CORRUGATED BAR COMPANY, INC. 



To obtain the minimum concrete unit stress we know that the minimum is as much 

 below the average as the maximum is above. In this example the average concrete unit 



stress is ., „. . „. ' , . . .. = 394 lb. per sq in. Thus the minimum unit stress is 



ijtj- ^l(J^o^ Uo-) 4J -j- {loj (,4; 



394— («6— 394) =^^ pounds per square inch. 



Case II. Tension on iRe Cross-Section. Suppose the column of Case I had 



an applied moment of 800,000 in. lb. in addition to an axial load of 100,000 lb. Then 



_M _ 800,000 _ „. 



"^^ ~ JF 100,000 " ^ '°' 



f = A = o.444 



As before po=1.23% entering Diagram 7 with -j = 0.444, tracing vertically to 



Po=l-23%, then to the left margin, A; =0.60. Now entering Diagram 8a with this 

 value of k and tracing to po=l. 23%, the value of F is found to be 0. 139. Then 

 -_ , M 800,000 _„_ , 



Max./c= ^,= (0.139) (18) (18) (18) = ^^^ ^"""^^ P^^ ^^- ^°- 



This resulting fibre stress is larger than is usually permitted and would necessitate 

 a redesign of the column section in order to reduce the stress to the limit allowable. 



14 



