Need for Fracture Behavior based Designer Friendly Expressions for Fracture Energy and Minimum Flexural Reinforcement

Abstract

Present National and International codes of practice lead to a size invariant expression for minimum percentage of flexural reinforcement. But the influence of member size or fracture parameters namely, fracture energy and critical crack tip opening displacement are not considered. ACI 446.1R-91 (Re-approved 1999) strongly recommends application of fracture mechanics principles to quasi-brittle material like concrete. Detailed literature study is made on the influence of fracture energy, critical crack tip opening displacement, size of the member, compressive strength of concrete and yield strength of concrete on minimum flexural reinforcement of concrete members. Several researchers have proposed expressions for minimum flexural reinforcement of concrete members, but the review of literature on fracture behavior of lightly reinforced concrete members show contradiction in conclusions.  Designer friendly expressions for fracture energy and minimum flexural reinforcement are essential to the practicing engineers to evaluate fracture energy and minimum flexural reinforcement without knowing about the RILEM standards.