RECTANGULAR BEAMS 



105 



considerable. Even in the case assumed in Fig. 49, at least one 

 stirrup should be employed in this distance, as shown. 



45. Points to Bend Horizontal Reinforcement. If some of the 

 horizontal bars are bent -up at a given point to provide for 

 diagonal tension, those remaining should have sufficient sectional 

 area to carry the tension beyond this point. 



R (i- x 2 orD x/AlIi) 2 



M" 2~ orR-M p- 



L 



L ; 



FIG. 50. 



In determining the horizontal length of the various bars neces- 

 sary to resist the bending moment, the same method, as developed 

 by Messrs. Taylor and Thompson in " Concrete, Plain and Rein- 

 forced/' 1 may be used as in the design of plate girder flanges. 

 Consider uniform loading. 



Let m = number of bars actually required for moment at 



the center of the beam. 

 w 2 = number of these bars to be bent. 

 I = span of beam in feet. 



wl 2 

 M = maximum moment -^-> in which 



o 



x 2 = distance from support to point where m 2 bars may 

 be bent up leaving sufficient steel to carry the 

 tension. 



The ratio of stress at the center of the beam to that at the 

 point under consideration equals the ratio of moments at these 

 points. Thus, if the steel is stressed equally at both points, 



M X2 :M= (m m 2 )(area of one bar) :w(area of one bar). 

 Substituting 



w 



=-g- and 



8 2 



From Taylor and Thompson's "Concrete, Plain and Reinforced,' 

 Copyright, 1905, 1909, by Frederick W. Taylor. 



2nd edition, page 458. 



