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IEAIPINI STR1[NfThl 0f W4(11[ AT ANCL[ TV TUC 1RAIN No. 1203 IRevised March 1956 ,'  i U DEPOSITORY HUME LIBRARY Ocr i, 1972 F.A.S. jiv. of Floni.a" * = FOES PRDUT LABORATOR FO ES SERVICE* MADION 5 WISONSI I' 1111 BEARING STRENGTH OF WOOD AT ANGLE TO THE GRAINI By Forest Products Laboratory,2 Forest Service U. S. Department of Agriculture The compressive strength of wood depends on the direction of the grain with respect to the direction of the applied force. It is highest parallel to the grain and lowest perpendicular to the grain, and for other angles has intermediate values. The ratio between the values perpendicular and parallel to the grain are not the same for different species of wood and also vary with the method of applying the load. For example, the basic stress of Douglasfir is 1,450 pounds per square inch parallel to the grain and 2355 pounds perpendicular to the grain, while for oak these respective values are 1,550 and 3565. The safe load on a 1inch bolt in a 6inch Douglasfir timber is 5,840 pounds parallel to the grain and 2,440 pounds perpendicular to the grain. On account of this variation in the magnitude and relationship of the compressive strength parallel and perpendicular to the grain, the determination of the proper value for intervening angles has always been a difficult problem in timber design. To present values in tables for all the conditions would be impracticable. The bearing values for inter vening angles, therefore, are usually obtained from the values parallel and perpendicular to the grain by the use of the Hankinson formula. This, however, involves a separate calculation for each individual condition and in order to provide a more convenient method the accompanying nomo graph, based on the formula, has been developed by John A. Scholten of the U. S. Forest Products Laboratory. The nomograph is based on the Hankinson formula, which is considered most applicable by the U. S. Forest Products Laboratory. By means of this nomograph the stress or load for any intervening angle can be obtained from the stress or load parallel and perpendicular to the grain without any calculation. The symbols in the chart are represented 1 Original report by J. A. Newlin, Specialist in the Mechanics of Wood, published in Engineering NewsRecord May 11, 19359. Maintained at Madison, Wis., in cooperation with the University of Wisconsin. AgricultureMadison Rept. No. 1203 1 by allowable loads or stresses, but the formula is applicable for loads or Btrsr..i1, generally. The intercepts on any vertical line are pro portional to sin2Q from 0 to 90 degrees. The scale of the chart was ch'uL'ri primarily for convenient use with bolt loads, but for greater or lesser VLlues8 or for different units, the m.:initude of the scale can be ,.]just',d to obtain greater accuracy without affecting the chart's applicability. Rept. rNo. 1203 2 1.4 >, LEGEND S/P= ALLOWABLE LOAD OR STRESS PARALLEL TO GRAIN. 0=ALLOWABLE LOAD OR STRESS PERPENDICULAR TO GRAIN. N=ALLOWABLE LOAD OR STRESS AT INCLINATION 0 WITHi THE DIRECTION OF GRAIN. C) E M EXAMPLE: GIVEN: P, AN ALLOWABLE BOLT LOAD PARALLEL TO / GRAIN =6,000 POUNDS, 0, AN ALLOWABLE LOAD J PERPENDICULAR TO GRAIN = 2,000 POUNDS. ,, /REQUIRED: N, AN ALLOWABLE LOAD AT AN ANGLE /"" OF 40 *TO GRAIN. / SOLUTION: CONNECT WITH A STRAIGHT LINE 6,00O POULN/S ON OX(a) WIVTH THE INTERSECTION ON OYKb) OF A // /VERTICAL LINE THROUGH Z7OOO POUNDS. THE POINT WHERE / THIS LINE (ab) INTERSECTS THE LINE REPRESENTING S"" \THE GIVEN ANGLE 40, IS DIRECTLY ABOVE THE .... tlLLOkW,.: BOLT LOAD, 3285 POUNDS. ...... / yFTHE CHART IS A GRAPHICAL SOLUTION y/ / ^  .,^^ ~OF THE HANKINSON FORMULA: N P r/N + ,Q Cos z 1,000 2,000 3,000 4,000 5,000 6,000 7,000 9,000 9,000 .. "3. ALLOWABLE LOAD OR STRESS FOR P, 0, & N SCHOLTEN NOMOGRAPH FOR DETERMINING BEARING STRENGTH OF WOOD AT VARIOUS ANGLES TO THE GRAIN (REPRODUCED BY PERMISSION OF THE FOREST PRODUCTS LABORATORY) Z V 34670 F UNIVERSITY OF FLORIDA 3 1262 08927 4285 4 I 