Bond clause proposals for FRP bars/rods in concrete based on CEB/FIP Model Code 90. Part 1: Design bond stress for FRP reinforcing bars

Abstract

The bond clauses in the CEB/FIP Model Code 1990 (MC90) were written for steel reinforcement in concrete. Since then, fibre reinforced polymer (FRP) reinforcing bars have been introduced as an alternative. Reinforcing steel is a homogeneous material; FRP reinforcements, however, are made of a combination of different materials with various shapes. All these FRPs perform differently under different conditions. For example, in severe environments, where steel is not durable, FRPs may perform well. To make use of fibre composites, it is necessary to bring these materials into codes of practice and the easiest way is to adapt the code clauses for steel reinforced concrete to FRP reinforced concrete. The clauses should include boxed values open for individual coefficients of different FRPs. The necessary coefficients for the code models should be determined using systems of appropriate and coupled test methods. This paper covers a code proposal for the design bond stress. Proposals for the design lengths and tension stiffening code clauses will be presented separately.