Fatigue Modeling of Concrete-Filled Fiber-Reinforced Polymer Tubes

Abstract

Field applications and laboratory research have shown the feasibility of concrete-filled fiber-reinforced polymer (FRP) tube (CFFT) in bridges. Yet, their widespread applications require developing appropriate design and analysis tools for different types of loading, particularly fatigue loads. An analytical tool is developed to trace the response of CFFTs under fatigue loading. The FRP material models are calibrated against fatigue and creep coupon tests. Material models are cast into a fiber element analysis, with an algorithm to simulate strain profile, moment-curvature and residual bending strength at any given time or after any number of fatigue cycles in a single or multiple stages of loading. Comparisons with available test data show good agreement with model predictions. A detailed parametric study shows that fatigue response of CFFT beams can improve by either increasing the reinforcement index or the effective modulus of FRP tube in the longitudinal direction. Higher load ranges may drastically reduce fatigue life. Therefore, it is important to limit the load level on CFFTs for a reliable and predictable member performance. The study also recommends reducing fiber orientation in angle plies with respect to the axis of the beam to improve fatigue performance of the CFFT member.