STEEL REINFORCEMENT 269 



SYSTEMS OF STEEL REINFORCEMENT 



LOOSE-ROD SYSTEMS 



A complete floor system constructed of loose rods is shown 

 in Fig. 1. The beam reinforcement consists of three rein- 

 forcing rods. Two of these rods run straight through the 

 entire length of the beam, as at a, while the third one is bent 

 upwards at the ends, as at b. This bent member provides 

 tensile resistance at the top of the beams and thus takes 

 care of the negative bending moment, which occurs in all 

 beams fixed at the end. The bend in such rods is usually 

 made at an angle of about 30 with the horizontal. The 

 rods should be straight at the center of the span for at least 

 one-third the distance between the supports. 



A tie-rod c that is 4 or 5 ft. in length, and sometimes bent 

 down at the ends, should be placed over the top of the beam 

 juncture. 



The girder reinforcement consists of five rods, two of them 

 being bent up, as shown at e, to provide against negative 

 bending moment. 



In the best work, two short rods'/ are located transversely 

 through the column. These rods tie the adjoining girders 

 together and provide additional rigidity at the junction of 

 the girders with the column. 



The slab rods, shown at h, are generally spaced at about 

 6 inches from center to center. They should bond with the 

 stirrups, or web reinforcement, of the beams, and may be 

 threaded through, interlocked, or wired to them. It is 

 customary to provide shrinkage rods that extend at right 

 angles to the regular slab reinforcement, in order to prevent 

 shrinkage cracks in the concrete. For this purpose, J-in. 

 round or square rods j are generally used, and these are 

 spaced about 2 ft. from center to center. In order to bond 

 the concrete over the main girders securely, it is also good 

 practice to provide over these important members rods d 

 of about the same size as the slab rods. These rods should 

 run through holes punched in the top of the stirrup, as 



