Experimental Investigation of Pullout Behavior of Fiber-Reinforced Polymer Reinforcements in Sand

Abstract

Fiber-reinforced polymer (FRP) bars and strips are potential alternatives to conventional soil reinforcements. In this aspect, two commonly used FRP materials are glass-FRP and carbon-FRP (GFRP and CFRP). However, the differences in pullout behavior between soil-embedded GFRP and CFRP rods, and conventional steel bars, are not well understood. This paper describes the results of an experimental study that was conducted to investigate the behavior of FRP bar/strip-sand interfaces under low normal pressure. A series of pullout tests were performed on GFRP and CFRP bars and strips buried in sand. A simple model using the ideal elastoplastic interface shear stress-strain relationship is proposed to simulate the pullout behavior of the FRP reinforcements. The progressive pullout process and the evolution of interface shear stress distribution are obtained from the proposed model. The experimental and analytical results show that, in comparison with CFRP and steel reinforcements, the GFRP reinforcement has a more nonlinear and nonuniform distribution of interface shear stress, and the pullout is more progressive. The differences in Young’s modulus and interface shear coefficient lead to the different pullout behaviors of these three materials. The reduced Young’s modulus gives GFRP reinforcements a risk of excessive tensile elongation and bending deflection. The test results show that the progressive pullout behavior is also governed by the reinforcement dimensions.