Fatigue bond behavior of glass fiber reinforced polymer bars with varying confinement levels

Abstract

This study investigates the fatigue bond behavior between GFRP bars and concrete under actual stress conditions using beam-end tests for the first time. The influence of lateral confinement provided by the concrete cover and stirrups on the fatigue bond behavior of GFRP bars was also considered. The observed failure mode of the bonding interface between GFRP bars and concrete revealed that under high-stress fatigue loading, the ribs of the GFRP bar displayed more severe shearing and smoothness compared to specimens under monotonic loading. This wear was particularly evident in specimens with greater lateral confinement levels, aligning with the crack propagation observations. The fatigue bond life between GFRP bars and concrete can be divided into three stages, with the duration of each stage being affected by the level of lateral confinement. Fatigue loading has little effect on the bond strength and peak slip of the specimens but significantly increases the bond stiffness. The proposed simplified model accurately predicts bond-slip behavior and can estimate the service life between GFRP bars and concrete. This study provides a theoretical foundation for the design and research of GFRP-RC infrastructure subjected to repeat stresses, such as highway bridge decks, airport pavements, or railway ties.