. Table 15: FRP description test 1h Description of FRP Reinforcement Test 1h Specimen III ID Direction Area (in.2) Width (in.) Length (in.) A Unidirectional .042 3 68 B Unidirectional .084 6 112 C +45 deg 18 112 D Unidirectional .042 3 68 E +45 deg 12 48 Resin Sikadur Hex 300. Glass SikaWrap Hex 100G B C Figure 64: FRP layup North side E D A B C (2 PL) Figure 65: FRP layup South side

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77 Table 15 and Figure 66 show crack circumstances and locations. Table 16: Crack occurrence Crack Occurrence Test 1h Location Span Ram LVDT (in.) 1 0.17 3 2 0.23 4 1 2 2 Figure 66: Crack pattern at failure Figure 67 and Figure 68 show photos of specimen 1h. Figure 67: A North side. B South side

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78 Figure 68: Progression of glass debonding (black lines) Figure 69 shows plots of the data for specimen 1h. -20 -10 0 10 20 -2-1012 DisplacementLoad (kips) -20 -10 0 10 20 -2-1012 Drift (%)Load (kips)-89 -44.5 0 44.5 89Load (kN) -5000 -2500 0 2500 5000 -11 Displacement (in.)FRP Strain N (uE) 0 20000 40000 -11 Displacement (in.)FRP Strain L (uE)

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79 -20000 -10000 0 10000 20000 -101 Displacement (in.)FRP Strain M (uE) Displacement (in.) -1 -0.5 0 0.5 1 -1-0.500.51Out of Plane W (in.) Displacement (in.) -1 -0.5 0 0.5 1 -1-0.500.51Out of Plane V (in.) -0.3 -0.2 -0.1 0.1 -0.50.00.5 DisplacementJim -0.3 -0.2 -0.1 0.1 -0.50.5 DisplacementIan -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 -0.50.00.5 DisplacementKarl -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 -0.50.5 DisplacementHenry Figure 69: Data reduction plots

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80 Brick test 1i Specimen ID: III Date of Testing: 8/23/02 Date of Construction: 5/2/02 Date of FRP Application : 8/22/02 Conditions during FRP Application: Temp: 90F RH: 60% Conditions during Testing : Temp: 80F RH: 78% Material Properties : FRP Test Coupons tensile strength: Results Not Applicable FRP/Resin Pulloff tests Results: Brick failure, 700 psi to 890 psi Brick Prisms Results 4.23 ksi Brick Results 7.79 ksi Failure Mode : Pier Rocking/FRP tensile failure at sill Description of Failure : Spray-on FRP began cracking at the pier/base interface on the east edge of the west strip Cracking began at 0.12 inches ram displacement. Cracking of FRP continued up the east edge of strip as displacement increased culminating in rupture across the strip approximately 12 inches above pier/base interface.

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81 Comments: Test specimen III was tested in test 1h. After completion of test 1h spray on chopped fiberglass was sprayed onto wall on the opposite side from the laid up vertical FRP. Each edge received a vertical strip of spray on FRP from bottom of base to top of pier, 4 inches in from edge. Dimensions: approx. 8 inches wide x approx. 5 mm thick measured at sill line. 2 inch fiber length. Vinyl Ester resin. Table 17 and Figure 70 show FRP description and location Table 17: FRP description Test 1i Description of FRP Reinforcement Test 1i Specimen III ID Direction Area (in.2) Width (in.) Length (in.) A Unidirectional .042 3 68 B Unidirectional .084 6 112 C +45 deg 18 112 D Unidirectional .042 3 68 E +45 deg 12 48 F random 2 in. fiber length sprayed on 1.6 8 64 Resin Vinyl Ester for spray-on. Sikadur Hex 300 for layed up. Glass 2 inch chopped for spray-on. SikaWrap Hex 100G for layed up. F C B E D A B C (2 PL) Figure 70: A Spray on/ FRP layup No rth side. B FRP layup South side

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82 Table 18 and Figure 71 show crack occurrence and location Table 18: Crack occurrence Test 1i Crack Occurrence Test 1i Crack in specimen occurred during te sting of specimen in test 1h. 1 2 2 Figure 71: Crack pattern at failure Figure 72 and Figure 73 show photos of test 1i. Figure 72: Overall view North side

PAGE 96

83 Figure 73: Tear in FRP Figure 74 shows the data reduction plots. -20 -15 -10 -5 0 5 10 15 20 -2-1012 Drift (%)Load (kips)-89 -44.5 0 44.5 89Load (kN) Displacement (in.) -1 -0.5 0 0.5 1 -1-0.500.51Out of Plane W (in.) -0.3 -0.2 -0.1 0.0 0.1 -101 Displacement (in.)Jim (in.) -0.3 -0.2 -0.1 0.0 0.1 -101 Displacement (in.)Ian (in.)

PAGE 97

84 -0.3 -0.2 -0.1 0.0 0.1 -101 Displacement (in.)Karl (in.) -0.3 -0.2 -0.1 0.0 0.1 -101 Displacement (in.)Henry (in.) Figure 74: Data reduction plots

PAGE 98

85 Brick test 2 Specimen ID: VIII Date of Testing: 12/03/02 Date of Construction: 5/28/02 Date of FRP Application : 11/14/02 Conditions during FRP Application: Temp: 67F RH: 58% Conditions during Testing : Temp: 73 deg. F RH: 50 % Material Properties : FRP Test Coupons tensile strength: Results 30.64 ksi 2.7 kips/inch width FRP/Resin Pulloff tests Results: Brick failure, 700 psi to 890 psi Brick Prisms Results 4.23 ksi Brick Results 7.79 ksi Failure Mode : Diagonal Tension, Pier Rocking. Description of Failure : Wall cracked diagonally above one rebar and vertically/slight diagonal next to the other one. It cracked across the base of the pier and across the wall at the top of the rebar. Some delamination of FRP occurred at base of pier. FRP that came loose had pieces of brick stuck to it. Sliding is indicated by the lower loops in the Load vs. Displacement and the plot of Diane vs. Displacement. First steel yield is indicated at the .064 displacement blip in the Load vs. Displacement and is confirmed by the enlargement of the Steel Strain Pete plot. Steel stretched and took a lot of set as shown on Steel Strain Oscar.

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86 Table 19 and Figure 75 show FRP description and layup Table 19: FRP description test 2 Description of FRP Reinforcement Test 2 Specimen VIII ID Direction Area (in.2) Width (in.) Length (in.) A Unidirectional .028 2 48 B Unidirectional .084 6 112 C +45 deg 18 112 D Unidirectional .042 3 68 E +45 deg 12 48 Resin supplied by Sika EA B C (2 PL) N O. 3 REBAR (2 PL) E D A B C (2 PL) Figure 75: A FRP layup North side. B FRP layup South side

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87 Table 20 and Figure 76 show crack occurrence and location. Table 20: Crack occurrence Test 2 Crack Occurrence Test 2 LocationSpan Ram LVDT (in.) 1 0.064 1 2 0.128 2 3 0.256 4 4 0.384 6 5 0.512 8 6 0.768 12 7 1.024 16 A 1 2 2 3 4 5 5 6 6 7 3 4 B 2 3 3 4 4 3 4 5 5 6 6 Figure 76: Crack pattern at failure A North side, B South side Figure 77 Figure 79 show photos of test 2.

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88 A B Figure 77: A Overall view North side. B view South side A B Figure 78: A East edge of pier. B South side crack pattern Figure 79: FRP pulloff North side

PAGE 102

89 Figure 80 shows the data reduction plots for test 2. -20 -10 0 10 20 -2-1012 Displacement (in.)Load (kips) -20 -10 0 10 20 -2-1012 Drift (%)Load (kips)-89 -44.5 0 44.5 89Load (kN) -1 -0.5 0 0.5 1 -1-0.500.51 Displacement (in.)Ou t of Plane V (in.) -1 -0.5 0 0.5 1 -1-0.500.51 Displacement (in.)Ou t of Plane W (in.) 0 2000 4000 6000 -101 Displacement (in)Steel Strain Pete (uE) -1000 0 1000 2000 3000 4000 5000 -101 Displacement (in)Steel Strain Oscar(uE) -0.1 0.0 0.1 0.2 0.3 -1.00.01.0 DisplacementDiane 0 2000 4000 6000 -0.100.00 Displacement (in)Steel Strain Pete (uE)` Figure 80: Data reduction plots test 2

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90 Brick test 4 Specimen ID: II Date of Testing: 12/18/02 Date of Construction: 5/30/02 Date of FRP Application : 11/14/02 Conditions during FRP Application: Temp: 67F RH: 52% Conditions during Testing : Temp: 73 deg. RH: 70% Material Properties : FRP Test Coupons tensile strength: Results: 30.64 ksi FRP/Resin Pulloff tests Results: Brick failure, 700 psi to 890 psi Brick Prisms Results: 4.23 ksi Brick Results: 7.79 ksi Failure Mode : Pier Rocking/Tensile failure of Brick/mortar. Description of Failure : Cracking started and progressed in the lower area of the pier through mortar joints and across bricks, confining itself to the area between the top of the rebar and the base of the pier. The brick st arts to break up around the outer rebars and the load redistributes and is picked up by the inner rebars. This is indicated by the slight flat spot in the positive quadrant of Load vs. Displacement and the drop of load in the negative quadrant. All bars indicate large yield displacements in the last cycle. The west edge of the pier broke away and walked its elf west as indicated by Diane and the large gap in the vertical crack. The west edge also ratcheted itself up at the pier/base interface as shown by Ian vs. Displacement.

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91 Table 21 and Figure 81 show FRP description and layup. Table 21: FRP description test 4 Description of FRP Reinforcement Test 4 Specimen II ID Direction Area (in.2) Width (in.) Length (in.) A Unidirectional .042 3 48 B Unidirectional .084 6 112 C +45 deg 18 112 D Unidirectional .042 3 68 E +45 deg 12 48 Resin supplied by Sika A E D A B C (2 PL) N O. 3 REBAR (4 PL) B EA (2 PL) C B Figure 81: FRP layup A North side, B South side Table 22 and Figure 82 show crack occurrence and location. Table 22: Crack occurrence Test 4 Crack Occurrence Test 4 LocationSpan Ram LVDT (in.) 1 0.085 1 2 0.169 2 3 0.254 3 4 0.338 4 5 0.507 6 6 0.68 8

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92 A 1 2 3 3 3 4 4 5 5 5 B 1 3 3 4 4 5 5 6 Figure 82: Crack pattern at failure A North side, B South side Figure 83 and Figure 84 show photos of test 4. A B Figure 83: A North side, B No rth side, east edge of pier A B Figure 84: A South side, east edge of pi er, B South side lower center of pier

PAGE 106

93 Figure 85 shows the data reduction plots for test 4. -20 -10 0 10 20 -2-1012 Displacement (in.)Load (kips) -20 -10 0 10 20 -2-1012 Drift (%)Load (kips)-89 -44.5 0 44.5 89Load (kN) -2500 0 2500 5000 -101Displacement (in.)FRP Strain N (uE) 0 5000 10000 15000 -101Displacement (in.)FRP Strain L (uE) -3000 0 3000 6000 -101Displacement (in.)Steel Strain R (uE) -3000 0 3000 6000 -101 Displacement (in.)Steel Strain Q (uE) -3000 0 3000 6000 -101Displacement (in.)Steel Strain O (uE) -3000 0 3000 6000 -101 Displacement (in.)Steel Strain P (uE) Displacement -1 -0.5 0 0.5 1 -1-0.500.51Out of Plane V (in.) Displacement -1 -0.5 0 0.5 1 -1-0.500.51Out of Plane W (in.)

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94 0.0 0.5 1.0 -0.6-0.4-0.20.00.20.40.6 DisplacementDiane -0.5 -0.4 -0.3 -0.2 -0.1 0.0 -0.6-0.4-0.20.00.20.40.6 DisplacementIan -0.01 0.00 0.01 0.02 -0.6-0.4-0.20.00.20.40.6 DisplacementHenry Figure 85: Data reduction plots Test 4

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95 Brick test 5 Specimen ID: V Date of Testing: 2/03/03 Date of Construction: 5/31/02 Date of FRP Application : 1/13/03 Conditions during FRP Application: Temp: 52F RH: 84% Conditions during Testing : Temp: 77 deg. RH: 55% Material Properties : FRP Test Coupons tensile strength: Results: 30.64 ksi FRP/Resin Pulloff tests Results: Brick failure, 700 psi to 890 psi Brick Prisms Results: 4.23 ksi Brick Results: 7.79 ksi Failure Mode : Pier rocking FRP rupture Description of Failure : Pier cracked and started coming apart between the top of the rebar and the pier/base interface. The vertical FRP at both edges delaminated starting at the pier/base interface and moving upward during the last cycle of loading and finally ruptured at pier/base at east end. FRP delaminated along with brick failure (pieces of brick torn from the wall by FRP) at west e nd. Rocking is indicated by Jim and Ian vs. Displacement.

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96 Table 23 and Figure 86 show FRP description and layup. Table 23: FRP description test 5 Description of FRP Reinforcement Test 5 Specimen V ID Direction Area (in.2) Width (in.) Length (in.) A Unidirectional .042 3 64 B Unidirectional .084 6 112 C +45 deg 18 112 D Unidirectional .042 3 68 Resin supplied by Sika D A B C (2 PL) Figure 86: FRP layup North side (No FRP on south side) Table 24 and Figure 87 and Figure 88 show crack occurrence and location. Table 24: Crack occurrence test 5 Crack Occurrence Test 5 LocationSpan Ram LVDT (in.) 1 0.152 3 2 0.203 4 3 0.305 6 4 0.406 8

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97 1 2 4 4 GLASS RUPTURE Figure 87: Crack pattern at failure North side (Glass rupture is vertical strip A, east) INSTL. CRACKS (2 PL) 2 3 Figure 88: Crack pattern at failure South side

PAGE 111

98 Figure 89 and Figure 90 show photos of test. A B Figure 89: A overall view, B West edge of pier A B Figure 90: A Glass break in vertical strip A east edge, B Delamination pattern

PAGE 112

99 Figure 91 shows the data reduction plots for test 5. -20 -10 0 10 20 -2-1012 Drift (%)Load (kips)-89 -44.5 0 44.5 89Load (kN) 0.0 50.0 100.0 150.0 -0.50.5Displacement (in.)FRP Strain N (uE) 0 10000 20000 30000 40000 -101Displacement (in.)FRP Strain L (uE) Displacement (in.) -1 -0.5 0 0.5 1 -1-0.500.51Out of Plane V (in.) Displacement (in.) -1 -0.5 0 0.5 1 -1-0.500.51Out of Plane W (in.) -0.35 -0.25 -0.15 -0.05 -0.50.5 DisplacementJim -0.35 -0.25 -0.15 -0.05 0.05 -0.50.5 DisplacementIan Figure 91: Data reduction plots Test 5

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100 Brick test 6 Specimen ID: IV Date of Testing: 2/12/03 Date of Construction: 6/1/02 Date of FRP Application : 1/23/03 Conditions during FRP Application: Temp: 53F RH: 78% Conditions during Testing : Temp: 73 deg. RH: 55% Material Properties : FRP Specifications: 1.2 kips per inch width FRP Test Coupons tensile strength: Results: Not applicable FRP/Resin Pulloff tests Results: Brick failure, 700 psi to 890 psi Brick Prisms Results: 4.23 ksi Brick Results: 7.79 ksi Failure Mode : Pier rocking mortar/brick tensile failure Description of Failure : Brick and mortar in the pier/base area failed through successive cracking on the side away from the FRP applied surface.

