CONSOLIDATED STEEL CORPORATION 27 



These coefficients of strength afford a simple means of finding the safe 

 uniformly distributed load for any beam. Divide the coefficient given for the 

 beam by the length of the span in feet. The quotient is the safe uniformly 

 distributed load in pounds, including the weight of the beam. 



To select a beam to support, a given load on a given span, find the coeffi- 

 cient of strength required and refer to the. tables for a beam having a coefficient 

 of that value. The coefficient required is found by multiplying the uniformly 

 distributed load in pounds by the span in feet. 



If the load is concentrated at the center of the span the safe load is one- 

 half the safe uniformly distributed load for the. same span. To select a beam 

 for supporting a load concentrated at the center of the span, multiply the given 

 load by 2 and consider the result as a uniform load. 



If the load is not uniformly distributed or not concentrated at the center of 

 span, the bending moment must be employed. The moment of resistence of 

 the beam, in foot-pounds, must be equal to the bending moment of the loading 

 in foot-pounds. Moments of resistance, in foot-pounds, for Bethlehem I-Beams 

 and Girder Beams are given on pages 34-35 and 46-47. 



In selecting the proper beam required to support a given loading the 

 section modulus may also be used. The section modulus required is found by 

 dividing the bending moment of the loading, in inch-pounds, by the allowable 

 fiber stress in pounds per square inch. 



The maximum fiber stress, in pounds per square inch, in a beam supporting 

 a given loading is found by div iding .the bending moment produced by the 

 loading, in inch-pounds, by the section modulus of the beam. 



In the case of very short spans, or of heavy concentrated loads, the crippling 

 strength of the web may limit the safe allowable load on a beam or determine 

 the selection of a beam for supporting a given loading. The tables on pages 

 128 and 129 give the maximum safe shear on the webs, calculated by the 

 customary formula for that purpose, as explained on page 127. 



