Time-Dependent Tension-Stiffening Mechanics of Fiber-Reinforced and Ultra-High-Performance Fiber-Reinforced Concrete

Abstract

The tension-stiffening behavior of fiber-reinforced concrete is of fundamental importance for the characterization of crack widths and spacings as well as determination of the tensile response of fiber-reinforced concrete members with internal reinforcement. In this paper, a model is presented for the tension-stiffening behavior of strain-softening and strain-hardening fiber-reinforced and ultra-high-performance fiber-reinforced concrete with an allowance for the long-term creep and shrinkage effects of the concrete. Closed-form analytical solutions are derived to describe the crack spacings and load slip behavior assuming either a simplified linear ascending bond stress–slip relationship or a more realistic bond stress–slip relationship from the literature. Further, it is shown for design how the stiffness of the reinforcement can be characterized using an effective modular ratio, which can easily be incorporated into member analysis techniques to characterize the serviceability behavior of flexural members. Finally, the results are validated against a broad range of fiber-reinforced concretes of normal, high, and ultra-high strength, thus demonstrating validity for a wide range of different fiber-reinforced concretes (FRCs).