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FARM BUILDINGS IN SOUTH AFRICA 



bars may be spaced twice as far apart as at the bottom, i.e. 12" apart, while at 

 £ height they may be four times as far apart or 24" from centre to centre. 

 For practical reasons, however, they are kept closer together, as shown in 

 Fig. 166. 



The vertical bars in the wall may be looked upon as stress distribution rods, 

 inserted for the purpose of transmitting the stresses in the concrete to the 

 horizontal hoops ; they should be inside the hoops. 



Design of Reinforced Concrete Tank or Reservoir (Figs. 179-184). 



Each wall of the tank consists of a slab supported at intermediate points by 

 the piers, and at the ends by two of the other walls. The slab may be con- 

 sidered to be continuous, like a continuous beam. We will first consider 

 a strip of the slab, 1 foot in height, at the bottom of the tank. Fig. 216 is a 

 cross section of this strip under consideration. 



By Hooke's law — 



stress 



E 



(I.) 



-UlU- 



_l_.^L^ 



Fig. 216. 



strain 



Let / c denote the safe compressive 

 stress in the concrete = 500 

 lbs. per sq. in. 



ft denote the safe tensile stress 

 in the steel = 16,000 lbs. per 

 sq. in. 



E c denote the modulus of elas- 

 ticity for concrete. 



E t denote the modulus of elas- 

 ticity for steel. 



Then 



E* 



E 



, may be taken = 15. 



From equation I., 

 for the concrete, 

 for the steel, 



strain = 



stress 

 ~E~ 



f 



strain, = -~ 

 E 



strain* =•£ 



strain. 



/c/E c _/c E, 

 *E C 



strain* f t /E t ft 

 But strain is proportional to distance from the neutral axis, hence — 

 strain c h 



(II.) 



straint d — h 



(see Fig. 216) (III.) 