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101 Table 25 and Figure 92 show FRP description and layup for test 6. Table 25: FRP description Test 6 Description of FRP Reinforcement Test 6 Specimen IV ID Direction Area (in.2) Width (in.) Length (in.) A Unidirectional 0.042 6 1/2 68 B Unidirectional 0.07812 112 C Unidirectiona 0.12319 112 D Unidirectional 0.0457 68 Resin supplied by Thermal Chem B D A C (2 PL) Figure 92: FRP layup North side (No FRP on south side) Table 26 and Figure 93 show crack occurrence and location. Table 26: Crack occurrence test 6 Crack Occurrence Test 6 LocationSpan Ram LVDT (in.) 1 0.305 6 2 0.406 8 3 0.61 12 4 0.813 16 5 1.02 20 6 1.224 24 7 1.53 30

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102 A GLASS RUPTURE 3 3 3 6 6 B 1 1 2 3 3 3 4 3 4 4 5 5 6 6 6 7 7 7 7 7 Figure 93: Crack pattern at failure A North side, B South side ( glass rupture is A straps) Figure 94 and Figure 95 show photos of test 6. A B Figure 94: A Overall view North side, B South side Figure 95: North side after test

PAGE 116

103 Figure 96 shows the data reduction plots for test 6. -20 -10 0 10 20 -2-1012 Displacement (in.)Load (kips) -20 -10 0 10 20 -2-1012 Drift (%)Load (kips)-89 -44.5 0 44.5 89Load (kN) 0 2500 5000 -101Displacement (in.)FRP Strain N (uE) -5000 0 5000 10000 15000 -101 Displacement (in.)FRP Strain M (uE) -5000 0 5000 10000 -101Displacement (in.)FRP Pier Strain L (uE) Displacement (in.) -1 -0.5 0 0.5 1 -1-0.500.51Out of Plane V (in.) Displacement (in.) -1 -0.5 0 0.5 1 -1-0.500.51Out of Plane W (in.) Figure 96: Data reduction plots test 6

PAGE 117

104 Brick test 7 Specimen ID: VII Date of Testing: 3/24/03 Date of Construction: 5/29/02 Date of FRP Application : 3/20/03 Conditions during FRP Application: Temp: 84F RH: 71% Conditions during Testing : Temp: 77 deg. RH: 100% Material Properties : FRP Test Coupons tensile strength: Results: 30.64 ksi FRP/Resin Pulloff tests Results: Brick failure, 700 psi to 890 psi Brick Prisms Results: 4.23 ksi Brick Results: 7.79 ksi Failure Mode : Pier Rocking/Diagonal tension failure across mortar and bricks. Description of Failure: Cracking started in mortar at pier/base interface. During subsequent displacements the edges of the wall cracked at the mortar joints between the top of the rebar and the base with the cracks progressing across the wall. The west edge of the wall cracked diagonally from the top of the rebar and going down and from the pier/base going up, cracks occurring through joints and bricks. Vertical and X FRP started peeling from th e brick at the pier/base interface at 0.178 in. displacement and continued up the wall incrementally, however this was intermittently spaced and both vertical strips remained bonded to the brick at the lower ends until the last cycle at which both strips pulled from the wall, taking pieces of brick with them.

PAGE 118

105 This FRP failure is indicated at both wall edges by sharp changes in FRP Strain Linda in both quadrants at .603 and 0.7295 displacements. The west edge of the wall breaking away and moving west is indicated by the ratcheting shown on Diane vs. Displacement. The entire pier ratcheted itself up to a total of 0.1 inches as shown on Jim and Ian vs. Displacement. Table 27 and Figure 97 show FRP description and layup for test 7. Table 27: FRP description Test 7 Description of FRP Reinforcement Test 7 Specimen VII ID Direction Area (in.2) Width (in.) Length (in.) A Unidirectional .042 3 48 B Unidirectional .084 6 112 C +45 deg 18 112 D Unidirectional .042 3 68 E +45 deg 12 48 Resin supplied by Sika E D A B C (2 PL) #3 rebar (2 PL) Figure 97: FRP layup Test 7

PAGE 119

106 Table 28 and Figure 98 show crack occurrence and location. Table 28: Crack occurrence Test 7 Crack Occurrence Test 7 Location Span Ram LVDT (in.) 1 0.045 1 2 0.089 2 3 0.178 4 4 0.267 6 5 0.357 8 6 0.535 12 7 0.713 16 1 2 2 3 3 3 3 4 4 4 5 5 5 5 5 6 4 6 6 2 3 4 4 5 6 6 7 Figure 98: Crack pattern at failure A North side, B South side

PAGE 120

107 Figure 99, Figure 100 and Figure 101 show photos of test 7. A B Figure 99: A Overall view, B FRP delamination, east edge of pier A B Figure 100: A North side, west edge of pi er, B South side, west edge of pier A B Figure 101: A delamination North side, B south side

PAGE 121

108 Figure 102 shows the data reduction plots for test 7 -20 -10 0 10 20 -2-1012 Displacement (in.)Load (kips) -20 -10 0 10 20 -2-1012 Drift (%)Load (kips)-89 -44.5 0 44.5 89Load (kN) -1 -0.5 0 0.5 1 -1-0.500.51 Displacement (in.)Ou t of Plane V (in.) -1 -0.5 0 0.5 1 -1-0.500.51 Displacement (in.)Ou t of Plane W (in.) -2000 0 2000 4000 6000 8000 10000 12000 -101Displacement (in)FRP Strain L (uE) 0 1000 2000 0.00.51.0Displacement (in)FRP Strain L (uE) -0.5 0.0 -1.0-0.50.00.51.0 DisplacementJim -0.5 0.0 -1.0-0.50.00.51.0 DisplacementIan 0.0 0.1 0.2 -1.0-0.50.00.51.0 DisplacementDiane Figure 102: Data reduction plots test 7

PAGE 122

109 Brick test 8 Specimen ID: VI Date of Testing: 3/28/03 Date of Construction: 5/29/02 Date of FRP Application : 3/20/03 Conditions during FRP Application: Temp: 84F RH: 71% Conditions during Testing : Temp: 77 deg RH: 77% Material Properties : Glass rebar Tensile strength: Specifications 110 ksi Modulus of Elasticity: Specifications 5.92 x 106 psi FRP/Resin Pulloff tests Results: Brick failure, 700 psi to 890 psi Brick Prisms Results: 4.23 ksi Brick Results: 7.79 ksi Failure Mode : Mortar joint tensile failure in base. Description of Failure : The base failed in flexure. As the pier rocked on the base the fiberglass tendons that were in tension pulled up on the base while the compression side pushed down on the base, bending the base into an S. As cracking occurs it releases strain in the glass rebar. The steeper dropoff in strain indicated on the strain M diagram is due to the localized cracking occurring along the lower end of of the two rebars while the more gradual drop in strain shown on the strain L diagram is due to the cracking being dispersed across the base.

PAGE 123

110 The steep drop in load indicated in the negative quadrant of the Load diagram is due to the greater concentration of local cracking around the north rebars. This drop in strain for Marie causes Linda to pick up additional strain. This is shown in the magnified stain L diagram. The north side of the pier jumped up at this point and the base dropped down. These movements are shown on the magnified Ian and Henry diagrams. The positive glass strains shown on both M and L strain diagrams for positive and negative displacement are due to the fact that the vertical rebars are always on the tension side of the neutral axis. Table 29 and Figure 103 show FRP description and installation for test 8. Figure 104 shows section cut views of the glass rebar installation. Table 29: FRP descripton Test 8 Description of FRP Reinforcement Test 8 Specimen VI All FRP is # 3 Fiberglass rebar. Glass Rebar (7 PL) Figure 103: Glass rebar installation/location test 8 A 4 in. (2 PL) B 0.75 in.

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111 C 0.75 in. 1.25 in. 0.75 in. Figure 104: A Pier section glass rebar loca tion, B typical single bar inch groove, C Vertical bars inch groove. Horizontal bar crosses outside Table 30 and Figure 105 show the crack occurrence and location for test 8 Table 30: Crack occurrence Test 8 Crack Occurrence Test 8 LocationSpan Ram LVDT (in.) 1 0.069 1 2 0.207 3 3 0.275 4 4 0.413 6 5 0.551 8 6 0.688 10 7 0.826 12

PAGE 125

112 A INSTL. CRACK INSTL. CRACK 4 5 2 3 4 6 B INSTL. CRACK INSTL. CRACK 1 1 2 3 3 4 5 5 5 6 6 7 Figure 105: Crack pattern at failure A North side, B South side

PAGE 126

113 Figure 106 Figure 108 show photos of test 8. Figure 106: Overall view North side A B Figure 107: North side of base A east edge, B west edge A B Figure 108: South side of base A west edge, B east edge

PAGE 127

114 Figure 109 shows data reduction plots for test 8. -20 -10 0 10 20 -2-1012 Displacement (in.)Load (kips) -20 -10 0 10 20 -3-2-10123 Drift (%)Load (kips)-89 -44.5 0 44.5 89Load (kN) 0 2000 4000 6000 8000 -2-1012 Displacement (in.)glass rebar Strain N (uE) -2000 0 2000 4000 6000 8000 10000 12000 -2-1012 Displacement (in.)glass rebar Strain M (uE) -2000 0 2000 4000 6000 8000 10000 -2-1012 Displacement (in.)glass rebar Strain L (uE) 1000 2000 3000 -0.6-0.4 Displacement (in.)glass rebar Strain L (uE) Displacement (in.) -1 -0.5 0 0.5 1 -1-0.500.51Out of Plane W (in.) Displacement (in.) -1 -0.5 0 0.5 1 -1-0.500.51Out of Plane V (in.)

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115 -1.0 -0.5 0.0 -1.0-0.50.00.51.0 Displacement (in.)Jim (in.) -1.0 -0.5 0.0 -1.0-0.50.00.51.0 Displacement (in.)Ian (in.) -0.45 -0.35 -0.55-0.45 Displacement (in.)Ian (in.) -0.1 0.0 0.1 0.2 0.3 -1.0-0.50.00.51.0 Displacement (in.)Karl (in.) -0.1 0.0 0.1 0.2 0.3 -1.0-0.50.00.51.0 Displacement (in.)Henry (in.) 0.03 0.08 -0.52-0.47 Displacement (in.)Henry (in.) Figure 109: Data reduction plots Test 8

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116 Brick test 9 Specimen ID: I Date of Testing: 4/08/03 Date of Construction: 5/28/02 Date of FRP Application : 3/20/03 Conditions during FRP Application: Temp: 84F RH: 71% Conditions during Testing : Temp: 76 deg. F. RH: 81% Material Properties : FRP Test Coupons tensile strength: Results: 30.64 ksi FRP/Resin Pulloff tests Results: Brick failure, 700 psi to 890 psi Brick Prisms Results: 4.23 ksi Brick Results: 7.79 ksi Failure Mode : Mortar joint tensile failure in base. Description of Failure : The pier stayed together as a unit and exhibited no noticeable cracking. The rebar in tension for positive load (Oscar) exhibits a drop in strain at the same point the load drops off From there on for positive loading the base lifts up and rocks with the pier. This is demonstrated on the Karl vs. Displacement graph. The rebar may have just reached yield as the base started breaking up. For negative loading it appears that the tension rebar (Pete) was pulling out of the hole. This would be explained by the small amount of strain in Pete along with the small amount of uplifting of the base (Henry) while the pier uplift equals that of Jim.

PAGE 130

117 The pier and base both walked to the east as shown on Emily and Carol vs Displacement. Table 31 and Figure 110 show FRP description and layup for test 9. Table 31: FRP description Test 9 Description of FRP Reinforcement Test 9 Specimen I ID Direction Area (in.2) Width (in.) Length (in.) A Unidirectional .042 3 48 B Unidirectional .042 3 68 +45 deg 12 48 Resin supplied by Sika C B A (2 PL) #3 rebar (2 PL) Figure 110: FRP layup North side Test 9

PAGE 131

118 Table 32 and Figure 111 show the crack occurrence and location for test 9. Table 32: Crack occurrence Test 9 Crack Occurrence Test 9 LocationSpan Ram LVDT (in.) 1 0.048 1 2 0.096 2 3 0.145 3 4 0.193 4 5 0.289 6 6 0.386 8 7 0.675 14 A 1 2 3 3 3 3 5 5 5 6 7 B 2 2 3 3 4 4 5 5 6 7 7 Figure 111: Crack pattern at failure A North side, B South side

PAGE 132

119 Figure 112 and Figure 113 show photos of test 9. Figure 112: Overall view North side A B Figure 113: A South side, B North side

PAGE 133

120 Figure 114 shows the data reduction plots for test 9. -20 -10 0 10 20 -2-1012 Displacement (in.)Load (kips) -20 -10 0 10 20 -2-1012 Drift (%)Load (kips)-89 -44.5 0 44.5 89Load (kN) -20 0 20 40 60 80 100 120 -1.0-0.50.00.51.0 Displacement (in)FRP Strain L (uE) -1 -0.5 0 0.5 1 -1-0.500.51 Displacement (in.)Ou t of Plane V (in.) -1 -0.5 0 0.5 1 -1-0.500.51 Displacement (in.)Ou t of Plane W (in.) 0 3000 6000 -101Displacement (in)Steel Strain Pete (uE) 0 3000 6000 -101 Displacement (in)Steel Strain Oscar(uE)

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121 -0.5 0.0 0.5 -0.6-0.4-0.20.00.20.40.6 Displacement (in.)Jim (in.) -0.5 0.0 0.5 -0.6-0.4-0.20.00.20.40.6 Displacement (in.)Ian (in.) 0.00 0.10 0.20 -0.6-0.4-0.20.00.20.40.6 Displacement (in.)Karl (in.) -0.01 0.00 0.01 0.02 0.03 0.04 -0.6-0.4-0.20.00.20.40.6 Displacement (in.)Henry (in.) 0.00 0.03 -0.6-0.4-0.20.00.20.40.6 Displacement (in.) Emily (in.) -0.06 -0.03 0.00 0.03 -0.6-0.4-0.20.00.20.40.6 Displacement (in.)Diane (in.) -0.002 -0.001 0.001 0.002 0.003 -0.2-0.10.00.10.20.3 Displacement (in.) Emily (in.) Figure 114: Data reduction plots Test 9

PAGE 135

122 LIST OF REFERENCES Bajpai, K., and Duthinh, D. (ND) "Bending Performance of Masonry Walls Strengthened with Surface Mounted FRP Bars." Ninth North American Masonry Conference Clemson, SC. Council, A. T. (1997a). "Commentary on the NEHRP Guidelines for the Seismic Rehabilitation of Buildings (FEMA Publication 273)." Federal Emergency Management Agency, Washington, D.C. Council, A. T. (1997b). "NEHRP Guidelines for the Seismic Rehabilitation of Buildings (FEMA Publication 273)." Federal Emergency Management Agency, Washington, D.C. Ehsani, M. R., Saadatmanesh, H., and Velazquez-Dimas, J. I. (1999). "Behavior of retrofitted URM walls under simulated earthquake loading." Journal of Composites for Construction 3(3), 134-142. Holberg, A. M., and Hamilton Iii, H. R. (2002). "Strengthening URM with GFRP composites and ductile connections." Earthquake Spectra 18(1), 63-84. Marshall, O. S., and Sweeney, S. C. (2002). "In-plane shear performance of masonry walls strengthened with FRP." International SAMPE Symposium and Exhibition (Proceedings) 47(II), 929-940. Priestley, M. J. N., and Seible, F. (1995). "Design of seismic retrofit measures for concrete and masonry structures." Construction and Building Materials 9(6), 365377. Sittipunt, C., Wood, S. L., Lukkunaprasit, P., and Pattararattanakul, P. (2001). "Cyclic behavior of reinforced concrete structural walls with diagonal web reinforcement." ACI Structural Journal 98(4), 554-562. Triantafillou, T. C. (1998). "Composites: A ne w possibility for the shear strengthening of concrete, masonry and wood." Composites Science and Technology 58(8), 12851295. Tumialan, J. G., San Bartolome, A., and Na nni, A. (ND) "Strengthening of URM Infill Walls by FRP Structural Repointing." Ninth North American Masonry Conference Clemson, SC.

PAGE 136

123 BIOGRAPHICAL SKETCH William Swanson was born in Rabat, Morocco, on March 11, 1953. His family remained there for only 1 more year before returning to Minneapolis, Minnesota. William lived there for 16 years and then served a stint in the United States Marine Corps. He attended Montana State University for 2 years and then moved to New Mexico, graduating from New Mexico State University with a BSCE in 1980. He worked as a structural design engineer for several aerospace companies in Washington, California, and Florida before enrolling in a gr aduate program in structural engineering at the University of Florida in 2000.


Permanent Link: http://ufdc.ufl.edu/UFE0003243/00001

Material Information

Title: Glass Fiber-Reinforced Polymer (GFRP) and Steel Strengthening of Unreinforced Brick Masonry Piers
Physical Description: Mixed Material
Copyright Date: 2008

Record Information

Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
System ID: UFE0003243:00001

Permanent Link: http://ufdc.ufl.edu/UFE0003243/00001

Material Information

Title: Glass Fiber-Reinforced Polymer (GFRP) and Steel Strengthening of Unreinforced Brick Masonry Piers
Physical Description: Mixed Material
Copyright Date: 2008

Record Information

Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
System ID: UFE0003243:00001


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GLASS FIBER-REINFORCED POLYMER (GFRP) AND STEEL STRENGTHENING
OF UNREINFORCED BRICK MASONRY PIERS
















By

WILLIAM P. SWANSON


A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF ENGINEERING

UNIVERSITY OF FLORIDA


2004

































Copyright 2004

by

William P. Swanson















ACKNOWLEDGMENTS

Acknowledgements go to the National Science Foundation and the Marketing

Developing Alliance for the Composites Industry for their financial support of this

research. I thank Dr. H. R. Hamilton for providing me the opportunity to perform this

work and helping me along the way. Dr. Ronald A. Cook and Dr. Gary Consolazio

deserve thanks as members of my committee.
















