Damage Performance Of Concrete Pipe Pile Under Earthquake

Concrete filled steel tube pile (CFT Pile) as a form of combination design are becoming more widely used in structural applications due to the fact that higher compressive strength and favorable ductile performance is achieved through composite action. To investigate the seismic behavior of CFT pile members, numerous cyclic tests have been carried out in the past decade. Nearly all of them are based on standard loading protocols to obtain the cyclic capacity without considering the effects of earthquake and number of cycles on damage accumulation. In this dissertation, the primary focus is on earthquake effects and the cumulative damage of CFT pile under simulated seismic loading is studied and numerical simulation in detail.The simulation results show that CFT pile exhibit stable hysteresis behavior and energy-dissipation capacity. There is no seriously degradation in stiffness, strength, and ductility for CFTP designed with code even under large plastic deformation. But for CFT pile under cyclic loading with constant amplitude, degradation in hysteresis curves under larger lateral deformation become more quickly, and energy-dissipation capacity decreases too. It proves that larger deformation at CFT pile exerts more damage on it and reveals that the maximum strain of steel tube reaching fracture state is much lower than that of same kind of steel under monotonic test. The reason is that cyclic tension and comparison stress on steel tube have exerted fatigue damage on it. As damage is cumulated to certain state, the steel tube of CFT pile is fractured by tension.A fatigue life equation was obtained for CFT pile based on the Manson-Coffin relationship. The curves about deformation and fatigue life are gained with the new model. Comparative previous test data showed that the proposed equation provides a reasonable estimation to the fatigue lives of testing results from literature with acceptable conservatism in most of the cases. Integrated linear Miner cumulative damage theory and steel concrete piles cycle energy law, an energy based cumulative damage model are obtained for CFT piles. Based on the concepts of continuum damage mechanics and standard inelastic analysis of CFT pile, a lumped damage model is provided for modeling the hysteretic behavior of CFT pile. The model is welldefined in physics and mechanic, and also it is very simple in nature which makes it convenient for damage analysis of CFT piles.