144 STRENGTH OF MATERIALS 



where /' and e' refer to the equivalent homogeneous section as 

 explained above, and this section is taken through the center of 

 the plate. 



Similarly, from Article 120, the maximum stress in a uniformly 

 loaded, non-homogeneous, square plate of side 2 a is given by the 



formula 



V2 wa*e' . 



(93) P = ~"~H r ' 



and, from Article 121, the maximum stress in a uniformly loaded, non- 

 homogeneous, rectangular plate of sides 2 a and 2 b by the formula 



abwce' 



(94) P = -gjr 



in which e' and /' refer to the equivalent homogeneous section obtained 

 from a diagonal section of the plate. 



Problem 146. A concrete-steel floor panel is 18 ft. long, 16 ft. wide, and 4 in. 



thick, and is reenforced by square wrou^lit-in.n rods 1 in. thick, placed ; ..f an 

 inch from the bottom of the slab and spaced 1 ft. apart. Kind the maximum stress 

 in the panel under a total live and dead load of 160 Ib./t 



NOTE. Take a diagonal section of the panel and calculate the equivalent homogeneous 

 section corresponding to it. Then find the position of the neutral axis of this equivalent 

 homogeneous section, and its moment of inertia about this neutral axis, as explain- ! in 

 Article 48. The maximum stress can then be obtained from formula ? ( 



Problem 147. Design a floor panel 14 ft. square, to be made of reenforced 



concrete and to sustain a total uniform load of 120 lb./ft. 2 with a facto: 

 of 4. 



