Function of Steel as Reinforcement in Concrete

Steel is a high-strength material compared to concrete. The useful strength of ordinary reinforcing steel in tension as well in compression, i.e. the yield strength, is of the order of 10 times the compression strength of common structural concrete, or of the order of 100 times its tensile strength. On the other hand, steel is a high-cost material as compared with concrete.

The two materials are best used in combination if the concrete is made to resist the compression stresses. Thus, in reinforced-concrete beams the resists the compression force, longitudinal steel bars are located close to the tension face to resist the tension force, and frequently additional steel are disposed that they resist the inclined tension stresses which are caused by the shear force in the webs of beams.

 

However, reinforcement is also used for resisting compression forces primarily where it is desired to reduce the cross-sectional dimension of compression members, as in the lower floor columns of multistory buildings. Even such necessity is not exist, a minimum amount of reinforcement is placed in all compression members to safeguard them against the effects of small accidental bending moments which might crack and even fail an unreinforced member.