APPENDIX I 



Calculation of Horizontal Reinforcing Bars (Hoops) in "Wall 



of Silo 



The silo (Fig. 166) is 15 feet diameter by 30 feet high, internally. 



For a depth of silage of 30 feet, the pressure on the silo wall at the bottom 

 is 330 lbs. per sq. ft. 



Considering a section of the wall 1 foot high at the bottom of the silo, 

 the bursting pressure which is resisted by the sections pq and rs (Fig. 215) 

 = 330 X 15, the internal diameter of 

 the silo being 15 feet. "We design so 

 that the reinforcement alone will be 

 strong enough to take this stress with 

 safety, i.e. we neglect the tensile 

 strength of the concrete. The above 

 bursting pressure is divided equally 

 between the two sections pq and rs. 



.-. Total stress on section pq (or rs) 



33o X 15 



2475 lbs. 



Allowing a safe stress in the iron of 

 12,000 lbs. per sq. in., and denoting 

 the cross-sectional area of iron in the 

 lowest foot of the silo wall by A sq. ins., we have — 



12,000 A = 2475 

 2475 



Fig. 215. 



A 12,000 



A = 0-206 sq. in. 



Now the cross-sectional area of a §" round bar is 0"11 sq. in., hence two 

 f" dia. bars, in the lowest foot of height of the wall, will be sufficient ; i.e. the 

 horizontal reinforcement at the foot of the silo wall should consist of |" dia. 

 bars (hoops), spaced 6" apart vertically from centre to centre. 



Theoretically the §" reinforcing bars may be spaced further apart, the nearer 

 they are situated to the top of the silo. Thus at mid-height these horizontal 



