Theory of Cracking in Concrete Members

A theory is presented which predicts the crack width and crack spacing in the constant moment region of a reinforced or prestressed beam. The theory is based on the same assumptions as the classical theory of cracking for reinforced concrete. Instead, however, of assuming a bond stress distribution, the bond slip characteristic of the steel is used and this results in the bond distribution continually changing as the steel stress increases. The theory is used to investigate the effect of a variation of the main parameters on the crack width and crack spacing of theoretical tensile specimens reinforced with strand and deformed bar. It is shown that, for a given steel stress at cracks, the crack width depends mainly on the maximum bond strength of the reinforcement and the crack spacing depends mainly on parameters Ψ and m, the tensile strength of the concrete, and the maximum bond strength of the reinforcement.