166 CONSOLIDATED STEEL CORPORATION 



The greatest safe load may be limited by the safe shearing or crippling 

 strength of the web, which should be investigated. The shear due to the load 

 W is a maximum at the point a under the outer edge of the superimposed 

 load, and is found as follows: 



V s = maximum shear due to the load W. 



V greatest safe allowable shear on web of beam. 



v __^W(L-N) 



The shear F 8 must not exceed V, the safe shearing strength of the web. 

 If the beams are thoroughly imbedded in concrete and the webs prevented 

 from buckling, 



V= 12,000dl = safe allowable shear, in pounds. 



But if the webs are not supported against buckling, 



1Z,OOOdt _ / safe crippling strength of 

 web, in pounds, 



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

 flanges, all in inches. The last formula is that for the safe crippling strength 

 of webs and values for it are given for Bethlehem Beam and Girder Sections 

 in the tables on pages 128 and 129. 



When shearing strength of the web is considered, the maximum load on a 

 given grillage beam is 



and the safe shearing strength required by the web of a beam for a given 

 loading is 



To find the safe load on a given beam use formulas (1) and (3) and take 

 the lesser of the two values. When formula (3) gives the smaller value the 

 safe load is limited by the shearing strength of the web. 



To select a grillage beam for a given loading find the coefficient of strength 

 required by formula (2) and the safe shearing strength of web required by 

 formula (4). The proper beam must then be selected to satisfy both require- 

 ments. 



It will be found that Bethlehem Girder Beams are desirable and economical 

 for use as grillage beams. 



