Aseismic Performance Test And Ductility Analysis Of PHC Pipe Piles

PHC(Prestrestressed high strength concret)pipe piles are widely used in project due to many advantages such as the faster speed of construction the higher bearing capacity of a single pile.A lot of earthquake disaster investigaions indicate that PHC pile often damage under seismic loading because of the poor flexural capacity.The failure mode and seismic performance of PHC and PRC(Pre-stressed High Strength Concrete Reinforced with Nonprestressed Steel Bars)pipe piles are studied in this paper by low-cycle loading tests.A series of measures are proposed on the basis of this study to improve the mechanical performance of traditional pipe piles and the cyclic loading tests are conducted to investigate the improved effects on the seismic performance of PHC pipe piles provided by these measures.The failure mode of PHC pile is brittle from the test results.The failure mode of PHC pile is ductile from the test results.It indicates that filling non-prestressed bars is positive for improving the failure mode of pipe piles.The seismic test of PRC pipe piles with hybrid reinforcements indicates that the bearing capacity,the dissipation capacity and the ductility of PRC pipe piles are better than PHC pipe piles because of filling non-prestressted steel bars.Besides,the peak load of PRC pipe piles increased by 30%~60% comparing with PHC pipe piles.The peak load of PRC pipe piles increased and the ductility of PRC pipe piles decreased as the increase of reinforcement strength ratio.The finite element analysis is carried out to evaluate the performance of pipe piles under low cyclic loading,and the results are verified with the test results.The parameter analysis is done to study the seismic performance of the PRC pipe piles.It shows that the peak bearing capacity of PRC pipe piles increases with increasing nonprestressed reinforcement ratio and prestressed reinforcement ratio.The displacement ductility coefficient of PRC pipe piles decrease with increasing reinforcement strength ratio.For PHC pipe piles,The improvement of twin bars is better than that of equi-spaced bars.The relationship between the displacement ductility coefficient and the curvature coefficient is worked out in regression analysis.The limit of the displacement ductility coefficient of pile piles in seismic zone is [??] = 3.2,and the limit of the displacement ductility coefficient of PRC pile is [??] = 3.3.The limit of the displacement ductility coefficient of PHC pipe piles and the limits the displacement ductility coefficient of PRC pipe piles needs unity to [??] = 3.3.It can ensure the ductility requirement of pipe piles in the seismic regions.