162 REINFORCED CONCRETE CONSTRUCTION 



more than a sufficient number of rods are thus run out to the 

 third point, and with the bent rods being added gradually to 

 this number until all the rods are acting in this manner at the 

 support, it is clear that this method of design is satisfactory 

 even when the bond stress at the support is the maximum 

 allowable. 



Rods should be bent in a position to take as much diagonal 

 tension as possible, usually at an angle of 45 degrees, and the 

 points where the rods are no longer needed at the bottom of 

 beam to resist tension may be found for uniform loading by the 

 formula (see Art. 45). 



x 2 = or < 



It is also necessary to determine where the rods over supports 

 may be bent down. It will be on the safe side, and sufficiently 

 accurate, to consider the curve for negative moment as a straight 

 line between the support and the point of zero moment at the 

 third point. With this variation of the moment in mind, it is 

 an easy matter to find where the rods may be bent down at the 

 top of the beam. The designer must use his judgment in the 

 matter, but this much may be said: if a 45 degree angle bend 

 cannot be made in a rod, as proposed, due to the controlling 

 points for bending at the top and bottom, a greater number of 

 rods should be employed at the center of span in order to make 

 this bending possible, and the design governed accordingly. It 

 is evident from the above that it will not always be possible to 

 place the rods so as to take all the diagonal tension; in fact, 

 there will be less likelihood than in a simply supported beam. 

 It will be advantageous in any case, however, due to the danger- 

 ous section for diagonal tension being near the support, to employ 

 some stirrups even when they are not theoretically necessary. 

 In Volume II will be given a design of a floor system illustrating 

 continuous beam design for uniform loads as well as for concen- 

 trated loads due to beams running into girders. 



Since a T-beam in the center of span becomes a rectangular 

 beam over supports, the stress in the tensile steel at the support 

 will generally be greater in ordinary designing than the corre- 

 sponding stress at the center of beam; that is, this stress will be 

 greater if half the rods are bent up on each side and lap over the 

 support. For this reason, then, When selecting the steel at the 

 center of span, a little more than the required amount at that 



