84 STANDARD SPECIFICATIONS 



40 per cent of their strength at the yield point, as determined 

 by tests. 



350. Maximum Stresses. When combining the temperature 

 stresses with stresses due to all other causes, the specified unit 

 stresses (Pars. 348, 349) may be increased 10 per cent, provided 

 that this combination gives a greater sectional area. 



DESIGN OF STRUCTURE 



351. General Proportions: 



(a) The total thickness of a slab shall not be less than one- 



thirty-sixth (^g-) of the slab span in the direction of 

 the principal reinforcement, or less than 3 in. 



(b) The minimum width of web, in beams or girders, shall 



not be less than one-twenty-fourth (^) of the span. 

 (Par. 342.) 



(c) The maximum diameter of reinforcing rods, in slabs, 



beams or girders, shall not exceed one-two-hundredth 



Orb) of the s P an - 



352. Continuous Spans. Where continuity of spans, or 



fixed ends, are depended upon and allowed for in determining 

 the bending moment at center, the slab or beam must be properly 

 reinforced over the supports to resist the negative moment. 



353. Bond Strength. Ends of plain reinforcing bars must 

 be secured against slipping, either by depending upon the bond, 

 In which case the length of the free end shall be not less than 

 48 diams. of the rod, or by bending the free end through 

 180 to a radius of 4 diams. of rod, or by an anchorage con- 

 sisting of the free end being upset and provided with a nut and 

 a washer. The free ends of stirrups may, at points where the 

 beam has no top reinforcement, be turned closely through 

 approximately 360 for this purpose. At points where top 

 reinforcement exists the free ends of the stirrups shall pass 

 over the same before being so turned, or shall be wound around 

 the bars approximately one and one-half (1) turns. 



354. Web Reinforcement. After deducting the shear or 

 diagonal tension carried by the concrete (Par. 348d, 348e) the 

 remainder shall be carried by reinforcement consisting of bent 

 rods or stirrups, or both. The stirrups shall be properly secured 

 against slipping. (Par. 353.) 



