Low and high cycle fatigue behavior of concrete-filled composite tubes

Use of concrete-filled fiber-reinforced polymers (FRP) tubes (CFFT) for columns and piles has been studied extensively over the last decade. The focus, however, has been exclusively on the short-term monotonic or static behavior of such hybrid systems. The present study reviews the low and high cycle fatigue of CFFT members. A number of test parameters were considered as follows. characteristics of the FRP tube in terms of thickness and lay-up, type and level of cyclic loading, end restraints, and presence of internal steel reinforcement. The study compares the fatigue life as well as energy dissipation of the CFFT with conventional structural columns and piles. Test results revealed that fatigue behavior of CFFT is primarily dominated by the behavior of FRP. Matrix composition and fiber architecture have a greater effect on the fatigue life and performance of CFFT. Significant stiffness reduction was observed irrespective of the type of laminate considered in the present investigation. The study indicates that, with proper design of the FRP laminate architecture and even without any internal steel reinforcement, it is likely to achieve superior fatigue performance than their reinforced concrete counterparts. In addition, it is also possible to develop adequate ductility and dissipate considerable energy in CFFT members at levels quite comparable to their reinforced concrete companions.