TABLE OF CONTENTS



A C K N O W L E D G M E N T S ................................................................................................. iii

LIST OF TABLES .................... .. ............. ............................... vi

LIST OF FIGURES ............ ............................................. viii

A B S T R A C T .............................................. ..........................................x iii

CHAPTER

1 INTRODUCTION AND OBJECTIVES ....................................... .................

In tro d u ctio n .................................................................................. 1
R research O bjectives.......... ................................................................ ........ .... .4

2 EXPERIM EN TAL PROGRAM .............................................................. ............... 6

T est Sp ecim en s ................................................................... .............................. . 6
M material properties......... .. .......................... .. .................... ................ ......... .. ... ..
GFRP Com posite Reinforcem ent ........................................ ........................... 8
Steel R einforcem ent .................. ........................... ...... .................... 11
T e st S e tu p .......................................................................... 1 3
T est P ro cedu res .................................................. ................ 14
Instrumentation .................................... .......................... .... ....... .15

3 EXPERIMENTAL RESULTS ............................................................................19

Specim en B behavior ............................................................... .......... 19
Load-Displacement Envelopes .............................................................. .. ...... 29
Ductility Of M asonry System s .......... ........................................... ....................30
Com putting Predicted Capacities........................................... .......................... 33

4 CON CLU SION S .................................. .. .......... .. .............36

APPENDIX

A LITERA TU RE REV IEW ...........................................................................37










B SPECIMEN CONSTRUCTION............................................ ........................... 50

C EXPERIMENTAL PROGRAM............................................................. ...............58

D SPECIMEN DETAILS AND RESULTS...................... ....... ............... 75

L IST O F R E F E R E N C E S ........................................................................ .................... 122

BIOGRAPHICAL SKETCH ............................................................. ..................123
















































v
















LIST OF TABLES

Table p

1 M material Properties .................... ........ .......... ...... .... .. .. ........ ..

2 GFRP configuration Tests Ih 5....................................... ......................... 10

3 Instrum ent type and function......................................................... ............... 16

4 R esu lts of cy clic testing ......................................... .............................................22

5 m factors per FEMA 273 for specimens with steel...............................................32

6 Curvature ductility factors specimens reinforced only with GFRP.....................32

7 M measured and Calculated Lateral Capacities ............... ............ .....................35

8 Instrum entation description........................................................... ............... 65

9 Individual bricks Compressive strength................................. ............. ...........72

10 Brick prism s Com pressive strength ............................................ ............... 72

11 Steel rebar Tensile strength......................................................... ............... 73

12 Glass rebar Tensile strength ......... .................................... ........................ 73

13 FRP bond tests Wire brushed wall........................... ......................73

14 FRP bond tests Sand blasted w all ........................................ ....... ............... 73

15 F R P description test h ........................................ ...................... .....................76

16 Crack occurrence ....... .. ............................. .... ...... ....................... 77

17 F R P description T est li ........................................ ...................... .....................8 1

18 C rack occurrence Test li............................................. .............................. 82

19 F R P description test 2 ........................................ .............................................86

20 Crack occurrence Test 2 .............. .............................................. ............... 87









F R P d description test 4 ........................................ ............................................9 1

Crack occurrence Test 4 ....................................... ..................... ............... 91

F R P description test 5 ........................................ .............................................96

C rack occurrence test 5 .............................................................. .....................96

FR P description Test 6 ............................................... ............................. 101

C rack occurrence test 6 ............................................... ............................ 101

FR P description T est 7........................................ ..... ................. ............... 105

C rack occurrence Test 7 .............................................. ............................ 106

F R P description T est 8 ........... ........................................................................ 110

Crack occurrence Test 8 .............. ... ........ ....................... 11

FRP description Test 9 .............. ................................................................. 117

Crack occurrence Test 9 ................ ......... .. ........................ ............... 118
















LIST OF FIGURES


Figure p

1 Pier strengthened w ith FR P ............................................................................ 4

2 M odel for specim ens ....................................................... ...... ... .... .4

3 C configuration of specim ens ............................................... ............................ 7

4 General GFRP laminate placement...................................................................... 9

5 Location and orientation of steel reinforcement ............................................... 12

6 T est setup view from the N orth ....................................................................... ... 13

7 String and linear pot location for all walls ................................................... 15

8 GFRP strain gauge locations for Specimen Ih, li, 5, 6 .......................................16

9 Steel strain gauge locations for Specim en 2.................................. ............... 17

10 GFRP and steel strain gauge locations for Specimen 4 .......................................17

11 GFRP and steel strain gauge locations for Specimen 7 .......................................17

12 Glass rebar strain gauge locations for Specimen 8 ..............................................17

13 GFRP and steel strain gauge locations for Specimen 9 .......................................18

14 Cyclic behavior of Test Ih GFRP laminate only ................................................19

15 Cyclic behavior of Test li Specimen Ih repaired with spray-up GFRP ...............20

16 Cyclic behavior of Test 2 GFRP laminate, 2-#3 reinforcing steel bars ..............20

17 Cyclic behavior of Test 4 GFRP laminate, 4-#3 reinforcing steel bars ...............20

18 Cyclic behavior of Test 5 GFRP laminate only ......................................... 20

19 Cyclic behavior of Test 6 GFRP Pre-impregnated only ....................................21

20 Cyclic behavior of Test 7 GFRP laminate, 2-#3 reinforcing steel bars ...............21









21 Cyclic behavior of Test 8 GFRP #3 reinforcement.............................................21

22 Cyclic behavior of Test 9 GFRP laminate, 2-#3 reinforcing steel bars.................21

23 Crack pattern for test 2 (North face) ............................................. ............... 24

24 A Test 2, east edge of pier. B -Test 4, south side east edge of pier....................25

25 In-plane m ovem ent base of pier............................................................. .......... 26

26 C rack pattern for test 8 ................................................. ................................ 27

27 Strain measured in GFRP bar A at north end of pier. .......... ............. ............28

28 C rack pattern for test 9 ......... ................. ................................... ..........................28

29 Backbone curves specimens with no steel.................................. .................29

30 Backbone curves specimens with steel ...................................... ............... 29

31 Force-displacement curve for Unreinforced Masonry strengthened with fully
bonded GFRP composite and inadequately bonded GFRP composite ....................30

32 Method for obtaining values to calculate curvature ductility..............................33

33 Schematic for predicting specimen capacity ............. ..............................................35

34 Illustration of specim en m odel ...................................................... .............. 50

35 Specim ens II VIII Tests Ih, li, 2, 4, 5, 6, 7, 8 .............. .................................. 51

36 Specim en I Test 9............. ............................... ............ ............ 51

37 A Base lintel, B First course of brick being laid ............................................52

38 A Brick laying and B grouting ........................................ ........................ 52

39 A and B L saying pier bricks ......... ................................................ ............... 53

40 L saying header course ....................................................................... ..................53

41 Com pleted specim en (no top lintel) .............................................. ............... 53

42 Applying FRP to a concrete block wall ....................................... ............... 56

43 E poxy injection system .................................................. .. .. ........................ 56

44 A and B Injecting epoxy into rebar hole............................................................. 57

45 Typical steel rebar configuration...................... ..... ............................ 57









46 Test stand N orth elevation ............................................. ............................ 59

47 T est stand E ast elevation .......................................................................... .....60

48 Specim en installed in test stand ........................................ .......................... 62

49 Reaction fram e ......................... ........... .. .. ......... ..... ..... 62

50 Lateral movement prevention struts......................................................................63

51 Wall end of a lateral movement prevention strut................................ ..............63

52 One of tw o 'gravity' load springs ..................................................... ............ 64

53 Specim en handling fixture ............................................... ............................ 64

54 Instrumentat locations (string and linear pots) all walls .......................................65

55 FRP strain gauge location Tests lh, li, 5, 6................................... ............... 67

56 FRP and steel strain gauge locations Test 4 .................. ............... ............... 67

57 FRP and steel strain gauge locations Test 7................................... ...............67

58 Glass rebar strain gauge locations Test 8.................................... ...............68

59 FRP and steel strain gauge locations Test 9................................... ...............68

60 Steel strain gauge location Test 2 ........................................ ....... ............... 68

61 Steel strain gauge installation........................................................ ............... 69

62 LabVIEW program m ain screen ........................................ ......................... 70

63 MTS Signal Generation program screen..............................................................70

64 FR P layup N orth side .................................................. .............................. 76

65 FR P layup South side .................................................. .............................. 76

66 C rack pattern at failure ............................................................................. ... ........77

67 A N orth side. B South side.......................................... ........................... 77

68 Progression of glass debonding (black lines) ............. ..........................................78

69 D ata reduction plots ....................................................... ...... ...... ... .. 79

70 A Spray on/ FRP layup North side. B FRP layup South side ..........................81









71 C rack pattern at failure ....... ........................................................... ............... 82

72 O overall view N orth side ............................................... ............................. 82

73 T ear in FR P ................................................................... 83

74 D ata redu action plots ........................................................................ ...................84

75 A FRP layup North side. B FRP layup South side............................................86

76 Crack pattern at failure A North side, B South side...........................................87

77 A Overall view North side. B view South side.............................................88

78 A East edge of pier. B South side crack pattern..............................................88

79 FR P pulloff- N north side ............................................... ............................... 88

80 D ata reduction plots test 2 .................................. ........................ ............... 89

81 FRP layup A North side, B South side................................... .................91

82 Crack pattern at failure A North side, B South side........................................92

83 A- North side, B -North side, east edge of pier ........... .......... ............... 92

84 A South side, east edge of pier, B South side lower center of pier ..................92

85 D ata reduction plots Test 4................................. ............... ............... 94

86 FRP layup North side (No FRP on south side) ............................................. 96

87 Crack pattern at failure North side (Glass rupture is vertical strip A, east) ..........97

88 Crack pattern at failure South side ............................................. ............... 97

89 A overall view, B West edge of pier ............ ............................. ...............98

90 A Glass break in vertical strip 'A' east edge, B Delamination pattern..............98

91 D ata reduction plots Test 5............................................... ............... 99

92 FRP layup -North side (No FRP on south side) ......................... ........ ........... 101

93 Crack pattern at failure A North side, B South side
( glass rupture is 'A straps) ....................................................................... ..... 102

94 A Overall view N orth side, B South side.......................................................102

95 N north side after test .................................................................... .. ............ 102









96 Data reduction plots test 6 ................................ ......... .. ............... 103

97 FRP layup Test 7 ................. ........ .......... ........ .. .. .. ............ 105

98 Crack pattern at failure A North side, B South side......................................106

99 A Overall view, B FRP delamination, east edge of pier ...............................107

100 A -North side, west edge of pier, B South side, west edge of pier................. 107

101 A delamination North side, B south side .................................. ............... 107

102 D ata reduction plots test 7 ...................................... ............. .......................... 108

103 Glass rebar installation/location test 8 ................................... ....................... 110

104 A Pier section glass rebar location, B typical single bar 3/inch groove, C -
Vertical bars 3/inch groove. Horizontal bar crosses outside ............................111

105 Crack pattern at failure A North side, B South side..................................112

106 Overall view North side ........... ... ............... ............... 13

107 North side of base A east edge, B west edge ............................... ..........13

108 South side of base A west edge, B east edge ................................... ................ 113

109 D ata reduction plots Test 8 .................................................... ...................115

110 FRP layup North side Test 9 .............. ... .....................................1.17

111 Crack pattern at failure A North side, B South side.....................................118

112 Overall view N orth side ....................................................................... 119

113 A South side, B N orth side .................................................... .................. 119

114 D ata reduction plots Test 9...................................................... ............... 121















Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Engineering

GLASS FIBER-REINFORCED POLYMER (GFRP) AND STEEL STRENGTHENING
OF UNREINFORCED BRICK MASONRY PIERS

By

William P. Swanson

May 2004

Chair: H. R. Hamilton
Major Department: Civil and Coastal Engineering

This thesis presents research on the strengthening of unreinforced masonry (URM)

piers with glass fiber-reinforced polymers (GFRP) in conjunction with ductile

reinforcement. Eight brick masonry pier specimens were strengthened with a

combination of GFRP composite strips and reinforcing steel or GFRP alone. Specimen

construction included the pier and a portion of the masonry just below the pier. GFRP

composite strips were strategically placed to improve flexure and shear strength in the in-

plane direction. Steel dowels were added to the specimens by drilling down diagonally

through the pier and base and securing the dowels with epoxy. This steel was designed to

yield prior to rupture of the GFRP composite, giving a ductile response.

Improvement in lateral capacity of up to three times the capacity of URM rocking

mode was achieved. Drift capacities ranged from 0.29% to 1.6%. Splitting of the

masonry was shown to be a controlling factor in the extent of yielding attained in the

steel dowels.














CHAPTER 1
INTRODUCTION AND OBJECTIVES

Introduction

Buildings that are made of wood historically, and wood or steel or steel reinforced

concrete in recent times tend to fare well when exposed to earthquake induced loads.

This is due to the flexibility of wood and the ductility of steel. Steel has the ability to

deform large amounts without failing, while dissipating a large percentage of the energy

imparted to the building during an earthquake, making it an excellent material for use in

areas that may expect earthquake induced loading (whether on buildings made with a

completely steel structure or a concrete structure reinforced with steel). This is especially

true in the most recent of modern times (i.e., within the last decade, where structural

design and earthquake science have both reached levels of maturity that can make

buildings of an unprecedented ruggedness).

Prior to the advent of modem reinforced masonry, buildings were constructed with

unreinforced masonry (URM) for many years. URM structures do not perform well

during earthquakes and can cause significant property damage and loss of life. One

reason is that they were designed before structural response to ground motion was well

understood. Another reason is that URM construction is inherently brittle and does not

provide ductile response during earthquake loading. This lack of ductility can lead to

significant local or widespread instability and ultimately, collapse, during ground motion.

Thousands of URM structures are currently in service and will remain so for many

more years, provided that they do not get knocked over by an earthquake. Engineers









realize today that the chance for devastating earthquakes is greater than has been

addressed in the past. Conventional means of strengthening URM structures such as

shotcrete have been in use for many years. Other methods include installation of

reinforced concrete shear walls or structural steel frames that ignore the contribution of

the existing masonry to the load carrying capacity of the structure.

Fiber Reinforced Polymer (FRP) composites are made of continuous glass, carbon,

or aramid fibers encapsulated in a resin matrix and can be bonded to a masonry surface to

strengthen an existing structure. These materials can be added to a building with

relatively minor impact on the occupants compared to other methods currently used for

building rehabilitation such as shotcreteing walls or adding new structural components.

It could also be substantially less expensive than methods such as post-tensioning entire

walls roof to foundation. This technique has been evaluated by a number of

researchers and has been used on URM structures. Several FRP composite

manufacturers market systems specifically for application to masonry structures.

Ehsani, Saadatmanesh, and Velazquez-Dimas (1999) built three half-scale

unreinforced clay brick walls, retrofitted them with vertical FRP strips and subjected

them to cyclic out-of -plane loading. They found that the mode of failure was controlled

by tensile failure when wider and lighter composite fabrics were used and by

delamination when stronger fabrics were used. They report that although URM walls and

composites behave in a brittle manner, the combination resulted in a system capable of

dissipating some energy. Deflections as much as 2.5% of the wall height were observed

for walls with unidirectional fabric; these walls deflected almost 14 times the maximum

allowable deflection according to the latest masonry specifications. Some of this energy









dissipation was attributed to the removal of brick material with the composite as it

progressively delaminates. Our study observed deflections up to 1.5% for specimens

reinforced only with GFRP.

Researchers Marshall and Sweeney (2002) performed in-plane shear tests on 4-foot

by 4-foot unreinforced double-wythe brick wall specimens and lightly reinforced single-

wythe concrete masonry unit (CMU) wall specimens. These specimens were tested with

various configurations of glass and carbon FRP applied to them. They found that the

strength of the specimens can be increased with the application of FRP composites,

however in all cases the failure mode changed to a less ductile mode. They felt that the

next step in this line of investigation would be to develop configurations of FRP

reinforcement that can prevent failure modes such as X-cracking while transferring the

failure to a more ductile mode such as bed joint sliding or rocking prior to toe crushing.

Holberg and Hamilton (2002) proposed a system incorporating two materials,

glass fiber reinforced polymers (GFRP) and steel, and investigated several configurations

on full scale masonry specimens. These utilized two different types of steel connections,

internal and external (Figure 1). The drift capacities of these specimens reached up to

1.7%. The lateral capacities were nearly doubled compared to an unreinforced specimen.

The vertical GFRP strips are designed to provide enough additional strength to

enable the pier to resist the shear and flexural stresses imposed on it during a seismic

event. The steel is designed to yield at the pier/sill interface prior to failure of the GFRP

composite.









