CONSOLIDATED STEEL CORPORATION 127 



MAXIMUM SAFE SHEAR ON THE WEBS 

 OF BEAMS AND GIRDERS 



On relatively short spans the safe strength of the web of the beam against, 

 crippling, caused by the shearing stress, may determine the maximum safe 

 load which the beam should support. 



The shearing stresses in the web of a beam may be resolved into two com- 

 ponent stresses of equal intensity, at right angles to each other, and at angles 

 of 45 degrees with the neutral axis. Both of these stresses are of the same 

 intensity and equal to that of the vertical shear: These component stresses 

 are equivalent to compressive and tensile forces acting upon the web of the 

 beam. The compressive forces tend to buckle the web, but it is not entirely 

 free to buckle because the tensile forces acting at right angles have the effect 

 of stiffening it. 



The formula in general use for determining the maximum safe shear on 

 the webs of beams and girders is as follows: 



12,000 dt 



Maximum safe shear in pounds = 



h2 



SOOOt^ 



where d = depth of beam, / = thickness of web, and h = clear distance between 

 flanges, all dimensions in inches. 



The safe shears on the webs of Bethlehem Beams and Girders, derived from 

 this formula, are given in the tables on pages 128 and 129, and also the cor- 

 responding minimum spans for the greatest safe uniformly distributed loads. 



The safe uniformly distributed load for any span less than the minimum 

 span given must not exceed twice the safe shear. The safe load concentrated at 

 the center of a span must not be greater than twice the safe shear given, and 

 the corresponding minimum span will be one-half the minimum span given in 

 the table. Loading of any kind must not produce a shear exceeding the safe 

 shear given unless the webs are stiffened. 



In general, the shearing strength of the webs will be found ample for all 

 ordinary cases of loading. 



