SLAB, BEAM, AND COLUMN TABLES 191 



8. A continuous T-beam, uniformly loaded, has a bending moment at 

 the center of each span of 358,000 in.-lb. Negative bending moment at the 

 supports and the positive bending moment at the center of span are figured 



by the formula, M = ^ The tensile steel at the center of span consists of 

 four 3/4 in. round rods. 6' =9 in. d =15.5 in. Design the supports. 



Two of the tensile rods on each side of the supports will be bent up and 

 made to lap over the top of the supports, while the other two rods on each 

 side will be continued straight and lapped over supports at the bottom of 

 beam. 



The ratios of steel in tension and compression are the same, and are 

 respectively: 



(1.77 in above computations taken from Table 13.) We will assume 



, =0.1 as before. 

 a 



From Table 11, Part 2, knowing p'=p, we obtain 



for p =0.015 ' 



Thus, 



for p =0.013 



Maximum pressure in concrete is 



358,000 



f* = (9) (15~5) a (0 291) = per sc l uare mch - 



Also, 



'- ""S^-l^D 



9. The effective area of a column is 144 sq. in. ; load to be carried is 80,000 

 b.; and working stress on the concrete is 450 lb. per square inch. What 

 percentage of longitudinal bars without hooping will be required? Take 

 n =15. 



The safe strength of a plain concrete column would be 



144 X 450 = 64,800 lb. 

 Hence, 



P 80 1 9 

 F'-64*" 1>235 



From Table 12, for n =15, and p =0.017 



-, = 1.238 



Thus, 1.7 per cent of steel is required, and 



A 8 =(144) (0.017) =2.45 sq. in. 



From Table 13, four 7/8-in. round rods will be seen to have about the 

 required area. 