Lateral Load

FRP improves shear
Steel bonded between pier and flexural strength
and sill adds ductility |


I


I


Figure 1: Pier strengthened with FRP.

Research Objectives

The intent of this research is to further develop and evaluate the rehabilitation

mechanism utilizing a hybrid system for the reliable dissipation of energy within a brick

building during a seismic event.

Previous URM research has focused primarily on pier segments. This approach

inherently directs the focus on the pier without examining the behavior at the pier

interface. Figure 2 shows an illustration of the pier and base portion of a building that

was used to develop the specimen configuration for the tests performed in this research.

This area was chosen for modeling because it is the area of a building that is most

susceptible to damage during a seismic event. Various methods of anchoring the pier to

the base were investigated.

I^ I --- I o ,,,,


Figure 2: Model for specimens


' -1






5


The system under investigation consists of GFRP and steel added to strategic areas

of a brick wall. The GFRP can add strength where it is desirable while the steel can

provide ductility to the system. Properly placed GFRP has the potential to direct seismic

energy to the added steel, allowing it to be dissipated through the ductility of the steel.














CHAPTER 2
EXPERIMENTAL PROGRAM

Eight clay brick specimens were constructed and tested. The behavior of the pier

ductile connection and base subjected to in-plane cyclic loading was investigated. The

experimental parameters were the amount and type of GFRP composites and the amount

of steel which was added to the basic wall specimen.

Test Specimens

The specimens were constructed in running bond using type N mortar. A local

masonry contractor (Painter Masonry, Inc.) was hired to build the wall specimens. ASTM

C62 grade MW 8 inch clay bricks were obtained locally from Florida Rock Industries

Inc, located in Gainesville FL. Double-wythe construction gave a thickness of 8 in. (203

mm). The outline of the specimens consisted of a 48-in. square pier resting on a 112 in.

(2.8 m) long by 16-in. (0.4m) tall base (Figure 3).

Precast concrete lintels were used to support and move the specimens. The lintels

were reinforced longitudinally with two no. 6 steel reinforcing bars and filled with ready-

mixed concrete. The length of the base lintels was 112 inches (9 feet, 4 inches). A

second lintel was set on the top of each pier using the type N mortar. A header course

was laid at the fourth course and at each sixth subsequent course. Collarjoints were

filled solid with mortar. The first course in Specimen I was laid with half-length units at

each end instead of the full length shown in Figure 3. It is believed that this minor

coursing difference did not effect the performance of the specimen.

























64 in.
Figure 3: Configuration of specimens

Material Properties

Materials used for building the walls were tested individually to determine their

characteristics (Table 1). Individual brick units and prisms made with four units were

tested in compression to failure. The prisms were made using the mortar from the

batches used to construct the walls. The #3 steel rebar and the unidirectional fiberglass

were tested in tension until fracture. These tests were performed to ASTM standards.

All tested samples were taken randomly from stock. The GFRP samples were cut from a

section of cured GFRP composite and then milled to a 1 in. width. The average width

of these was 1.04 in. (26.4 mm) and the average thickness was 0.09 in. (23.1 mm).

Preparation and testing of the GFRP followed ASTM D3039.









Table 1: Material Pro erties
Average No. of
Material Test Strength Specimen
Unit compressive 7790 psi
Bricks strength (54 MPa) 7
Brick Prism compressive 4230 psi
Prisms strength (29 MPa) 7
#3 Steel Tensile yield 62 ksi
rebar strength (427 MPa) 4
GFRP Mfgrs. specs. 110 ksi
#3 rebar tensile strength (758 MPa) na
GFRP unidirectional Tensile 2.8 kips/in. width
coupons strength (500 N/mm) 5
GFRP bond GFRP tensile Wire brushed 706 psi (4.9 kPa) 4
bond strength Sand blasted 801 psi 3
(5.5 kPa)
Pre-preg Mfgrs specs.
GFRP tensile strength 1.2 kips/inch (210 N/mm) na

Glass Fiber Reinforced Polymer Reinforcement

Six of the eight specimens were strengthened with varying widths and lengths of

GFRP laminate, 27 oz/yd2 (7.5 N/m2), bonded to the brick surface with a two- part epoxy.

The walls were either cleaned with a power wire brush or sandblasted and then brushed

clean prior to the application of the GFRP. One of the specimens was reinforced with

spray-on chopped fiberglass/resin and retested. The seventh specimen was strengthened

with a unidirectional grid of pre-impregnated fiberglass. This is a high strength material

made by bonding E-glass fiber rovings with epoxy resin in a controlled factory

environment. It was bonded to the specimen using a low modulus two-part epoxy. The

eighth specimen was reinforced with near-surface mounted #3 GFRP bars.

Quantity and placement of the GFRP for the pier and base were determined using a

strut and tie analysis and basic principles of mechanics. Figure 4 shows the location of

the general placement of the GFRP laminates and Table 2 details GRFP composite

configurations and placement. Testing of specimen Ih resulted in very little damage to









the masonry (laminate A debonded). Consequently, the specimen was revised (specimen

li). Chopped fiber spray up system was applied to the north face and the specimen was

retested.

L L2~ N
E A (2 PL)

D
B
/ C7





Figure 4: General GFRP laminate placement

The vertical strips (A) increased the in-plane flexural strength and the diagonal

strips (D) increased the diagonal tensile strength of the pier. (A) was 3 inches wide on all

specimens where used except test 2 which was two inches and test 6 which was 6 12

inches of the GFRP grid. The vertical strips of chopped glass spray-up for test li were 8

in. wide. (D) was 3 inches wide where used except on test 6 which was 7 in. of GFRP

grid. Bi-directional GFRP laminate (grid for test 6) was added across the top of the pier

(E) at the pier/lintel interface (12 in. x 48 in.) to reduce the likelihood of a separation of

these two components during testing.

Laminate B (6 in. x 112 in.) provided bending resistance and laminate C (18 in. x

112 in.) provided shear resistance in the base of the specimen.

Table 2 shows the complete GFRP patterns for the individual specimens. The

chopped fiberglass shown on the specimen for test li is labeled (F). The pre-impregnated

grid is labeled (G) on the specimen for test 6 and the helical wrap glass rebar for the

specimen for test 8 is labeled Glass Rebar.







10


Table 2: Glass Fiber Reinforced Polymer configuration Tests lh to 5
North Face South Face
Specimen

lh fE 1 (2 PL)

B D C




F E X\(2 PL)
c D B
B



2 A
E A E 12PL
(2 PL) C D C
B/ B




E _PL E A
D L2 PL)
D -B



5 L- I
Si PL)
D BC7 No GFRP on south face









Table 2: GFRP configuration (cont.)
Specimen North Face South Face

6
6G
ALL
STRIPS) No GFRP on south side



7 A
E PL
D No GFRP on south side



8 GFRP
NSM
7 PL No GFRP on south side



9 LI / I
C A
(2 PL)
B (2PL) No GFRP on south side



Steel Reinforcement

Steel reinforcement (#3) was installed in specimens for tests 2, 4, 7, and 9 in an

attempt to achieve a ductile failure. The size and number of bars chosen were

coordinated with the amount of GFRP used so that the steel would yield prior to a failure

of the GFRP composite.

Steel reinforcing bars were installed as shown in Figure 5 by drilling a 3 in.

diameter hole diagonally down, starting on the pier (broad face) 16 inches up from the

pier/base and down through the wall to emerge at the bottom of the base on the far side of

the wall (Figure 5). Each hole was filled with a two-part, high-modulus epoxy (Master

Builder's Concresive 1420) by inserting a tube to the bottom of the hole and withdrawing









it as the epoxy was injected through it. The reinforcement was then coated with epoxy as

it was inserted into the hole with strain gauge wires coming out of the top of the hole.

The strain gauges were covered with tape and shrink wrap tubing for a length of four

inches. This gave a four inch unbonded length of the steel to the brick allowing the steel

strain to be distributed over this four inch length. Figure 2-3 shows the location of the

added steel.


Figure 5: Location and orientation of steel reinforcement











Test Setup

The test setup was designed to load the masonry specimens in plane (Fig. 1). The

inverted 'T' configuration, representing the lower half of a wall pier between two

windows, required tie-down points at each end.

A 55 kip MTS hydraulic actuator was placed between the top of the cap and the

reaction frame. This actuator was part of a closed-loop hydraulic loading system. The

system was controlled by an MTS 407 controller. The controller used a sinusoidal

voltage output from the data acquisition system to impart the desired displacements to the

cylinder. The actuator has a built-in load cell ( a + reading is specimen pulled to the

West, a reading is pushed to the east) that was used to acquire the load imposed on the

specimens during testing. Extension and retraction of this device simulated the loading

conditions that would be experienced by a shear wall during ground movement parallel to

the wall. Figure 6 shows the testing setup and configuration.

ALL THREAD
4 KIP/IN SPRING -\ ROD


(QTY 2)

2000 # CAP



East


50 KIP HYDRAULIC ACTUATOR


REACTION FRAME


West


STRONG FLOOR
(THICK REINFORCED CONCRETE SLAB)


Figure 6: Test setup view from the North









Part of the gravity load was simulated by applying a downward force of 6.0 kips to

the concrete cap with two pre-compressed rail car springs. This force combined with the

weight of the concrete cap (2.0 kips [8.9 kN] ), pier, and lintel gave a load of

approximately 9.0kips (40 kN), creating an axial stress of 25 psi (172 kN).

National Instruments LabVIEW software was run on a personal computer along

with a 16 bit data acquisition card for data acquisition. Linear and string potentiometers

were used to measure wall displacements. Foil strain gauges were applied to the steel and

GFRP to measure their strains.

Test Procedures

The ICBO Acceptance Criteria for Concrete and Reinforced and Unreinforced

Masonry Strengthening Using Fiber-Reinforced Composite Systems (ACI125) (ICBO

1997) was followed to determine the displacements to be imposed for each test. For

walls with no steel the yield point was taken as the displacement that was expected to

cause cracking and initiate rocking of an unreinforced specimen. For walls with steel

reinforcement, yield was taken as the displacement at which the steel was expected to

yield. These yield displacements were assigned t1 = 1. The displacements then imposed

during testing were fractions or multiples of t = 1/4, 1/2, 1, 2, 3, 4, 6, 8, 10, 12, 16,

etc. The specimens were loaded in displacement control with three complete cycles for

each displacement level :. A complete cycle was one displacement [t in each of the

positive and negative directions. The specimens were loaded through increasing [t until

lateral load carrying capacity was lost or the specimen was deemed unstable.









Instrumentation

Figure 7 shows the location of either the instrument itself or the attachment point to

the wall for the instrumentation that was common to all specimens. The type of each

device shown is listed in Table 3 along with the measurement taken. Each device was

either mounted to the wall with its probe contacting or attached to a solid stand or the

device was mounted to a stand with its probe contacting or attached to the wall. The

figure does not necessarily show the location of the instrument but the location where the

measurement is being taken. The locations of GFRP and steel strain gauges are shown in

Figure 8 to Figure 13.

All stands were heavy and solidly connected to the lab floor. Carol and Diane were

located as shown for several tests and then moved to the west side (same relative

location) for the remainder of the tests. The naming convention for the instruments was

chosen in order to give each instrument a unique identity, facilitating their placement and

setup.

East West
SCarol
,,.. .
(" 1essa (oop)
.. ... ,,, Ian

Emily

SKarl Jim (oop = out of plane)


Figure 7: String and linear pot location for all walls









Table 3: Instrument type and function

Name Type Measurement Shown
Carol String pot Horizontal Displacement in plane Attach point
Gina String pot Vertical Displacement in plane Attach point
Flo String pot Vertical Displacement in plane Attach point
Emily Linear pot Horizontal Displacement in plane Instrument
Diane String pot Horizontal Displacement in plane Attach point
Will Linear pot Horizontal Displacement out of plane Contact point
Vanessa Linear pot Horizontal Displacement out of plane Contact point
Ian Linear pot Vertical Displacement in plane Instrument
Henry Linear pot Vertical Displacement in plane Instrument
Karl Linear pot Vertical Displacement in plane Instrument
Jim Linear pot Vertical Displacement in plane Instrument
Linda Strain Gauge Vertical strain FRP or glass rebar
Nancy Strain Gauge Horizontal strain FRP or glass rebar
Marie Strain Gauge Vertical strain FRP or glass rebar
Oscar Strain Gauge Steel strain
Pete Strain Gauge Steel strain
Quin Strain Gauge Steel strain
Rick Strain Gauge Steel strain


SLinda
S Nancy



Marie
(Ih, li, 6 only)


Figure 8: GFRP strain gauge locations for Specimen Ih, li, 5, 6
















/OPete


Figure 9: Steel strain gauge locations for Specimen 2


on I


-Rick
Linda
S Quin ..T-
NM1INIanc


Figure 10: GFRP and steel strain gauge locations for Specimen 4





S Linda


Oscar


Pete


Figure 11: GFRP and steel strain gauge locations for Specimen 7


Figure 12: Glass rebar strain gauge locations for Specimen 8


Oscar


y


Oscar













Linda

Oscar Pete


Figure 13: GFRP and steel strain gauge locations for Specimen 9
















CHAPTER 3
EXPERIMENTAL RESULTS

Specimen Behavior

Cyclic behavior of each specimen is illustrated in the load-drift plots shown in

Figure 14 through Figure 22. A single test was performed on each specimen.

Consequently, test numbers correspond directly with the specimen numbers described in

previous sections. Drift was calculated as the in-plane displacement of the pier divided

by its height. Horizontal lines have been added to the plots that indicate the loads at

which the GFRP was calculated to rupture for specimens with no steel and the loads at

which the steel was calculated to yield for specimens with added steel. Details of the

calculations are presented in a later section.

20 89

10 44.5

0 I
01 1 0
0 _j
-10 -44.5

-20 -89
-2 -1 0 1 2
Drift (%)

Figure 14: Cyclic behavior of Test lh GFRP laminate only



























-2 -1 0
Drift (%)


Figure 15: Cyclic behavior of Test li


20

10

0
o
j-10

-20


Specimen Ih repaired with spray-up GFRP


89

44.5
z
0

-44.5

-89


-2 -1 0
Drift (%)


Figure 16: Cyclic behavior of Test 2


20

-10

0
o
2-

-10

-20
-2 -1


Figure 17: Cyclic behavior of Test 4-


-GFRP laminate, 2-#3 reinforcing steel bars


0

-44.5

-89
0 1 2
Drift (%)

- GFRP laminate, 4-#3 reinforcing steel bars


20

-10

0

-10

-20


1 1


-2 -1 0 1 2
Drift (%)

Figure 18: Cyclic behavior of Test 5 GFRP laminate only


89


44.5


0
0
-_j
-44.5


-89


1 2


1 2


89

44.5
z
0

-44.5

-89











20

10

-0
0

-10

-20


-2 -1 0
Drift (%)


89

44.5

-I-----. 0 -^
0

-44.5

-89
1 2


Figure 19: Cyclic behavior of Test 6 GFRP Pre-impregnated only


20

10

0
Co
10

-20


-2 -1 0
Drift (%)


Figure 20: Cyclic behavior of Test 7


GFRP laminate, 2-#3 reinforcing steel bars


89


44.5


0 -
-j
-44.5


-89


-3 -2 -1 0 1
Drift (%)


Figure 21: Cyclic behavior of Test 8 GFRP #3 reinforcement


20

10
(n
0

S-10

-20


-2 -1 0
Drift (%)


Figure 22 Cyclic behavior of Test 9 GFRP laminate, 2-#3 reinforcing steel bars


89

44.5

0

-44.5

-89


1 2


2 3


89

44.5
z
0-^
0

-44.5

-89


1 2


440


I I









Table 4 gives peak lateral loads and limiting modes of failure for each test. The

peak loads were the maximum force detected during the cycling and do not necessarily

correspond to the maximum drift ratios shown. The maximum drift ratios were

determined by taking the maximum lateral movement achieved at the top of the specimen

and dividing it by the height of the pier (48 in.) and multiplying this by 100.

Table 4: Results of cyclic testing

Maximum Maximum Limiting
Test Drift (%) Lateral Load (kips) Mode
+ 0.29 + 9.88 GFRP bond failure
lh -0.29 -10.25 Pier rocking
+0.39 +17.76 GFRP rupture
li 0.36 -18.07 Pier rocking
+0.96 + 15.04 Diagonal tension
2 1.32 12.87 Pier rocking
+0.58 + 17.57 Pier rocking
4 0.51 17.66 Tensile failure of brick
+0.50 + 11.95 Pier rocking
5 0.52 -11.78 GFRP rupture
+ 1.26 + 15.40 Pier rocking
6 1.29 -15.56
+ 1.01 + 13.73 Pier rocking
7 -1.02 -12.31 Diagonal tension
+ 1.54 + 10.10 Mortar joint tensile failure in base
8 -1.62 -11.20
+ 0.65 + 11.51 Mortar joint tensile failure in base
9 0.78 -10.36

The following presents a brief summary of the behavior of each specimen during

cyclic testing. Observations are keyed to the displacement ratio [t or % drift. For these

discussions debonding is a separation at the laminate-masonry interface; substrate failure

is a cohesive failure in the masonry; and delamination is a separation of laminate layers.

