70 REINFORCED CONCRETE CONSTRUCTION 



approximately as shown in Fig. 36. In any given case the 

 exact arrangement must depend upon the nature of the loading, 

 concentrated loads tending to extend the region of large shear 

 to greater distances from the supports. Some horizontal rods 

 should be carried to the end of the beam in order to keep the 

 tension in the concrete low and reduce the tendency to the forma- 

 tion of inclined cracks. Also, if some of the horizontal rods are 

 bent up to take the place of inclined stirrups, the bends should 

 be made somewhat beyond the theoretical points required for 

 bending moment, so that the actual working stresses in the 

 horizontal steel near the end of the beam will be low. 



The method of reinforcement indicated in Fig. 36 cannot, how- 

 ever, be conveniently used in practice. Often the horizontal 







t t 



FIG. 36. 



rods are too few in number to bend up at the required number 

 of points for thorough web reinforcement, and besides it is not 

 convenient to handle rods with various inclinations at their ends. 

 The common practice is to use bent rods (all bent at the same 

 angle) combined with vertical stirrups. It should be clear that 

 rods bent at a moderate angle are well suited for sections toward 

 the center of beam, and vertical stirrups for sections near the end 

 where the steel must be spaced closer together and at greater 

 inclinations. Sometimes separate inclined reinforcement (called 

 inclined stirrups) is used and in such a case there is danger 

 of its slipping along the horizontal rods if the inclination is too 

 great. If attached to the horizontal rods, however, such rein- 

 forcement is very effective. Special forms of bars may be used, 

 such as the well-known Kahn bar, in which strips are sheared 

 from the main bar and bent up. Fig. 37 will give the student an 

 idea of some of the more common forms of beam reinforcement. 

 A discussion of this kind would not be complete without some 

 comparison being made between vertical stirrups and inclined 

 rods in regard to their effectiveness in preventing inclined tension 

 failure. To assist the student in seeing clearly the relation 



