Numerical Simulation And Comparative Analysis On Seismic Performance Of Bored Pile And Prestressed Pile

Pile foundation is one of the most common types of foundation,its horizontal bearing capacity and seismic performance have a significant impact on the safety of buildings.The most common pile types are prestressed concrete pipe pile(PHC pipe pile),bored pile and so on.Because the seismic damage of PHC pipe pile foundation is serious,some scholars have studied that adding non-prestressed steel bars to PHC pipe pile can effectively improve its seismic performance.However,the material properties of composite reinforced high strength prestressed concrete pipe pile(PRC pipe piles)formed by adding non-prestressed steel bars have not be looked in detail.The comparative analysis of horizontal bearing capacity and seismic performance of PRC pipe piles with bored piles are not thorough.In this paper,the pile-soil interaction models of PRC pipe pile and bored pile are established based on full-scale field test,the horizontal bearing capacity and seismic performance of each pile type are analyzed by calculations.It provides the corresponding basis for the selection of different pile types in engineering.A three-dimensional finite element model of pile-soil interaction for multi-pile single pile is established based on the analysis of the field quasi-static test results.Reciprocating loads are put on pile top to simulate the loading procedure of field pseudo-static test.The reliability of the model is verified by comparing with the field test results of various pile types.On this basis,the control variable method is used to analyze the influence of different parameters on the seismic performance of pile foundation.The number of non-prestressed steel bars and the constraint stiffness of pile top corner in PRC pipe pile are changed one by one.The reinforcement ratio of bored pile and the constraint stiffness of pile top corner are also changed.The pseudo-static simulation of PRC pipe pile and bored pile with various non-prestressed steel bars reinforcement ratios is carried out,in order to analyze the horizontal bearing capacity and seismic performance of different pile types.The research shows that the displacement ductility of pile foundation tends to decrease after the number of non-prestressed steel bars is halved,compared with PRC pipe piles with 12 non-prestressed steel bars,but the displacement ductility coefficient can still be maintained at more than 3,which meets the seismic requirements of foundation components.With the increase of the rotational restraint stiffness of pile top,the horizontal bearing capacity of pile foundation increases,but the displacement ductility decreases.For bored pile,with the increase of reinforcement ratio,the plastic deformation capacity of pile body increases continuously,the load level increases,and the displacement ductility of the pile increases first and then decreases.According to the displacement ductility coefficient obtained by simulation,the optimum reinforcement ratio of cast-in-place pile is 0.82%.Similarly,the horizontal bearing capacity of bored pile increases and the ductility of displacement decreases with the increase of the rotational restraint stiffness of pile top.When the rotational restraint stiffness of pile top is greater than 4MN m/rad,the top of bored pile will be damaged first,which is not consistent with the actual test.By calculating various non-prestressed steel bars reinforcement ratio model,it shows that the reinforcement strength ratio should be guaranteed in the range of 0.23-0.33,so that the ductility of the composite reinforced pipe pile is at a higher level.When PHC pipe pile is equipped with nonprestressed steel bars,the plastic properties of pile materials can be fully developed as in the material of bored pile,thus improving the displacement ductility.