Test lh: Specimen damage initiated at 1 = 1/2 (drift = 0.28 %)with debonding of

GFRP laminate A. The debonding initiated at the Pier/Base interface, debonding









commencing at [t = 1/2 and progressing from interface, and progressed incrementally

with each displacement cycle. This prevented the intended failure mode from occurring,

which was rupture of "A" at the pier/base interface.

Laminate A was completely debonded at 0.48 % drift at which point the test was

terminated. It was thought that perhaps out-of-plane movement occurred due to eccentric

reinforcement (GFRP strips placed on one side only). The measured out-of-plane

movement, however, was only 0.005 in. (0.13 mm) at 0.09 % drift, which is probably too

small to have initiated the debonding.

To address this question, the pull-off bond strength of the GFRP composite was

investigated. Two-in. (50mm) diameter disks were adhered to the surface of the GFRP

composite. A core drill with the same diameter as the disk was used to cut through the

GFRP composite and lightly into the brick. The force required to pull the disk off of the

masonry was measured. These tests were performed on two differently prepared brick

surfaces, one was sandblasted and the other wire brushed with a power wire brush.

Failure modes were cohesive through the brick indicating adequate bond. The material

tested for bonding was the + or 45 degree weave material while the GFRP that peeled

off during wall testing was the unidirectional glass.

After laminate A debonded completely, the specimen reverted to a rocking

response mode, causing very little damage. Consequently the specimen was "repaired"

with a spray up system described previously.

Test li: After completion of test Ih, spray on chopped fiberglass was applied to

the face opposite that of the GFRP laminate. Spray-on GFRP began cracking at the

pier/base interface on the east edge of the west strip. Cracks were first noted at 0.21 %









drift and were oriented parallel to the bed joints. This cracking progressed upward along

the east edge of the strip as displacement increased. GFRP rupture occurred

approximately 12 inches above pier/base interface at 0.54 % drift. The decrease in lateral

capacity associated with rupture is evident in the negative drift quadrant of the plot

(Figure 15).

Excellent bond of the resin to the brick was displayed by the high stiffness and lack

of debonding prior to GFRP rupture.

Test 2: The wall cracked diagonally above one reinforcement and vertically/slight

diagonal next to the other one, first crack occurring at [t = 1 (0.11 % drift). It cracked

across the base of the pier and across the wall at the top of the reinforcement (Figure 23).

The exterior crack pattern reflects brick/reinforcement bond failure and splitting of the

brick.












Figure 23: Crack pattern for test 2 (North face)

A combination of GFRP debonding in laminate A and substrate failure occurred at

base of pier at 1.44 % drift. GFRP that came loose had pieces of brick stuck to it.

Mechanical bond failure (splitting) occurred and is shown in Figure 24. First steel yield

was detected at 0.14 % drift. This specimen had the best performance when considering

ductility. Steel yielding continued until bond failure.

























AB


Figure 24: A Test 2, east edge of pier. B -Test 4, south side east edge of pier

Test 4: Cracking was first observed at 0.14 % drift in a pattern similar to that

observed in test 2. The brick starts to split around the outer reinforcement and the load

redistributes and is picked up by the inner reinforcement, indicated by the slight flat spot

in the positive quadrant of load vs. drift and the drop of load in the negative quadrant.

Strains beyond yield were detected in the last cycle, explaining the more open loops in

the negative direction (Figure 17). Cracks in the pier coalesced into a single crack

surrounding the steel reinforcement. This resulted in the sharp drop in load and

subsequent rocking behavior displayed in the plot. Rocking motion resulted in

permanent movement as indicated by Diane (Figure 25) and the gap in the vertical crack

(Figure 24).










1.0


0.5


0.0
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
Displacement (in.)
Figure 25: In-plane movement base of pier

Test 5: Pier cracked between the top of the reinforcement and the pier/base

interface. Cracking was first observed at 0.26 % drift. The vertical GFRP at both edges

debonded at 0.75% drift starting at the pier/base interface and moving upward during the

last cycle of loading and finally ruptured at pier/base at east end. GFRP debonded and

pulled off pieces of brick at west end. Rocking is indicated by bi-linear curve in Load-

Drift plot.

Test 6: Cracking was first observed at [t = 6 (Drift = 0.53 %). This delayed onset

of cracking can probably be attributed to the large area coverage of the GFRP which

would distribute the stresses evenly across the brick. This could be an advantage holding

a building together. Brick and mortar in the pier/base area failed through successive

cracking on the side away from the GFRP applied surface. Ultimate load carrying

capacity was lost due to rupture of grid which occurred at pier/base interface and a drift

of 1.79 %. No visible damage occurred to the GFRP prior to rupture. The flexibility of

the low modulus epoxy is indicated by the increasing load capacity in the second portion

of the bi-linear curve in the Load-Drift plot

Test 7: Cracking was first observed in bed joint at pier/base interface. During

subsequent displacements cracks appeared in the bed and head joints between the top of

the reinforcement and the base with the cracks progressing across the wall. A and D










laminates started debonding from the brick at the pier/base interface at 0.18 in.

displacement (0.30 % drift) and continued up the wall incrementally with increasing

displacement. This was intermittently spaced, however, and both vertical strips remained

bonded to the brick at the lower ends until the last cycle at which both strips pulled away

from the wall, taking pieces of brick with them.

Test 8: Initial cracking was first observed at [t = 1 (0.12 %). The base failed

through a combination of flexure plus cone pull-out (diagonal tension). Figure 26 shows

the crack pattern that developed in the specimen. The cone pull-out is indicated by the

diagonal cracking alongside the vertical bars and the flexure is indicated by the cracking

along the bottom of the base. It is notable that the pier sustained no cracking.







INSTL.
CRACK
I I I I I I I I I

SINSTL.
CRACK
Figure 26: Crack pattern for test 8

Near complete loss of anchorage resulted in a "restrained" rocking response. Some

anchorage capacity remained because of the GFRP bar B. Strain measurements (Figure

27) indicate that the bar was contributing somewhat to the anchorage restraint. Load

measurement, however, indicates only a slight increase in lateral force over that of pure

rocking response. The steep drop in load in the negative quadrant of the Load diagram

indicates a complete loss of anchorage due to the greater concentration of local cracking

around the north GFRP bars. The positive glass strains shown on strain diagrams for










positive and negative displacement are due to the fact that the vertical reinforcement is

always on the tension side of the neutral axis.

8000

'6000

4000

2000

01 I
-2 -1 0 1 2
Drift (%)
Figure 27: Strain measured in GFRP bar A at north end of pier.

Test 9: The pier stayed together as a unit and exhibited no noticeable cracking.

The strain in the reinforcement at the east end (bar is in tension during positive load) and

the load dropped off simultaneously (at 0.24 % drift). At this displacement the vertical

cracking and the bed joint cracking at the pier base occurred (Figure 28).









I I


Figure 28: Crack pattern for test 9

Continued positive loading caused the base to lift up and the pier to rock. The

reinforcement may have just reached yield as the base started breaking up. This is

notable as it indicates the practical limit to the amount of steel that it is useful to add. For

negative loading it appears that the tension reinforcement was pulling out of the hole.

This would explain the small amount of steel strain along with the small amount of











uplifting of the base while the pier uplift is much greater. The strange bulb shape in the

negative quadrant of the Load diagram shows that the weight of the pier would induce

negative load during bar slippage even though negative displacement was decreasing It

was noticed during specimen demolition that the epoxy holding this reinforcement was

not cured hard. Its color was not typical and incomplete mixing is suspected. The pier

and base both 'walked' to the east.

Load-Displacement Envelopes

A backbone curve was developed for each specimen. These are compiled in Figure

29 and Figure 30. The acceptance criteria for new materials in FEMA 273 were used to

develop these curves.

20

10
0 I I

Test Ih
o Test li
-10 Test 5
Test 6
STest 8
-20
-2 -1 0 1 2
Displacement


Figure 29: Backbone curves specimens with no steel

20

10

0 I I
Test 2
-10 Test 4
Test 7
@2 Test 9
-20
-2 -1 0 1
Displacement (in.)
Figure 30: Backbone curves specimens with steel










The behavior indicated by these plots can be modeled by the force-displacement

graph shown in Figure 31. It has been suggested by Moon, Leon et al. (2002) to take the

initial uncracked stiffness of the specimen as k. After cracking the stiffness can be

represented as a reduced stiffness, k', caused by a combination of cracking, yielding, and

damage to the specimen. If the GFRP composite bond is inadequate then the specimen

stiffness can be reduced further. The second, lower stiffness branch of the curve

represents a lowered stiffness due to bond failure. Failure of the GFRP composite is

shown by the dotted representing a large reduction in strength. Beyond this point the

strength of the specimen is represented by the horizontal and is equal to the strength of an

unreinforced specimen.


Adequate FRP bond



Inadequate FRP bond




Unstrengthened capacity


Drift (%)

Figure 31: Force-displacement curve for Unreinforced Masonry strengthened with fully
bonded GFRP composite and inadequately bonded GFRP composite

Ductility Of Masonry Systems

The focus of this research was to assess several methods of strengthening

unreinforced masonry using GFRP composites. Some of the methods involved a hybrid

system which combined steel and GFRP composites. FEMA 273 outlines requirements









for assessing the ductility of new materials. System or component ductility is quantified

by equation 3-1.

mkQcE> QUD (3-1)

QCE = Resistance capacity

QuD = Seismic demand

k = Knowledge factor relative to material property uncertainty

m = Component demand modifier Ductility capacity coefficient

Equivalent lateral force procedures are used to determine component and system

capacity with this equation. The value ofm increases proportionally with an increase in

system or component ductility. Lateral load demand is reduced through inelastic

response.

When determining m for reinforced masonry, as outlined in FEMA 273, it is

assumed that the reinforcement is a ductile material. These types of material are referred

to as deformation controlled. Materials that fail in a brittle manner (exhibiting linear

stiffness up to severe loss of capacity) are considered force controlled. Individually

masonry and GFRP are brittle materials and would be force controlled but when used

together they behave similarly to a deformation controlled system. Damage sustained by

the system, without going to failure, dissipates energy and increases displacement

capacity. The bilinear stiffness shown in Figure 31 shows this type of behavior. FEMA

273 m factors are determined from force deformation curves and are applicable only to

systems or components with steel reinforcement, these representing a minimum ductility.

The m factors were calculated for the steel reinforced specimens of this current research

using this process and are shown in Table 5.









A moment-curvature analysis was performed to quantify the ductile nature of the

specimens that were reinforced with GFRP only. The factor derived with this method has

been termed qt curvature ductility, and fundamentally differs from the determination

ofm only in that cracking was used for the analysis rather than yielding. Curvature

ductility factors are given in Table 6.

Table 5: m factors per FEMA 273 for specimens with steel

m-factor
Test
Immediate Life
Occupancy Safety
+5.0 +3.7
2 -6.8 -5.1
+6.6 +5.0
4 -6.9 -5.2
+14.8 + 11.1
7 11.1 -5.2
+ 15.4 + 11.5
9 16.9 12.7


Table 6: Curvature ductility factors -


specimens reinforced only with GFRP.


Test 0'I
lh 7.14
5 4.6
6 3.0
8 4.5

qt '. was determined by dividing the ultimate curvature, C,, by the curvature at

first cracking, Ccr, then multiplying this quantity times the ratio of the moment at

cracking, Mcr divided by the ultimate moment, M,:

S'o = (C, M,) (C, M,) (3-2)


Ductility FactorsMoment Curvature Analysis









The values were obtained graphically from a moment curvature diagram for each

specimen using the procedure outlined in Paulay and Priestly (1992). The process used

for specimen Ih is shown in Figure 32.




M -
0


C 'Cr, CG

Curvature
Figure 32: Method for obtaining values to calculate curvature ductility

Analytical procedures developed by Pauley and Priestley (1992) have been adopted

in FEMA 273 to determine displacement ductilities ([ 'A) from curvature ductilities. This

method considers plastic rotations at the base of the component to be limited to a plastic

hinge length, lp, equal to:

p = 0.2 L + 0.04hff (3-3)

where L is the length of the wall and heffis the height of the wall from the base to the

lateral force. Displacement ductility is then determined as:

l 'A = 1 + 3([ 1)( lp/L)(1 0.5 lp/L) (3-4)

Computing Predicted Capacities

Holberg and Hamilton (2001) describe a methodology for the calculation of the

flexural capacity of specimens of the type used in this research. Such capacities were

calculated for two critical sections for the specimens in this study. These sections are 1)

where the GFRP composite ends and the flexural capacity is provided by the steel only

and 2) where the vertical GFRP at the pier edges provide the flexural capacity. Figure 33

shows this relationship. In this figure Pw is the self-weight of the pier and concrete cap,









P, is the axial force provided by the springs, and Q is the lateral load carrying capacity of

the section.

The flexural capacity at either of the critical sections is determined using principles

of mechanics and the traditional rectangular stress block assumption. For an under

reinforced condition, the depth of the stress block, a, is:

a = (A4 +P, + P)/0.85f'mbe (3-5)

be = effective thickness of masonry

A, = cross sectional area of steel

fy = yield of steel

f'm = compressive strength of masonry

The moment capacity, nbar, of the section where the steel provides the flexural

strength is calculated by applying equilibrium to the section:

Mnbar = Ay (d -a/2) + (P, + P,)(1/2 a/2) (3-6)

The load required to yield the steel, i.e. the lateral capacity, is:

Q = Mnbar/hef (3-7)

The moment capacity, I. of the critical section for specimens with no steel is

taken at the pier/base interface and is calculated in a similar manner:

a =(T + P, + Pw)/0.85f'mbe (3-8)

Where:

T= tensile strength of the GFRP composite per inch width, and

w = width of the composite strip. Then, the moment capacity is given by:

Mfp = T (d a/2) + (P, + P,)(1/2 a/2) (3-9)

Q = Mnrp( heff- ,) (3-10)











-F Q -
heff

IS T


Critical Section
Mnfrp
Critical Section
AInbar


Figure 33: Schematic for predicting specimen capacity

Table 7 shows the ratio of the measured lateral force, Qm, at steel yield or GFRP

rupture, to Qnba r Qnfrp along with the calculated capacities. It can be seen that the

predicted capacity is close to the measured capacity for all specimens except 6 and 7

which is an indication of the accuracy of the equation.

Table 7: Measured and Calculated Lateral Capacities
Test Measured Capacity Qnbar Qnfrp Ratio
Qm (kips) (kips) (kips) (Q/ Qnba(Qnfrp))
Ih +9.88 1.15
10.25 8.61 1.19
li + 17.76
18.06 na na
2 + 15.04 1.33
12.87 11.33 1.14
4 +17.57 1.19
17.66 14.8 1.19
5 + 11.95 1.34
11.78 8.89 1.33
6 + 15.40 1.71
15.56 9.0 1.73
7 + 13.73 1.76
12.31 7.8 1.58
8 + 10.10 0.88
-11.20 11.5 0.97
9 + 11.51 1.44
10.36 8.0 1.3














CHAPTER 4
CONCLUSIONS

Eight clay masonry specimens simulating the pier area between two windows of a

low-rise unreinforced brick building were built. These specimens were then modified to

represent a potential rehabilitation to enhance their ability to withstand an earthquake.

The modifications added strategically placed steel rebars and FRP composite strips, FRP

composite strips, or FRP rebars. When steel was added it was designed to yield prior to

the added FRP rupturing.

These modifications show good potential for rehabilitating unreinforced brick

structures to withstand a seismic event. Further research conducted with similar

configurations could help quantify the ductility improvement and help develop

appropriate m-factors for reducing seismic demand.

Key findings and conclusions:

* Rehabilitation of an unreinforced brick structure with steel and FRP composites
resulted in an improvement in ductility, lateral capacity, and energy dissipation. A
drift ratio of 1.64% and a lateral load capacity of almost 18 kips was achieved.
This is 2.4 times the lateral capacity of an unreinforced specimen. Energy
dissipation as the steel yielded was indicated by the open loops in the load-
displacement plots.

* Although it would be desirable to be able to perform modifications to one side only
of a building, it is seen by the performance differences between test 2 (two sides of
wall, 15.7 kip ultimate load, 1.63 % drift) and test 7 (one side of wall, 13.67 kip
ultimate load, 1.52 % drift) that adding GFRP to both sides gives superior results.

