Title: BSI newsletter
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00089446/00005
 Material Information
Title: BSI newsletter
Physical Description: Serial
Language: English
Creator: Bridge Software Institute. University of Florida.
Publisher: Bridge Software Institute. University of Florida.
Place of Publication: Gainesville, Fla.
Publication Date: Fall 2009
 Record Information
Bibliographic ID: UF00089446
Volume ID: VID00005
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.


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Bridge Software Institute

Welcome to the latest issue of the BSI Newsletter
In this issue's Technical Corner we discuss dynamic relaxation as computed in FB-MultiPler

The articles Technical Comer and Discussions are open for input from all readers If you have a topic that you think should be discussed, let us know Did you create a great model with
features that you want to share? Everyone is welcome to submit articles for possible inclusion in subsequent issues Please contact BSI at BSI@ce ufl edu with your ideas

What's New at BSI

We are pleased to announce the release of FB-MultiPler v4 13 and FB-Deep v2 02 These programs are available for download from the BSI website The new versions contain fixes to the
latest reported bugs and also include a number of new features

Technical Comer

Michael Davidson ew
Ph D Candidate, University of Florida B

New Dynamic Relaxation feature in FB-MultiPier I

When permanent loads are abruptly applied to bridge structures, dynamically amplified displacements and internal forces are generated Instantaneous application of permanent loads, nl
however, can lead to unduly amplified structural response The dynamic relaxation feature in FB-MultiPler prevents unwarranted amplification (Figure 1) Here, load effects associated with v.
permanent loads are initialized in the dynamic analysis by means of a static pre analysis Meaning, two distinct analyses are conducted a static analysis (with only permanent loads applied),
and a dynamic analysis (with all loads applied) Statically, once the structure reaches equilibrium, the stiffness matrix and displacement vector are stored These response quantities are then
used to define the initial state for the dynamic analysis Dynamically, permanent loads are imposed instantaneously, however, because permanent load stresses are already present, the abrupt
loading does not cause unrealistic vertical oscillations

Fig 1 Dynamic Relaxation Concept

A demonstration case is presented to illustrate the effectiveness of the dynamic relaxation feature as a means of obtaininmmg proper displacements when permanent loads are incorporated into a
dynamic model The model shown min Figure 1 was analyzed with self weight loadming (a permanent load) using three methods static analysis, dynamic analysis with relaxation, and dynamic
analysis without relaxation The predictions of vertical displacement at the center of the pier cap from the central pier (node 5 min the model) are shown min Figure 2b Note that the vertical
displacement histories are good agreement only between the static and dynamc-with-relaxation analyses

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(b) Comparison of analysis results

Figure 2 Three-pier bridge model subject to permanent loads a) Structural configuration, b) Central pier, center pile cap (node 5) vertical displacement

An additional demonstration case is presented to illustrate the importance of using dynamic relaxation for the purpose of accurately determining maximum structural demand The model shown in
Figure 3 was analyzed with self weight loading (a permanent load) and an externally applied lateral load (a transient load, shown in Figure 3b) using dynamic analysis with relaxation and
dynamic analysis without relaxation Structural response is compared for the two analysis types (Figure 3c), where predictions of maximum pile axial force are given for the central pier The
dynamic analysis without relaxation predicts a maximum pile axial force 20% greater than that predicted when dynamic relaxation is employed If used for pile member design, such unduly
amplified internal forces can lead to substantially greater construction costs that are unnecessary Clearly, the dynamic relaxation feature should be employed to facilitate proper application of
permanent loads in dynamic analyses

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Figure 3 3-pier bridge model subject to permanent and transient loads a) Structural configuration, b) Transient load-uhstory, c) Maximum pile axial force

Discussions with...

Henry BollmannP E
Research Engineer, Bridge Software Institute

Pile To Pile Cap Connection

The "pinned" or "fixed" condition does not always adequately represent the pile to pile cap connectivity of an actual bridge substructure Modeling both the flexural resistance and rigidity of the
connection is important to the overall structural resistance and behavior of the foundation

(a) Dead load only


Fig. 4

"Almost" any connection condition can be modeled with FB-MultiPier because the program allows for the modeling of multiple cross-sections (Fig 4) and user defined
stress-strain curves for material properties (Fig 5a). If "full section properties" are specified then the program will account for second order effects, concrete cracking,
steel yielding and the resulting changes in stiffness. One can also obtain an elastic solution as the program computes the elastic stiffness properties if the "linear" option is
selected. There are usually multiple approaches to modeling a pile connection detail.

A typical problem encountered is modeling the fixity/capacity condition of a pretensioned pile that may not be embedded deep enough into a cap to assume full bending
capacity of the pile. The section shown in (fig 5b) represents a 30 inch square prestressed pile with void concrete filled and reinforced with mild steel. The prestressing steel
has been reduced in quantity from the standard to just 16 strands, in order to account for the lack of strand development near the member end. Based upon the pile embedment
the engineer may, by trial and error, adjust material parameters until the desired strength interaction curve is achieved (fig 5c).


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Pile section lengths and node number selection must be coordinated so that a pile section contains at least two nodes.

(c) moment-interaction diagram


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Cary Peterson
Tech Support, Bridge Software Institute

Technical support questions.

When requesting technical support for any BSI software, it is recommended to email the input file ( in file for FB-MultiPler and Atlas or spc file for FB-Deep) to the BSI address bsi@ce ufl edu
along with a brief explanation and any supporting documentation of the issue This will allow the support staff to provide the users prompt tech support

Checking program version.

It is important that users have the current most up to date version of the BSI software Thus we recommend that users regularly visit the home page of the BSI website BSI To check current
version of program installed on the computer, open the program and go to Help > About to see the version number you currently have

BSI Program Status

FB-MultiPier V4 13 Download a FREE demo toda v
Released November 24, 2009 Continuing Development Technical Support Available

FB-MultiPler is the successor to FB-Pier In addition to all the capabilities of FB-Pier the FB-MultlPler program allows for the modeling of a bridge that consists of multiple piers that are connected with
bndge spans In addition to the multiple load cases and the AASHTO coefficients that are available m FB-Pier, the new program is capable of performing dynamic analysis for the bndge For more
information about FB-MultiPler, click here

SFB-Deep V2 02 Download a FREE demo todavl
Released December 12, 2009 Continuing Development Technical Support Available

The FB-Deep computer program is a Windows based program used to estimate the static axial capacity of drilled shafts and dnven piles The methodology is based upon Federal Highway Administration
(FHWA) reports FB-Deep guides the user through pile and shaft matenals data, shape and dimensional inputs, soil properties, and bonng log info FB-Deep presents the data analysis m both clear graphical
and text form For more information about FB-Deep, click here

Atlas V6 02
I Released September 24, 2009 Limited Web Support Available
Atlas is a fimte element analysis program that is used for the design/analysis of cable supported traffic signal systems The Atlas program models dual cable supported systems including single-point or two-
point attachments and suspended box systems For more information about Atlas, click here

Contact BSI

If you need to contact BSI for any reason you can use any of the methods below
Online bsi ce ufl edu
Email bsi(dce ufl edu
Fax (352) 392-3697

Mailng Address
Bndge Software Institute
University of Flonda
PO Box 116580
Gainesville, FL 32611

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