Study On Seismic Behavior And Bearing Capacity Of New Type PHC Pile

Prestressed high-strength concrete pipe pile(PHC pile)has been widely used in more and more engineering projects due to its high bearing capacity,good pile quality and wide application range.The range of application in earthquake zone with 8 degree seismic fortification intensity is restricted because of the drawback of horizontal bearing capacity of traditional PHC pile under earthquake.The seismic behavior and bearing capacity of new type PHC pile provided by Jianhua Construction Materials(including PHC pile with cgl and cg2 ultra-high strength concrete,PHC pile with high-ductility steel bar and PHC pile with concrete admixture or carbon fiber)are analyzed in this paper.The research results can provide reference for design and application of PHC pile under earthquake.The main research work and results are as follows:(?)Twelve new type PHC-400-AB piles were tested under low cycle reserved loading to study the seismic behavior such as failure mechanism,hysteresis curve,skeleton curve,strength and stiffness degradation,ductility performance and energy dissipation.Three parameters,grade of concrete,steel bar material and concrete autoclave process are taken into consideration.The experimental results indicate that PHC pile reinforced with high-ductility steel bar shows good ductility performance and energy dissipation,and the addition of carbon fiber in concrete can improve crack resistance and ultimate bearing capacity.(?)According to the shear strength,crack resistance and ultimate bending moment of PHC pile,the derivation process and theoretical significance of various calculation methods were analyzed.By comparing the theoretical calculation with the experimental results,the modified formula of crack resistance and ultimate bending moment is put forward by adding correction coefficient of ultra-high strength concrete(cgl and cg2)and material coefficient considering concrete admixture.An effective way to improve crack resistance and ultimate bending moment is put forward based on the sensitive analysis of the modified formula.(?)A finite element model was set up by ABAQUS to study the nonlinear simulation of PHC pile under monotonic loading.The law of change of stress and strain is consistent with the experimental results,which shows the finite element analysis model is reasonable and reliable.The load-displacement curve of new type PHC pile was obtained by adjusting model parameters.The simulation results show the bearing capacity is similar to that of the experiment.Furthermore,the bending capacity of PHC pile can be improved by increasing the reinforcement ratio of prestressed steel rather than stirrup.