* Adding GFRP to the base provides desirable strengthening. The specimen for test
8 had no base reinforcement and broke apart while the base held together on
specimens where it was reinforced.














APPENDIX A
LITERATURE REVIEW

M. R Ehansi, H. Saadatmanesh, and J. I. Velazquez-Dimas (1999)

'Behavior of Retrofitted URM Walls Under Simulated Earthquake Loading' -

These researchers built three half-scale unreinforced clay brick walls, retrofitted them

with vertical FRP strips and subjected them to cyclic out-of -plane loading. Five

reinforcement ratios and two different glass fabric composite densities were investigated.

They found that the mode of failure was controlled by tensile failure when wider and

lighter composite fabrics were used and by delamination when stronger fabrics were

used. They report that although URM walls and composites behave in a brittle manner,

the combination resulted in a system capable of dissipating some energy. Some of this

energy dissipation was attributed to the removal of brick material with the composite as it

progressively delaminates.

J. Gustavo Tumialan, Angel San Bartolome and Antonio Nanni (2003)

'Strengthening of URM Infill Walls by FRP Structural Repointing' This paper

presents results of a testing program dealing with the in-plane behavior of URM infill

walls subjected to in-plane cyclic loading. Four full-scale infill walls were constructed

with unreinforced hollow concrete units inside a reinforced concrete (RC) frame. One

stand-alone (RC) frame was built. The purpose of building and testing this frame was to

determine its stiffness and capacity and therefore to assess the change in behavior of the

lateral force resisting system due to the presence of the masonry infill.









The RC frames were built to be ductile enough that the behavior of the lateral

force resisting system would be controlled by the infill masonry and not the RC

frame.One wall was tested in the unstrengthened condition. Two walls were tested after

strengthening by structural repointing. This method embedded 6.25 mm GFRP bars in

hollowed out bed joints filled with epoxy paste. The fourth wall was reinforced

internally by cutting holes in the top layer of blocks, inserting 6.25 mm GFRP bars into

the vertical cells (spacing of 400 mm) and then filling the cells with grout. There was no

horizontal reinforcement.

Conclusions:

* FRP strengthened specimens reached lateral drifts of 0.7 % with no loss of lateral
load carrying ability. There was however, some loss in lateral stiffness with
increasing drift.

* FRP strengthened specimens exhibited more but finer cracks than the
unstrengthened specimen.

* For lateral drifts greater than 0.5% the absorbed energy decreases in the
unstrengthened wall while it increases in the other walls. At 0.7% drift the energy
absorption capacity was 40% greater for the strengthened walls. Absorbed energy
was calculated as the area under the loading portion of the load vs. displacement
curve for each phase of loading.

Gustavo Tumialan, Nestore Galati, and Antonio Nanni (2002)

'Flexural Strengthening of Unreinforced Masonry with FRP Bars'- These

researchers investigated the behavior of four 24" wide by 48" tall by 3.75" thick initially

unreinforced hollow concrete unit specimens subjected to out of plane loading. Three

were retrofitted with varying amounts of near surface mounted (NSM) GFRP bars and

the fourth had a 3" wide strip of externally bonded GFRP laminate the height of the wall

applied. NSM involved cutting vertical grooves the height of the walls and bonding the

bars into the grooves with epoxy paste. The laminate wall reinforcement was equivalent









to the NSM wall with one bar in terms of axial stiffness (Modulus of Elasticity of GFRP

x Cross Sectional Area). Conclusions:

* Strengthening masonry walls with GFRP bars can substantially increase out-of-
plane flexural strength and pseudo-ductility.

* The original flexural capacity of masonry can be increased by 4 to 14 times. The
researchers opine that these values should be taken as reference only in walls that
can be idealized as simply supported.

* A masonry wall strengthened with NSM GFRP bars exhibited similar performance
to a wall strengthened with GFRP laminates.

A. M. Holberg and H. R. Hamilton III (2001)

'Strengthening URM with GFRP Composites and Ductile Connections' -

Researchers investigated the behavior of simulated low-rise masonry building piers

retro-fitted with FRP and discrete steel reinforcement. The FRP was added to help

resist shear and flexural stress. The steel was added to increase the ductility and lateral

load capacity of the system. Specimens were subjected to in-plane cyclic loading

applied with a hydraulic actuator.

Test specimens were four full-scale single-wythe hollow concrete unit walls laid in

running bond with full mortar bed. The GFRP laminate was formed with unidirectional

glass fiber bonded to the walls with two-part epoxy. Added steel reinforcement was of

two types, both intended to transfer uplift from the edges of the specimen to a concrete

base. One was an external system in which GFRP strips bonded to the wall were placed

under a steel angle/plate configuration which was bolted to the floor. Uplift forces in

the glass strap would induce bending in the steel plate, which was designed to yield

before failure of the strap. The other steel retrofit was no. 3 steel rebars installed inside

the blocks by removing face shells at both edges of the wall and after bar insertion

filling the cells with grout. The bar was bonded with epoxy into a hole drilled in the









concrete base. This steel was also sized to yield prior to the failure of the FRP. One

wall was not retrofitted (no. 1).

Unanticipated problems occurred which included a premature pullout of the internal

rebar from the concrete base, the failure of the FRP where it was bent around the steel

angle, and 'bottoming out' of the springs used to apply 'gravity' load. Additional

springs were later added in series. In spite of these problems useful data was obtained.

Lateral capacity was increased from 3.3 kips for no. 1, to from 5.7 to 5.9 kips for the

retrofitted specimens. The test was terminated at 0.1 % drift for no. 1 prior to what

would have been maximum drift. Retrofitted specimens reached 0.6% to 1.7%

maximum drift. All retrofitted specimens showed energy dissipated by the added steel.

This was indicated by the open hysteretic loops in the Load vs. Drift plots.

Kunwar Bajpai and Dat Duthinh (2003)

'Bending Performance of Masonry Walls Strengthened with Surface Mounted

FRP Bars' These researchers investigated the behavior of concrete masonry beams

subjected to four point bending, simulating out of plane bending of a wall. These

beams were reinforced with various amounts of FRP bars on the tensile face of the

beams. Beams were either two units wide or four units wide and 9.33 feet long. The

bars were installed in 12 inch square grooves cut into the masonry surface either parallel

or perpendicular to the mortar bed joints, one bar in a narrow beam and three in the wide

beams.

Prior to the flexural tests, bond tests were conducted on two sizes of FRP bars /2

inch and 3/8 inch diameters and three adhesive types two epoxies and one latex

modified mortar. One of the epoxies proved superior for bonding the FRP to masonry.

This adhesive was used for another set of tests, which showed that bars which were









sand-coated with a helical fiber tow achieved higher bond strengths than bars with

circular ribs on a smooth surface. It was also determined that smaller diameter bars

develop a higher bond strength relative to tensile strength. This was expected, as

smaller bars have a higher ratio of perimeter to cross sectional area than larger diameter

bars. Finally they used the higher strength epoxy in tests where the epoxy was

reinforced with 0.12 inch long glass fibers at a volume fraction of 5%. This was found

to significantly enhance the strength of the bond and allowed close to full strength

development of the 12 inch dia. bars in 7.3 inches (less than half a concrete masonry

unit length). This was the adhesive mixture used for the bending tests.

The bending tests of eight specimens four narrow and four wide found a mean

span to deflection ratio of 42.

The authors felt that full anchorage of the FRP bars was assured with their

methods and that the use of ACI 530-02 equations can be used to calculate the ultimate

flexural strength design of concrete masonry beams and walls reinforced with near-

surface mounted FRP bars.

Thanasis C. Triantafillou (1998)

'Composites: A New Possibility for the Shear Strengthening of Concrete,

Masonry and Wood' This paper reports research results related to the use of

composites as shear strengthening materials for concrete, masonry and wood members.

Presented are analytical models for the contribution of composites to the shear capacity

of strengthened elements, within the framework of ultimate limit states.

It is shown that in the case of concrete and masonry, the design of FRP

strengthened members can be treated on the basis of the classical truss analogy and by









accounting for an effective FRP strain, which depends on the product of the FRP elastic

modulus and the area fraction.

The total shear capacity, VRd, for a masonry wall of length I and thickness t,

reinforced with horizontal epoxy bonded FRP laminates with area fraction equal to Ah

(defined as the total cross sectional area of laminates divided by the corresponding area

of the wall) is given as:

VRd = VRdl + VRd2 < 0.3fktd/(M

fk characteristic compressive strength, masonry

d= effective depth (taken approximately equal to 0.81 as suggested by Paulay

and Priestly (1992) for masonry walls with several layers of reinforcement)

(M (not identified by Triantafillou but assumed to be a safety factor for masonry)

taken as 2.5 by Triantafillou for calculations.

VRdl accounts primarily for the contribution of uncracked masonry

VRd2 accounts for the effect of shear reinforcement modeled by truss anolgy

VRdl = f l '(

fk characteristic shear strength of masonry

fvk = min [fvkO + 0.4NRd//t, 0.7fvk,lim, 0.7max(0.065fb, fvkO)]

fvko characteristic shear strength of masonry under zero compressive stress. Is

between 0.1 Mpa and 0.3Mpa (The lower limit applies in the absence of

experimental data), depending on the type of masonry units and the mortar

strength.

fvk,lim = limiting value of fvk, is in the range of 1.0 MPa to 1.7 MPa, depending on

the type of masonry units and the mortar strength.









fb = normalized compressive strength of masonry units, is equal to a size factor

factor (between 0.65 1.55) times the mean compressive strength of masonry

units.

Factor 0.7 applies only in the (usual) case of seismic design

In simplified form: fyk = min (fykO + 0.4NRd//t, fvk,max)

VRd2 = AhEfrpyfrp,u/(frp)tO.9d

Efrp = Young's modulus for FRP

Yfrp,u = ultimate tensile strain FRP

(frp = partial safety factor FRP

r = reinforcement efficiency factor, depending on the exact FRP failure

mechanism (FRP debonding or tensile fracture).

Triantafillou has rewritten VRd2:

VRd2 = 0.7/(frp AhEfrpYfrp,elt

frp,e = an effective FRP strain. Expected to decrease as AhEfrp increases.

Triantafillou gives the shear capacity of masonry strengthened with FRP laminates in

final form as:

VRd/flt = (0.8/(M)min(fko/fk + O.4NRd/fklt, fvk,max/fk) + Th (0.7/(frp)(Yfrp,e/YM,u))0.25/(M

Th = (YM,uEfrp/fk)Ah

frp,e = 0.0119 0.0205(AhEfrp) + 0.0104(AhEfrp)2

Triantifillou ignores the contribution of the vertical FRP to shear capacity, justified by

assuming it only provides dowel action.

He finally demonstrates with some typical values plugged into his equations that

depending on the axial load, the increase in shear capacity due to the external









reinforcement can be considerable, and that it reaches a cut-off value at relatively low

values of Th, corresponding to low values of FRP area laminates.

0. S. Marshall and S. C. Sweeney (2002)

'In-Plane Shear Performance of Masonry Walls Strengthened With FRP' -

Researchers conducted in-plane shear tests of 4' x 4' unreinforced double-wythe brick

wall specimens and lightly reinforced single-wythe CMU wall specimens at the U.S.

Army Engineer Research and Development Center Construction Engineering Research

Laboratory. Both GFRP and CFRP laminates were tested. The laminates were applied to

one wall face only.

Conclusions:

* For low gravity loads (low rise buildings) it was discovered that the strength of the
building was increased in relation to the amount of material that crossed the failure
plane (typically the horizontal bed joint in low rise buildings). Strength increase
was not linear with amount of FRP applied.

* For high gravity loads (typically medium rise buildings) the most common form of
failure is rocking or X cracking.

* Multiple plies of FRP, particularly GFRP, do not always increase strength. Failure
of this configuration was due to delamination of the FRP from the wall. The
investigators felt this was an indication that the laminate was too stiff

* FRP composites can be applied to increase the strength and change the failure
mode of masonry walls in shear. In all cases, however, application of FRP
laminate caused a shift to a less ductile failure mode.

M. J. N. Priestly and F. Sieble, 1995

'Design of Seismic Retrofit Measures For Concrete and Masonry Structures' The

authors report that seismic repair and retrofitting of structural walls can be accomplished

very economically with thin advanced composite overlays. Tests focused on 1) reduction

of shear deformations in seismically damaged structural walls, 2) repair or retrofitting of









shear walls to achieve ductile flexural behaviour, 3) increase in flexural ductility of

structural walls, 4) retrofitting of out-of-plane unreinforced structural walls.

All tests were performed on full scale walls constructed of fully grouted hollow concrete

masonry units. Subsequent to sandblasting and filling of voids with epoxy or polymer

concrete, advanced composite overlays were applied to the wall surface either single or

double-sided in the form of mats or woven fabrics saturated with resin in and

impregnator.

Especially for in-plane wall response, the authors felt that very thin overlays (one or

two layers) can show significant seismic improvements. Forces to be transferred in the

composite overlays are limited by the laminar shear or principal tensile strength of the

existing structural wall material since the polymer resin typically has higher tensile

capacities than concrete or masonry substrates.

An overlay shear capacity, Vo, is given as:

Vo = fotid

fo = allowable overlay stress based on a maximum allowable strain of 0.004

d = effective structural wall length

t = thickness of composite overlay

For typical wall aspect ratios (height approx. = length) the above strain criterion

inherently assumes large shear deformations 0.4 % drift due to shear alone in order for

the composite overlay to become effective. Additional limitations on the total allowable

shear deformations can be imposed by reducing the allowable overlay stress level fo.

Alternatively, stiffness criteria, rather than strength criteria, can be employed in the wall

overlay design, limiting shear deformations to levels which can be expected in concrete









walls with conventional horizontal reinforcement Ash (determined based on conventional

concrete design requirements) by scaling the amount of horizontal overlay fabric Aoh

from the required horizontal reinforcement as:Aoh = AshEs/Eo

which will also ensure equal participation of the already existing conventional horizontal

wall reinforcement.

The authors report on the testing of a full-scale five story reinforced building. This

building was first tested under simulated seismic actions to failure. Subsequent to this

testing it was repaired with structural carbon overlays up to the second story of the

structural walls. The crushed wall toes were reconstructed with polymer concrete.

The load-deflection envelopes for the original and the retest show that a single layer of

carbon fabric (t = 1.25 mm, predominantly horizontal woven carbon fabric, 12 k toe AS4,

with epoxy resin matrix), applied to each side of the strucural walls with two layers in the

toe regions, contributed significantly to doubling the inelastic deformation capacity.

Measured shear deformations in the repaired wall panels were reduced to half the shear

deformations in the original test.

Chadchart Sittipunt, Sharon L. Wood, Panitan Lukkunaprasit, and Pichai
Pattararattanakul (2001)

'Cyclic Behavior of Reinforced Concrete Structural Walls with Diagonal Web

Reinforcement' These researchers reported that results from previous

investigations2'3'4'5 demonstrated that structural walls that deform primarily in shear, and

that experience large shear distortions, have a lower energy dissipation capacity than

walls that deform primarily in flexure. In addition, it was found that walls that

experience large shear distortions were more likely to fail by web crushing, which is

caused by deterioration of the compressive strength of the concrete struts in the web2









Experimental results3'4 indicated that increasing the amount of conventional vertical

and/or horizontal web reinforcement in walls that were susceptible to shear failure did not

significantly reduce the inelastic shear distortion nor did it appreciably improve the

energy dissipation capacity. Subsequent analytical studies6'7 indicated that the hysteretic

response of walls susceptible to shear failures could be improved if diagonal

reinforcement was used in the web. Diagonal web reinforcement provided a more

effective mechanism for transferring lateral forces into the foundation, resulting in lower

shear strains near the base of the wall, and improving the energy dissipation

characteristics.

This paper also reported the results of four reinforced concrete wall tests. The

purpose of the testing was to evaluate the influence of daigonal web reinforcement on the

hysteretic response. Two walls contained conventional horizontal and vertical web

reinforcement and two walls contained inclined web reinforcement. Within each type the

total amount of reinforcement was varied. Reinforcement details were representative of

construction practice in regions of low to moderate seismic risk. A single layer of web

reinforcement was used. The walls were dumbbell shaped (plan view) with the edges

(the bells) all containing the same reinforcement. They were held down at the base and

load was applied in plane to an integral concrete cap with the walls behaving as

cantilevers.

Each wall was tested until it experienced significant loss of capacity.

The walls with diagonal web reinforcement resisted higher loads than the other

two, however, the increase in strength was not significant for the walls with higher web

reinforcement ratios.









Conclusions:

* Walls with diagonal web reinforcement displayed the ability to dissipate more
energy at a given level of lateral deformation than walls with conventional web
reinforcement. Increasing the amount of diagonal web reinforcement increased the
energy dissipation capacity of the walls, whereas increasing the amount of
conventional web reinforcement did not change the energy dissipation capacity of
the walls significantly.

