ALLOWABLE STRESSES IN REINFORCED CONCRETE. 521 



old, under laboratory conditions of manufacture and storage, the mixture being of the same con- 



as is used in the field. 



Lb. per 

 K\. In. 



Structural steel in tension 14,000 



High carbon steel in tension 17,000 



Steel in compression, 15 times the compressive stress in the surrounding concrete. 



Concrete in bearing where the surface is at least twice the loaded area 700 



I'oiirri-u- in direct compression, without reinforcement on lengths not exceeding 6 times 



the K-ast width 450 



Concrete in direct compression with not less than i per cent nor over 4 per cent longitudinal 



reinforcement on lengths not exceeding 12 times the least width 450 



Concrete in compression, on extreme fiber in cross bending 750 



Concrete in shear, uncombined with tension or compression in the concrete 120 



Concrete in shear, where the shearing stress is used as a measure of the web stress 40 



Note. The limit of shearing stresses in the concrete, even when thoroughly reinforced 



for shear and diagonal tension, should not exceed 120 



Bond for plain bars 80 



Bond for drawn wire 40 



Bond for deformed bars, depending on the form 100-150 



The following working stresses have been recommended by the Committee on Concrete and 

 Reinforced Concrete of the American Society of Civil Engineers, Proceedings, vol. XXXIX, 



February, 1913. 



Per cent of com- Lb. per 



press! ve strength sq. in. 



Structural steel in tension 16,000 



Concrete in compression where the surface is at least twice the loaded area 32.5 

 Concrete for concentric compression on a plain concrete column or pier, the 



length of which does not exceed 12 diameters 22.5 



Compression on columns with longitudinal reinforcement only, to the 

 extent of not less than I per cent and not more than 4 per cent; the 



length of the column shall not exceed 12 diameters 22.5 



Compression on columns with reinforcement of bands, hoops or spirals 

 having not less than I per cent of the volume of the column, the clear 

 spacing of the hooping to be not greater than one-sixth of the diameter 

 of the encased column and preferably not greater than one-tenth, and 

 in no case more than 2\ in., the ratio of the unsupported length of 



column to diameter of hooped core to be not more than 8 27 



Compression on columns reinforced with not less than I per cent and not 



more than 4 per cent of longitudinal bars and with bands, hoops or 



spirals as above specified, where the ratio of unsupported length of 



column to diameter of hooped core is not more than 8 32.625 



Compression on extreme fiber of a beam, calculated for constant modulus 

 of elasticity (stresses adjacent of the supports of continuous beams 



may be 15 per cent higher) 32.5 



Shear in beams with horizontal reinforcement or without reinforcement ... 2 

 Shear in beams thoroughly reinforced with web reinforcement (the web 

 reinforcement exclusive of bent-up bars to be designed to resist two- 

 thirds the external shear) 6 



Shear in beams reinforced with bent-up bars, only 3 



Punching shear, only 6 



Bond stress between concrete and plain reinforcing bars 4 



Bond stress between concrete and drawn wire 2 



The modulus of elasticity to be taken for the design as follows: 



(a) One-fifteenth that of steel where the strength of the concrete is taken as 2200 Ib. per sq. in., 



or less. 



(b) One-twelfth that of steel where the strength of the concrete is taken greater than 2200 Ib. 



per sq. in. or less than 2900 Ib. per sq. in. 



(c) One-tenth that of steel where the strength of concrete is taken as greater than 2900 Ib. 



per sq. in. 

 In calculating deflection take one-eighth of the modulus of elasticity of steel. 



