F = 2 * 4770 ■*■ 3 = 3180 pounds, which is close enough for this 

 preliminary trial 



Lateral Force 



Fj = 12 * A = 410 pounds, A of the foundation is negligible (1) 

 d l 1 



F. = W , * tan i = 4770 * tan 2° = 167 pounds (3) 

 l sub 



Checking lateral load 



F. = F J < 1/2 * W . (4) 

 l d — sub 



577 _< 2385, which is satisfactory 



Checking for keys 



F = 0.1 * W , = 477 pounds (5) 

 h sub 



F. + F = 577 > 477, therefore keys are required 

 d = ,17 + 0.05 * B = 0.57 feet (6) 



Overturning 



Assuming the base of the structure is 2 feet above the plane of 

 the footings, 



z = 3.5 feet 



z = 3.1 feet 

 csw 



M = z T * F, + z * F. = 1550 foot-pounds (7) 



d L d csw l 



Placing the centers of the footings at the corners of the structure 

 platform gives, 



r . =5.8 feet 

 mm 



F = 1/3 * W , + M^, -i r . = 1930 pounds (8) 

 sub d mm 



Numbers in parentheses reference the applicable equation from preceeding 

 sections . 



19 



