STEEL REINFORCEMENT 



263 



FIG. 8 



U Bars. In Fig. 8 is shown a section of U bar that can 

 be used to advantage in reinforced-concrete construction 

 either as a tension or as a compression member, 

 being particularly efficient for the latter pur- 

 pose. These bars are rolled from high elastic- 

 limit steel, and are in some instances made from 

 reroUed steel rails. They are i, A. I. and \ in. 

 in thickness, weigh from 3 to 9 Ib. per ft., and can be ob- 

 tained in lengths up to 60 ft. 



Structural Shapes Used as Steel Reinforcement. The usual 

 rolled-steel structural shapes have been used extensively for 

 reinforced-concrete construction. They have an advantage 

 in that they can be readily obtained. Structural shapes 

 as metallic reinforcement for concrete work are being super- 

 seded by either plain or deformed rolled bars. One advan- 

 tage of the use of structural shapes is that a rigid framework 

 can be built up, after the manner of skeleton construction, 

 though of much lighter section, and the concrete then filled 



in around it. 



Expanded Metal. 

 Among the earlier 

 forms of metallic 

 reinforcement for 

 concrete is the dis- 

 torted steel plate 

 known as expanded 

 metal, a familiar il- 

 lustration of which 

 is shown in Fig. 9 

 (a). This form 

 of reinforcement is 

 manufactured by 

 partly shearing a 

 sheet of steel in 



parallel rows, as shown in Fig. 9 (6), and then pulling the ma- 

 terial sidewise, thus forming a diamond mesh. In this way, 

 the area of a sheet is increased about eight times, with a cor- 

 responding decrease in weight per unit area and without any 

 waste of material. The steel from which expanded metal is 



