USETUL DATA 



On Diagram 1 find the intersection of /i:=123.5 and p = 1.22 and read/, = 11,900, 

 /c = 650. On the upper portion of the diagram for p = 1 . 22 find j=0. 846 and A: = . 452. 



T-Beams. In the design and investigation of T-beams Diagrams 2, 3 and 4, pages 

 17, 18 and 19 will be found useful. These diagrams apply only when the neutral axis 

 falls below the under side of the flange of the T-beam. When the neutral axis falls 

 above, the diagrams for rectangular beams apply. 



Diagram 2 can be used only when the area of steel is such that/, is 16,000 and Dia- 

 gram 3 wlien /s is 18,000. From these diagrams, for any assumed value of d and for 

 fixed values of M, t and b, we may obtain j for determining the steel area required and 

 also the value of /c. If /c is fixed, knowing M and t, we may find the value of 6 or d, 

 by assuming one of them, and obtain the corresponding steel area. It should be borne 

 in mind that 6 must not exceed code or specification limits. 



Diagram 4 gives values of k and j for T-beams and is useful in checking steel and 

 concrete stresses, the dimensions and reinforcement being known. 



Example 1. Given a T-beam having a span of 24 feet, freely supported, to carry 

 a total load of 2,000 lb. per foot, t=5 in., 6 = 30 in., /. = 16,000, /c = 650, n = 15, p=120. 



^^(2,000K2|(24)a2) = 1.728.000 in. lb. 



r=»M =24.000 lb. 

 Assuming a width of stem of 10 in. we find from shear considerations, 

 i=\,= ^r 22.85 in. 



(120) Q (10) 



From Diagram 2 trace upward from the value of ^ =0.219 to intersection with the 



M 

 curve f or /c = 650 and read 7^= 92.0. Substituting for Jf and d the values given 

 oar 



above we find 



1,728,000 _ 

 (6) (22.85) (22.85) 

 & = 35.8in. 

 This exceeds the fixed dimension of 30 in. for 6 so that it becomes necessary to 

 assume a new value for d. Try d = 26 in. 



then y =0.192 

 a 



and from Diagram 2 



6 = 29.7 in. 



This value is sufficiently close so as to require no further revision. 



To find the area of steel required first obtain j from the right-hand side of Diagram 



M 

 2 by tracmg upward from /o = 650 to intersection of r^ = 86.0 and read j= 0.913 



11 



