Tension Stiffening Behavior of Ultrahigh-Performance and Normal-Strength Concrete Reinforced with GFRP and Metallic Reinforcement

Abstract

This paper experimentally evaluates the tension stiffening response and cracking behavior of ultrahigh-performance concrete (UHPC) ties reinforced with glass fiber–reinforced polymer (GFRP), steel, and titanium bars under direct tension and compares their response with those of normal-strength concrete (NSC) specimens. The influence of GFRP bar surface type on the tension-stiffening behavior of NSC is also evaluated. Fiber-optic sensors are used to measure strain distributions along the specimens, and digital image correlation is employed to determine crack evolution and width. Results show that UHPC ties exhibit strain-hardening behavior after cracking, whereas NSC ties exhibit softening. A comparison of GFRP bar surface types indicates that surface type has no significant influence on the mechanical performance of the concrete ties, including restrained shrinkage behavior and cracking load. Existing models proposed for predicting the elastic modulus and cracking strength of reinforced NSC and UHPC concrete are shown to be in good agreement with the test results. A modified version of an existing model is proposed to predict the behavior of GFRP-reinforced UHPC ties in tension. Modeling results demonstrate that the proposed model can predict the behavior of GFRP-reinforced UHPC ties to within 5% of the experimental results on average.