SLABS, CROSS-BEAMS, AND GIRDERS 145 



notes flange-width, not web-width, and p (the steel ratio) is 



not & (Fi - 73 - } 



Case II. The Neutral Axis in the Web. The amount of com- 

 pression in the web (aaaa, Fig. 73) is commonly small compared 

 with that in the flange, and is generally neglected. The method 

 of procedure in determining formulas for " moment calculations" 

 of T-beams is identical with that for rectangular beams and the 

 resulting equations only will be given. 



The formulas to use, assuming a straight line variation of 

 stress and neglecting the compression in the web, are: 



k = 



1 



(1) 



kd = 



2nda 8 +bt 2 . 

 2na s +2bt 



k = 



_3kd-2t I 

 Z ~2kd-t 3 



. 



J 



-* 



M r = 



M 



a s jd 



: _f^_ 



n(l-k) t 



(2) 



(3) 



(4) 

 (5) 



(6) 



(7) 

 (8) 



Approximate formulas can also be obtained. From the stress 

 diagram, Fig. 73, it is clear that the arm of the resisting couple 

 is never as small as d l/2t, and that the average unit compressive 

 stress is never as small as l/2/ c , except when the neutral axis is at 



