Seismic Performance And Ductility Analysis On Pile To Pile Cap Connections

The prestressed high strength concrete pile(PHC pile)is widely used in the engineering construction with the rapid development of civil engineering in China,such as buildings,bridges,ports and docks,and so on.The pile end in the pile to pile cap connection is easy to occur to bending shear failure cuased by pressure,tensile,compression and shearing under seismic action.Therefore,it is significantly important to further research the seismic performance of the pile end and expanding the application scope of the pile in the engineering.The seismic performance and ductility of the pile end in the PHC pile to pile cap connection and the prestressed high strength concrete pile with non-prestressed bars(PRC pile)to pile cap connection are respectively researched by the low cyclic loading test and finite element analysis in this paper,and provide reference for evaluating the seismic performance of the pile and the application of pile in the engineering,and provide the basis for the pile standard revision.The foureteen pile to pile cap connections are tested under low cyclic loading to study the seismic behavior of pile to pile cap connections.The test parameters include axial compression ratio,the connection form,the depth of pile embedded into the pile cap,the amount of anchor reinforcement and pile type.It is indicated that the failure modes of pile end are more tended to brittle shear failure characteristic with the increase of axial compression ratio from the results,and specimens have a higher lateral bearing capacity,and the energy dissipation capacity,deformation performance and ductility are reduced.The normal connections with the axial compression ratio not more than 0.3 have a higher lateral bearing capacity compared with cut-off pile connections,and the deformation and ductility performance are superior.The rotation capacity of connections is reduced with the increase of the embedment depth and the anchor reinforcement amount,so that the deformation and ductility performance are poorer.The pile end failure mode is improved with the configuration of non-prestressed tendons,and the energy dissipation capacity,bearing capacity and deformation of the specimens are better than those of PHC pile,which is beneficial to expand the application range of the pile in engineering.The relationship between the curvature ductility and displacement ductility of the pile end is fitted,and the displacement ductility limit value is put forward based on the low cyclic loading test.At the same time,the effect of different parameters on the ductility performance of the PHC pile end and the PRC pile end is analyzed.It is indicated that the relationship of curvature ductility factor and displacement ductility coefficient of PHC pile end and PRC pile end are exponential function relationship.The displacement ductility coefficient limit value of the seismic region above 7 degree is conservatively recommended by [??]=3.3.The PHC pile with 0.15 axial compression ratio and 50 mm embedded depth and the PRC pile with axial compression ratio no more than 0.30 can be used at the seismic zone above 7 degree.The finite element analysis on pile to pile cap connection is carried out by Opensees.The calculated results are well agreement with the experimental results.The hysteretic curves of the specimens are plumper with the increase of the diameter of the non-prestressed bars,the energy dissipation capacity is improved,and the lateral bearing capacity and deformation are improved.