226 Kansas Academy of Science. 



the rod is 1| inches above the bottom of the concrete? The re- 

 sistance of concrete to tensile stresses is neglected. fgi=700, Ee= 

 3,600,000, Es= 29,000,000." 



Following is the author's solution of the problem : 



"From equation (JS) we have 



8.06 64.89X0.36 , 16.11^^ ,._ 

 ^=-i:^X^-^ + \' re + -^0.6x14.5 



= -1.209 + V1.46+35. 04 = 4.883" 

 "From equation (19) we get 



and from equation (20) 



Is = 93.45x0.6- 56.07. 



"Since all the tensile stresses are carried by the steel, and all the 

 compressive stresses by the concrete, and since the tensile stresses 

 must balance the compressive stresses to fulfil the conditions of 

 stability, we have c = s = 0.5, and from equation (i^) we obtain 



T.^ 150.52X700 ,o/-rMA- 1 1 „ 



" = 4.833X0.5 =*^''^^-^ inch-pounds." 



This solution is correct up to the words, "we have c=s = 0.5." 



This conclusion does not in general follow from the statement 

 preceding it. It will follow when v=%x, and only then ; for, if 

 the stresses in tension and compression are equal, their lever arms 

 must be equal in order to produce equal moments. The tensile 

 stress is evidently applied at a distance of v from the neutral axis. 

 The compressive stress increases from at the neutral axis to fc^ 

 at a distance x from the axis. So its point of application must be 

 at a distance of %x from the neutral axis. This condition does not 

 obtain in this case. 



Further, we should obtain the same moment from the use of 

 equation (11) as from equation (li). 