* Walls with diagonal web reinforcement experienced less shear distortion in the
hinging region than walls with conventional web reinforcement. Shear deformation
did increase, however, after the diagonal web reinforcement yielded. Web crushing
was not observed in walls with diagonal web reinforcement. Analytical results
indicated that part of the shear force was transferred directly to the foundation by
the diagonal reinforcement. Diagonal web reinforcement also helped reduce
inelastic shear deformation in the lower portion of the walls thereby preventing
deterioration of the concrete strength in the compression struts. The decrease in
force in the concrete struts and the decrease in inelastic shear deformation improves
the shear transfer capacity of concrete in the web and prevents web crushing.

* Increasing the amount of conventional web reinforcement did not significantly
reduce the shear deformation in the hinging regions, nor did it change the failure
mechanism. Web crushing controlled the response of both walls that contained
conventional web reinforcement. In walls with conventional web reinforcement,
lateral force was transferred to the foundation by compression in concrete struts
and dowel action in the reinforcement. Compressive strength of concrete struts
deteriorated significantly when the walls were subjected to large inelastic shear
distortions. Large shear forces in the compressive struts and deterioration of
compressive strength led to crushing of the concrete in the web.

REFERENCES

1. Paulay, T. and Priestly, M. J. N., Seismic Design of Reinforced Concrete and
Masonry Buildings. John Wiley and Sons, Inc., New York, 1992.

2. Oesterle, R. G., Aristizabal-Ochoa, J. D., Shiu, K. N. and Corley, W. G. 'Web
Crushing of Reinforced Concrete Walls'. ACI Journal, May-June, 1984.

3. Oesterle, R. G., Fiorato, A. E., Johal, L. S., Carpenter, J. E., Russel, H. G. and
Corley, W. G. 'Earthquake Resistant Structural Walls Tests of Isolated Walls'.
Report to National Science Foundation, Oct. 1976

4. Oesterle, R. G., Aristizabal-Ochoa, J. D., Fiorato, A. E., Russel, H. G. and
Corley, W. G. 'Earthquake Resistant Structural Walls Tests of Isolated Walls,
Phase II'. National Science Foundation, Oct., 1979.






49


5. Oesterle, R. G., 'Inelastic Analysis for In-Plane Strength of Reinforced Concrete
Shearwalls'. PhD dissertation, CE dept. Northwestern University, Evanston, Ill.,
June 1986.

6. Stittipunt, C., and Wood, S. L., 'Finite Element Analysis of Reinforced Concrete
Shearwalls.' Civil Engineering Studies: Structural Research Series No. 584,
University of Illinois, Urbana, Ill., Dec. 1993.

7. Stittipunt, C., and Wood, S. L., 'Influence of Web Reinforcement on the Cyclic
Response of Structural Walls,' ACI Structural Journal No.6, Nov.-Dec. 1995.














APPENDIX B
SPECIMEN CONSTRUCTION

A local mason contractor was hired to build the wall specimens. Bricks used

were grade MW 8 inch clay bricks purchased locally from Florida Rock Industries Inc

located in Gainesville FL. The mortar used was type N.

Eight test walls were built in a configuration simulating the pier of a wall located

between two windows (Figure 34).

-- --Pier






I I I

Figure 34: Illustration of specimen model

This model was chosen because of the susceptibility of this portion of a structure to

fail during an earthquake. The height of the pier is configured to be half of what it would

be in a building. This is to simulate the 'node' of a real pier. This is where the moment

due to 'S' bending, for a shear wall loaded due to an upper floor moving horizontal

relative to the lower floor, is zero.

Precast concrete lintels were used as a base for each wall after being filled with

ready mixed concrete and reinforced longitudinally with two no. 6 steel reinforcing bars.

Two holes were drilled in the lintels and tubes installed prior to the concrete pour. These

were used as lifting points for each specimen.







51



The length of the base lintels was 112 inches (2.84 m). They were used with the


precast face up to provide a flat surface for laying the bricks. Figure 35 and Figure 36


illustrate the specimen configurations.


112 in. (2.8m)


Figure 35: Specimens II VIII Tests Ih, li, 2, 4, 5, 6, 7, 8

64 in.
(1.6 m)
S 48 in. m
(1.2 m)


Pre-cast
concrete lintel



Pre-cast
concrete lintel


Lifting
holes


48 in. pier
(1.2 m)


f 16
S0.


in. base
4 m)


112 in. (2.84 m)


Figure 36: Specimen I Test 9


m









Figure 37 shows the first course of brick being laid on the base lintel.










A B

Figure 37: A Base lintel, B First course of brick being laid

The specimens were constructed in running bond with two wythes. Header courses

were located at the fourth course up from the lintel and every sixth course after that.

Collarjoints were filled solid with mortar. Figure 38 A and B shows the typical brick

and grout set-up for the base.













Figure 38: A Brick laying and B grouting

The wall 'base' was laid six bricks tall (16 inches). The pier was centered on this

base and built 48 inches wide and 48 inches tall.

Specimen I (test 9) was constructed with mortar joints such that the top course of

its base (sixth layer of bricks) had joints in line with the edges of the pier. On all other

specimens the joints in the top course of the base were offset from the edges of the pier.









Figure 39 A and B shows the bricks of a pier being laid. Figure 40 shows a header course

being laid and Figure 41 shows a completed wall sans top lintel.


Figure 39: A and B Laying pier bricks


Figure 40: Laying header course


Figure 41: Completed specimen (no top lintel)









A second pre-cast concrete lintel was placed on top of the pier. This lintel was 64

inches long (5 feet, 4 inches) and was used for attaching the concrete cap of the test

fixture.

The walls were allowed to cure for 28 days before any GFRP was applied or any

testing performed. From that time on GFRP and steel rebar (if used) were installed on

one or two specimens at a time. The prepared specimens were tested prior to determining

the GFRP/rebar configuration for the following specimens.

The location and placement of the GFRP reinforcement was chosen to provide

strengthening to areas that were susceptible to failure prior to the wall reaching a load

that would yield the steel dowels or the tension straps/glass rebar. The GFRP placed in

an 'X' across the pier was used to prevent failure due to shear. The vertical straps along

the edges of the pier were used to carry the tension load down through the brick to the

pier/base interface or down through the base for specimens with no steel. GFRP was laid

over the base to prevent bending failure there and across the top lintel/pier interface to

prevent sliding of the lintel.

The surfaces that FRP were to be applied to were wire brushed with a heavy duty

motorized rotary wire brush. After testing the first specimen it was thought that FRP

adhesion could be improved by sandblasting the brick surface. The rest of the specimens

were sandblasted and the dust removed prior to the application of the FRP. Bond tests

were later performed however and the brick substrate failed without exception whether

the surface was wire brushed or sandblasted.

SikaWrap Hex 100G was used as the glass fiber for specimens I, II, III, V, VII, and

VIII. This is a unidirectional E-glass fiber. Weight is 27 oz. per sq. yd. This material









was applied in various widths for in-plane strengthening of the pier as the vertical straps,

reinforcement for diagonal tension strengthening as the X bracing, and flexural

strengthening of the base as a strap applied along the top.

A lighter weight glass fabric with strands oriented 45 degrees in two directions was

applied as a full sheet to the base for shear strengthening and a strip across the joint

between the bricks and the top lintel to strengthen the bond between these two elements.

Both of these cloths were bonded to the walls using Sikadur 330, a high modulus two part

epoxy. This resin was applied to the wall with a paint roller. The glass was then applied

and more resin rolled onto the fabric until it was saturated or the glass was saturated first

and then applied. Excess resin and air bubbles were forced out with a squeegee. A photo

of this process is shown in Figure 42.

Specimen IV used a pre-impregnated glass cloth. This was G 15000 unidirectional

grid reinforcement from Clark Schwebel Tech-Fab Co. This material is made by bonding

E-glass fiber rovings with epoxy resin in a controlled factory environment. The adhesive

for this wall was a 'low modulus' two part trowleable epoxy from Thermal Chem.

Specimen VI had no cloth. All reinforcement was no.3 fiberglass rebar Aslan

100 GFRP. Four vertical bars were installed the full height of the wall, two at each edge

of the pier. Both bars of each pair were installed in a 3% x 3% inch groove four inches from

each edge of the wall. X bracing was installed across the pier with a bar in each of

similar grooves as well as another bar the length of the base across the top. The grooves

were cut with a circular saw with a masonry blade and were slightly deepened as

necessary to allow bars to cross each other. The bars were glued in with Concresive

1420.



















Figure 42: Applying FRP to a concrete block wall

The steel rebar, when used, was glued into a 3A inch diameter hole using Concresive

1420, a two part structural epoxy. The holes were drilled with a hammer drill starting at

the top of the 12th brick course on one side and drilling diagonally downward to emerge

at the bottom of the first course of bricks on the other side of the wall. The holes were

brushed out and then blown out with the lab shop air to remove most of the dust. The

holes were filled with epoxy using a length of tube inserted to the bottom. The tube was

withdrawn as the glue was injected. The rebar was coated with epoxy as it was inserted

into the hole. Figure 43 shows the epoxy injection system and Figure 44 A and B shows

the process of injecting the epoxy into a rebar hole.

.wEi mk


Figure 43: Epoxy injection system





























A B

Figure 44: A and B Injecting epoxy into rebar hole

Figure 45 shows an edge view of the position of an installed steel rebar. This was

typical for all specimens with steel added. All rebar was installed from the same side of

the wall.


No. 3
rebar








Figure 45: Typical steel rebar configuration














APPENDIX C
EXPERIMENTAL PROGRAM

Test Setup

The test setup was designed to load the masonry specimens in plane (Figure 46).

The inverted 'T' configuration, representing the lower half of a wall pier between two

windows, required tie-down points at each end.

A 55 kip MTS hydraulic acutuator was placed between the top of the cap and the

reaction frame. This actuator was part of a closed-loop hydraulic loading system. The

system was controlled by an MTS 407 controller. The controller used a sinusoidal

voltage output from the data acquisition system to impart the desired displacements to the

cylinder. The actuator has a built-in load cell that was used to acquire the load imposed

on the specimens during testing. Extension and retraction of this device simulated the

loading conditions that would be experienced by a shear wall during ground movement

parallel to the wall.

The ICBO Acceptance Criteria for Concrete and Reinforced and Unreinforced

Masonry Strengthening Using Fiber-Reinforced Composite Systems (ACI125) (ICBO

1997) was followed to determine the displacements to be imposed for each test. For

walls with no steel the yield point was taken as the displacement that was expected to

cause failure of an unreinforced wall. For walls with steel reinforcement yield was taken

as the displacement at which the steel was expected to yield. These yield displacements

were assigned : = 1. The displacements then imposed during testing were fractions or

multiples of:. : = /4, 1/2, 1, 2, 3, 4, 6, 8, 10, 12, 16 etc. The specimens were loaded in











displacement control with three complete cycles for each displacement level :. A


complete cycle was one displacement: in each of the positive and negative directions.


The specimens were loaded through increasing : until lateral load carrying capacity was


lost.

ALL THREAD
4 KIP/IN SPRING \ ROD
(QTY 2) 50 KIP HYDRAULIC ACTUATOR
\I \ \ REACTION FRAME
2000 # CAP



East West

ALL THREAD
ROD



CONCRETE
BASE


STRONG FLOOR
(THICK REINFORCED CONCRETE SLAB)


Figure 46: Test stand North elevation

Lateral movement out of plane of the top of the wall was prevented at the cap by


attaching a strut at each end of the cap to a frame attached to the wall of the lab (Figure


47). These struts were pinned at the ends allowing free movement in plane of the wall.


The base was a solid concrete block with longitudinal and stirrup steel


reinforcement. It was first attached to the lab floor through two cast in place holes using


three inch diameter studs threaded into sockets in the strong floor. The nuts to the studs


which held the base down were tightened as much as possible by hand with a three foot


long wrench.









South North



2 STRUTS
(ONE EACH
END OF
CAP)











Figure 47: Test stand East elevation

The specimens were lifted and moved using bridge cranes connected to a handling

fixture (see photo). This fixture consisted of a strongback, four vertical rods of

Allthread, and four angle brackets. The brackets were bolted through the bottom lintel.

The four rods were attached to the brackets and to the strongback, which was set on the

top lintel. This allowed tightening of the rods, providing some compression to the wall

during handling. The bridge crane was hooked to the strongback with a two legged sling.

A 1/2 inch high damn was built around the top edge of the base. Prior to setting

each specimen in place a layer of Hydrostone was poured onto the base. The wall was

then set into the wet Hydrostone.

The lower section of the specimen was clamped down to the base with the use of a

hydraulic jack. Small beams were used to transfer the force inboard from the location of

the holdown brackets on the base. The jack applied tension to the hold down rods by

pressing against the beams. A nut was tightened against the beam at the desired pressure

on the jack and the jack was removed from the system. The beams imparted the force









into steel plates set on the wall approximately 8 inches from the ends of the wall. The

hold down force at each end was approximately 20,000 pounds.

The cap is solid concrete with longitudinal and stirrup steel reinforcement. Four

hollow tubes were installed longitudinally. These tubes were set at the bolt pattern of the

clevis of the hydraulic ram allowing the ram to be attached to the cap with four threaded

rods running through the cap which were nutted at the far end.

A layer of mortar was placed on the top of the upper lintel and the cap was set on

the wet grout with the two side struts and the hydraulic ram being attached just prior to

the cap contacting the wall. The cap was then clamped to the lintel with threaded rod

through cross beams. The nuts to the threaded rod were tightened as much as possible by

hand using a three foot long pipe on the end of the wrench. A dial gauge was installed

between the cap and the top lintel to indicate any relative movement between the two.

None was detected during any of the tests.

Two springs (4 kips/in. stiffness) were used to maintain a near constant vertical

force on the specimen during in-plane testing. The springs were placed on a horizontal

beam that rested on the cap. A second horizontal beam was placed on top of the springs.

Two threaded rods passed through the beams and were connected to the concrete base

below the specimen. The springs were compressed 3% inches with a hydraulic jack and

nuts on the rods were tightened to hold the spring force and transfer it into the specimen.

The hydraulic pressure was released after the nuts were tightened. The springs imparted

a downward force of 6000 pounds into the specimen. Combined with the 2000 lb. weight

of the cap and the weight of the pier/lintel this provided a 'gravity load' of 9000 pounds.









With the geometry of the gravity load setup a horizontal displacement of one inch

in either direction compressed the springs 0.005 inches. This adds 40 pounds of spring

force. This does not account for spring compression due to rocking. The springs being

located in the center of the wall would experience approximately half of the uplift

expressed by Flo or Gina. This uplift typically turned out to be approximately equal to

the horizontal displacement so for a 12 inch horizontal movement the springs would

recieve a /4 inch compression. This would equate to an added vertical downward force of

2000 pounds.

Figure 48 through Figure 53 show photos of the test fixture and specimen set-up.













Figure 48: Specimen installed in test stand


Figure 49: Reaction frame

























Figure 50: Lateral movement prevention struts

7


Figure 51: Wall end of a lateral movement prevention strut





















Figure 52: One of two 'gravity' load springs












Figure 53: Specimen handling fixture

Instrumentation

Figure 54 shows the location of either the instrument itself or the attachment point

to the wall for the instrumentation that was common to all specimens. The type of each

device shown is listed in Table 8 along with what measurement was being taken. Each

device was either mounted to the wall with its probe contacting or attached to a solid

stand or the device was mounted to a stand with its probe contacting or attached to the

wall. The figure does not necessarily show the location of the instrument but the location

where the measurement is being taken. All stands were heavy and solid to the lab floor.

Carol and Diane were located as shown for several tests and then moved to the west side

(same relative location) for the remainder of the tests.









East


4+- Carol


West



Gina

Vanessa (oop)

Henry Ian



(oop out of plane)
(oop = out of plane)


Emily


Figure 54: Instrumentat locations (string and linear pots) all walls


Table 8: Instrumentation description
Name Type Measurement Shown
Carol String pot Horizontal Displacement in plane Attach point
Gina String pot Vertical Displacement in plane Attach point
Flo String pot Vertical Displacement in plane Attach point
Emily Linear pot Horizontal Displacement in plane Instrument
Diane String pot Horizontal Displacement in plane Attach point
Will Linear pot Horizontal Displacement out of plane Contact point
Vanessa Linear pot Horizontal Displacement out of plane Contact point
Ian Linear pot Vertical Displacement in plane Instrument
Henry Linear pot Vertical Displacement in plane Instrument
Karl Linear pot Vertical Displacement in plane Instrument
Jim Linear pot Vertical Displacement in plane Instrument
Linda Strain Gauge Vertical strain FRP or glass rebar
Nancy Strain Gauge Horizontal strain FRP or glass rebar
Marie Strain Gauge Vertical strain FRP or glass rebar
Oscar Strain Gauge Steel strain
Pete Strain Gauge Steel strain
Quin Strain Gauge Steel strain
Rick Strain Gauge Steel strain









Carol, Diane, Flo, and Gina were string potentiometers (BEI Duncan miniature

spring return linear motion sensors models 9610 and 9615). The string was pulled out to

the approximate halfway point before being secured to allow for positive and negative

measurements. The calibration factors were taken from the value imprinted on each

instrument. The data acquisition program measured the potentiometer supply voltage as

well as the output of the potentiometer so that and accurate linear measurement could be

computed.

