CORRUGATED BAR COMPANY, 



Floor Slabs Supported Along Four Sides. Floor slabs having the supports 

 extending along the four sides should be designed and reinforced as continuous over 

 the supports. If the length of the slab exceeds 1.5 times its width the entire load should 

 be carried by transverse reinforcement. 



For uniformity distributed loads on square slabs, one-half the live and dead load 

 may be used in the calculations of moment to be resisted in each direction. For oblong 

 slabs, the length of which is not greater than one and one-half times their width, the 

 moment to be resisted by the transverse reinforcement may be found by using a pro- 

 portion of the live and dead load equal to that given by the formula r = r —0.5, where 







Z = length and 6 = breadth of slab. The longitudinal reinforcement should then be 

 proportioned to carry the remainder of the load. 



In placing reinforcement in such slabs account may well be taken of the fact that 

 the bending moment is greater near the center of the slab than near the edges. 

 For this purpose two-thirds of the previously calculated moments may be 

 assumed as carried by the center half of the slab and one-third by the outside 

 quarters. 



Loads carried to beams by slabs which are reinforced in two directions will not be 

 uniformly distributed to the supporting beams and the distribution will depend on 

 the relative stiffness of the slab and the supporting beams. The distribution which 

 may be expected ordinarily is a variation of the load in the beam in accordance with 

 the ordinates of a parabola, having its vertex at the middle of the span. For any 

 given design, the probable distribution should be ascertained and the moments in the 

 beam calculated accordingly. 



Continuous Beams and Slabs. When the beam or slab is continuous over its 

 supports, reinforcement should be fully provided at points of negative moment, and 

 the stresses in concrete recommended in the section on "Working Stresses," should 

 not be exceeded. In computing the positive and negative moments in beams and slabs 

 continuous over several supports, due to uniformly distributed loads, the following 

 rules are recommended: 



(a) For floor slabs the bending moments at center and at support should be taken 



at-j-o for both dead and live loads, where w represents the load per linear unit and I 

 the span length. 



(b) For beams the bending moment at center and at support for interior spans 

 should be taken at -r^ and for end spans it should be taken at -jr: for center and 

 interior support, for both dead and live loads. 



(c) In the case of beams and slabs continuous for two spans only, with their ends 

 restrained, the bending moment both at the central support and near the middle of 



the span should be taken at -r^ • 



(d) At the ends of continuous beams the amount of negative moment which will be 

 developed in the beam will depend on the condition of restraint or fixedness, and this 

 will depend on the form of construction used. In the ordinary cases a moment of 



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