3^0. In the above eqiiationsj S^ is given by the sum of all forces above 

 G or 



Sq=f^-t (123: 



= ii9li5 - T (see equation 115) 

 and the moment M„ is 



u 



^C — 



M « -fi (TIG - 1) - CG X T (12U: 



G -"- 



i|^^ (9«36 - 2,82) »f9,36 T 



= 32,300 - 9.36 T (See equation 99 and 

 In addition, h^^ = 2»36 feet (equation 98) 



Po = 505 pounds per square foot (equation 96) 



R = 21U pounds per square foot per foot of depth (equation 97) 



P7 = po Rj Z, I Rj = 26e7 pounds per square foot per foot of depth 

 ^1 U 1 U (equation lOi*) 



- -h^ - 



2R, S, 



and 7 = ^8 " ^ ' ^^ (equation 105) 



ana l^ = —^ — 



Rhn^ 

 where S„ = S^ J— = (h9U5 - T) - 595 = li350 - T (equation 12: 



therefore Z^ = 505 - x/T5057^ - 53 ol^ (1;350 -"t)' 



26,7 



= 18»9 - V 32o3 + 0,075 T 



351. For optimum design the maximum bending moments should be equal. The 

 exact solution of the equation M„ = M^ is difficult, and it is best solved by 



trial and error, assuming for the first trial M„ = 0„ Then 