The remainder of the potentiometers were calibrated using a calibration tool and a

LabVIEW developed by the researchers. The tool held the instrument while the stroke

length was measured and recorded by the LabVIEW program. The values recorded from

this process were used to calculate the calibration factor. These pots were compressed to

the approximate halfway point before being secured. This allowed positive and negative

displacement readings to be taken.

The FRP strain gauges (Texas Measurements Inc. Part no. PFL-30-11) were used

to measure fiberglass strain in the sheet FRP in the configurations shown in Figure 55 -

Figure 59 and to measure glass rebar strain for test 8 Figure 58. When used with FRP

sheet they were installed in the wet resin. When used with glass rebar they were glued to

the rebar.

The steel strain gauges (Texas Measurements Inc. Part no. FLA-5-11-1L) were

glued to the rebar before the rebar was placed in the wall and located in the center of the

bar in order to measure the strain at the pier/base interface. The locations of these gauges

are shown in Figure 56, Figure 57, Figure 59, and Figure 60. These gauges were covered

with tape and shrink wrap tubing for a length of four inches (Figure 61). This gave a four







67


inch unbonded length of the steel to the brick allowing the steel strain to be distributed

over this four inch length.


SLinda
S Nancy
I -


-Marie
(Ih, li, 6 only)


Figure 55: FRP strain gauge location Tests lh, li, 5, 6







SRick


Pete -
Oscar-
___ 1 ___


Linda
I Quin
=11 Nancy


Figure 56: FRP and steel strain gauge locations Test 4


Linda


Oscar Pete


Figure 57: FRP and steel strain gauge locations Test 7



















Figure 58: Glass rebar strain gauge locations Test 8


\\\\

Linda
Oscar
Oscar J


~I i


Figure 59: FRP and steel strain gauge locations Test 9


Oscar-


Figure 60: Steel strain gauge location Test 2


Pete


Pete























Figure 61: Steel strain gauge installation

Data Acquisition

A personal computer, National Instruments LabVIEW software, and a 16-bit data

acquisition card were used for acquiring the data.

A LabVIEW program was developed to obtain and log the measurements. On the

main screen (Figure 62), the user could specify file names for recording the data, identify

cycle number, monitor the strain gauges and view a load vs. displacement graph for the

test. The load and displacement shown on the screen are from the actuator load cell and

Linearly Variable Displacement Transducer (LVDT).

At the beginning of every test a Zero Scan was run before any specimen

displacement occurred. The Zero Scan measured the initial positions of each of the

instruments. A Regular Scan was run while the specimen was being displaced. The

Regular Scan recorded the value of the current position of an instrument minus its value

obtained from the Zero Scan. The Regular Scan value was shown on the screen.
























lu lI ll.^ |HM~.. -V ImWiai3L

Figure 62: LabVIEW program main screen

The MTS actuator was controlled by a program written in LabVIEW also (Figure

63). Input consisted of desired displacement value, frequency, and the number of cycles

to run each displacement value. The program sent a voltage output, which corresponded

to the to the particular displacement, to the MTS actuator. A calibration factor of 0.5

inches per volt output remained constant throughout the testing program.


1F, MS SignalGeneration


Figure 63: MTS Signal Generation program screen









Component Tests

Individual bricks, brick prisms, steel rebars, FRP tensile coupons, and FRP bond

samples were tested to determine the compressive strength of the bricks and prisms, the

tensile strength of the steel rebar and FRP samples, and the peel strength of the FRP bond

to brick.

Seven bricks were randomly taken from the pallet of bricks the walls were built

from. These were tested in compression to failure in a Tinius Olsen testing machine.

As each wall was being built a prism was constructed of four bricks using mortar

from the batch being used for that wall. These were also tested in compression to failure

in a Tinius Olsen machine.

Four pieces of steel rebar were chosen randomly and tested in tension in the Tinius

Olsen machine. ASTM A370 was followed for these tests.

A sheet of the Hex 100G glass cloth was saturated with the Sikadur resin and

allowed to cure. Five coupons were cut from this composite. These were cut to a length

of 14 inches and milled to an average width of 1.04 inches. Two inch long 'grab tabs' of

printed circuit board fiberglass were epoxied to both sides of each end of these coupons

for a gauge length of 10 inches. These pieces averaged 0.091 inches in thickness. These

were tested in tension in the Tinius Olsen.

The base of a tested wall was prepared for FRP bond strength tests. This involved

using the glass that was already on the base of a sandblasted wall and applying some

glass to a bare section that had been wire brushed. A coring saw was used to cut 2 inch

diameter test patches by just cutting through the fiberglass to the brick surface. 2 inch

diameter steel pucks were epoxied to these patches. After allowing everything to cure

these pucks were pulled off the wall using a James Co. bond testing device which









measured the force required to pull off the fiberglass patch. In all cases the brick

substrate failed, indicated by the entire patch being covered with brick material.

Material Properties

Table 9 Table 14provide the results from the component tests.

Table 9: Individual bricks Compressive strength
Individual Bricks

Test Compressive Stress (psi)
1 5610
2 5035
3 8635
4 8874
5 8203
6 9249
7 8891

Average 7785

Table 10: Brick prisms Compressive strength
Brick Prisms

Specimen Compressive Stress (psi)
I 4210
II 3133
III 4479
IV no results
V 3837
VI 4841
VII 4173
VIII 4925

Average 4228









Table 11: Steel rebar Tensile strength
No. 3 Steel Rebar
Test Yield Stress (ksi) Elongation
1 61 1.164
2 61 1.164
3 63 1.173
4 63 1.140

Average 62 1.160

Table 12: Glass rebar Tensile strength
FRP Tensile Coupons

Test kips/inch width Stress (ksi
1 2.80 34.2
2 3.12 32.5
3 2.53 27.0
4 2.84 32.7
2.57 26.8

Average 2.77 30.64

Table 13: FRP bond tests Wire brushed wall
FRP Bond Tests Wire Brushed Wall

Test Force (lbs.) Stress (psi)
1 2250 716
2 1425 453
3 2800 891
4 2400 764

Average 2219 706

Table 14: FRP bond tests Sand blasted wall
FRP Bond Tests Sand Blasted Wall

Test Force (lbs.) Stress (psi)
1 2600 828
2 2750 875
3 2200 700

Average 2516 801


(%)









The James Bond tester applies the force perpendicular to the surface of the FRP

and pulls uniformly over the surface of the patch. The above results indicate the tensile

properties of the brick. All that can be deduced about the bond strength of the FRP to

brick perpendicular to the plane of the FRP is that it is stronger than the tensile capacity

of brick. Of course this is all that is necessary for an application such as wall

rehabilitation.

These bond strengths were not seen for every wall tested. When separation of the

FRP from the brick occurred without brick failure it is assumed that this was due to a

'peeling' action (pulling from an edge), which is going to be a different strength than that

tested by the James Bond tester. An admittedly non-scientific test was performed where

several strips of the glass cloth were stuck to brick surfaces that were either wire brushed

or sand blasted. Resin was applied and the strip bonded to the brick only for a two inch

length leaving a 'handle'. These strips were pulled from the brick surfaces by hand in a

peeling action. The bond to the sand blasted surfaces was noticeably stronger than the

bond to the wire brushed surfaces although no numbers for this bond strength were

measured.

Aslan 100 GFRP rebar This material was not tested as a component. The

strength given by company literature for a no. 3 bar is 110 ksi. With a cross sectional

area of 0.131 sq. inches this gives a tensile strength of 14.41 kips for a bar of this size.

Pre-impregnated FRP This material was not tested but is specified as having a

tensile strength of 1.2 kips per inch width of fabric.















APPENDIX D
SPECIMEN DETAILS AND RESULTS


Brick test Ih

Specimen ID: III

Date of Testing:
August 21, 2002

Date of Construction:
5/2/02

Date of FRP Application:
7/29/02

Conditions during FRP Application:
Temp: 90F
RH: 60%

Conditions during Testing:
Temp: 80F
RH: 78%

Material Properties:

FRP Test Coupons tensile strength:
Results (avg.) 30.64 ksi 2.77 kips/inch width

FRP/Resin Pulloff tests
Results: Brick failure, 700 psi to 890 psi

Brick Prisms
Results (avg.) 4.23 ksi

Brick
Results (avg.) 7.79 ksi

Failure Mode:
Pier Rocking










Description of Failure: Vertical FRP peeled away from the brick at Pier/Base interface,
debond progressing from interface and moving up incrementally with each displacement
cycle.
The bond of the FRP to brick was inadequate to allow tensile reinforcement failure across
the pier/base interface. Debonding probably occurred due to out of plane movement of
wall.
Table 15 and Figure 64 and Figure 65 describe and show the location of the FRP.

Table 15: FRP description- test lh

Description of FRP Reinforcement
Test Ih Specimen III
Direction Area Width Length
IDn. (in.) (in.
A Unidirectional .042 3 68
B Unidirectional .084 6 112
C +-45 deg 18 112
D Unidirectional .042 3 68
E +- 45 deg 12 48
Resin Sikadur Hex 300.
Glass SikaWrap Hex 100G


Figure 64: FRP layup -North side



E A (2 PL)

DC


Figure 65: FRP layup South side


` ` ` ` ` `







77


Table 15 and Figure 66 show crack circumstances and locations.


Table 16: Crack occurrence


Figure 66: Crack pattern at failure


Figure 67 and Figure 68 show photos of specimen Ih.


B I1


Figure 67: A North side. B South side


Crack Occurrence Test Ih

Location Span Ram LVDT (in.)


1 0.17 3


2 0.23 4


i-~i-~i





























Figure 68: Progression of glass debondin



Figure 69 shows plots of the data for spe





20

10

0 I I
o
0
-10

-20


-1 0 1
Displacement


Displacement (in.)


78




















ig (black lines)



cimen lh.


20 89


10 44.5


0 0
0
o _

-10 --44.5


-20 -89
2 -2 -1 0 1 2
Drift (%)


40000
w

-J

2 20000
L,

0 0.


1 -1 1
Displacement (in.)


-2




5000

~2500
z

S 0
C,
w-2500
LL.

-5000
-1













20000


10000


0


-10000


-20000


0.1


E -0.1


-0.2


-0.3
-0




0.3

0.2

0.1

0.0

-0.1

-0.2
_n3


0

Displacement (in.)


1


0.5


0 I I


0.5


-1
-1 -0.5 0 0.5 1
Displacement (in.)















.5 0.0 0.5
Displacement








-0.5-0.0


-v .
-0.5 0.0
Displacement



Figure 69: Data reduction plots


-1 -0.5 0 0.5 1
Displacement (in.)


0.1


C-0.1


-0.2


-0.3
-0




0.3

0.2

0.1

S0.0

-0.1

-0.2

-0.3
-0


1.5


Displacement


1.5 0.
Displacement


0
C
14-

"5 -
0









Brick test li

Specimen ID: III

Date of Testing:
8/23/02

Date of Construction:
5/2/02

Date of FRP Application:
8/22/02

Conditions during FRP Application:
Temp: 90F
RH: 60%

Conditions during Testing:
Temp: 80F
RH: 78%

Material Properties:

FRP Test Coupons tensile strength:
Results Not Applicable

FRP/Resin Pulloff tests
Results: Brick failure, 700 psi to 890 psi

Brick Prisms
Results 4.23 ksi

Brick
Results 7.79 ksi


Failure Mode:
Pier Rocking/FRP tensile failure at sill
Description of Failure: Spray-on FRP began cracking at the pier/base interface on the
east edge of the west strip Cracking began at 0.12 inches ram displacement. Cracking
of FRP continued up the east edge of strip as displacement increased culminating in
rupture across the strip approximately 12 inches above pier/base interface.










Comments: Test specimen III was tested in test Ih. After completion of test Ih spray on
chopped fiberglass was sprayed onto wall on the opposite side from the laid up vertical
FRP. Each edge received a vertical strip of spray on FRP from bottom of base to top of
pier, 4 inches in from edge. Dimensions: approx. 8 inches wide x approx. 5 mm thick
measured at sill line. 2 inch fiber length. Vinyl Ester resin.

Table 17 and Figure 70 show FRP description and location

Table 17: FRP description Test li


Description of FRP Reinforcement
Test li Specimen III
Direction Area Width Length
ID (in.2 (in.) (in.
A Unidirectional .042 3 68
B Unidirectional .084 6 112

C +-45deg 18 112
D Unidirectional .042 3 68
E +- 45 deg 12 48

F random 1.6 8 64
2 in. fiber length sprayed on

Resin Vinyl Ester for spray-on. Sikadur Hex 300 for played up.
Glass 2 inch chopped for spray-on. SikaWrap Hex 100G for
played up.




E / A (2 PL)



C
B B


K


Figure 70: A Spray on/ FRP layup North side. B FRP layup South side


F


C


K>






82


Table 18 and Figure 71 show crack occurrence and location

Table 18: Crack occurrence Test li


Figure 71: Crack pattern at failure


Figure 72 and Figure 73 show photos of test li.


Figure 72: Overall view North side


Crack Occurrence Test li
Crack in specimen occurred during testing of specimen in test lh.





























Figure 73: Tear in FRP


Figure 74 shows the data reduction plots.


20
15
10
S5
0
0 -5
-10
-15
-20


-2 -1 0
Displacement


-:
0







0.1

0.0

S-0.1

-0.2

-0.3


1 2


3.5

0 II

3.5

-1
-1 -0.5 0 0.5 1
Displacement (in.)














-1 0 1
Displacement (in.)


-2 -1 0
Drift (%)


0.1

0.0

=-0.1

-0.2

-0.3


89


44.5


0
0
-1
-44.5


-89


1 2


0
Displacement (in.)









0.1
0.0
-0.1
-0.2
-0.3


_______________f________________
-1 0


-1 0
Displacement (in.)
Figure 74: Data reduction plots


0.1
0.0

.,
-0.2
-0.3


0
Displacement (in.)









Brick test 2

Specimen ID: VIII

Date of Testing:
12/03/02

Date of Construction:
5/28/02

Date of FRP Application:
11/14/02

Conditions during FRP Application:
Temp: 67F
RH: 58%

Conditions during Testing:
Temp: 73 deg. F
RH: 50 %

Material Properties:

FRP Test Coupons tensile strength:
Results 30.64 ksi 2.7 kips/inch width

FRP/Resin Pulloff tests
Results: Brick failure, 700 psi to 890 psi

Brick Prisms
Results 4.23 ksi

Brick
Results 7.79 ksi

Failure Mode: Diagonal Tension, Pier Rocking.

Description of Failure: Wall cracked diagonally above one rebar and vertically/slight
diagonal next to the other one. It cracked across the base of the pier and across the wall
at the top of the rebar. Some delamination of FRP occurred at base of pier. FRP that
came loose had pieces of brick stuck to it. Sliding is indicated by the 'lower' loops in the
Load vs. Displacement and the plot of Diane vs. Displacement. First steel yield is
indicated at the -0.064 displacement blip in the Load vs. Displacement and is confirmed
by the enlargement of the Steel Strain Pete plot. Steel stretched and took a lot of set as
shown on Steel Strain Oscar.










Table 19 and Figure 75 show FRP description and layup
Table 19: FRP description test 2

Description of FRP Reinforcement
Test 2 Specimen VIII
Direction Area Width Length
IDn. (in.) (in.)
A Unidirectional .028 2 48
B Unidirectional .084 6 112

C +-45deg 18 112
D Unidirectional .042 3 68
E +- 45 deg 12 48

Resin supplied by Sika


A (2 PL) E


NO. 3 REBAR
(2 PL)


C


D
B


B


Figure 75: A FRP layup North side. B FRP layup South side


A (2 PL)


K


-










Table 20 and Figure 76 show crack occurrence and location.

Table 20: Crack occurrence Test 2
Crack Occurrence Test 2

Location Span Ram LVDT (in.)

1 0.064 1

2 0.128 2

3 0.256 4

4 0.384 6

5 0.512 8

6 0.768 12

7 1.024 16


4
6
-5 -L-S --- S I3


A 2' 3 2 B 5- 2

Figure 76: Crack pattern at failure A North side, B South side

Figure 77 Figure 79 show photos of test 2.


5 -6