Study On Seismic Performance Of Pipe Piles Considering Soil-pile-superstructure Interaction

As a kind of prefabricated pile, prestressed concrete pipe pile has lots oftechnical and economic advantages. It is used widely in soft area along the east coastof China. Due to the short application time and complicated stress state, the workingperformance and mechanical characteristics of the PHC pile are still not clear,especially on the seismic performance of PHC piles. Some specific research need tobe done to guarantee the safety of PHC piles under seismic action.According to the current research situation of pile foundation seismicperformance all around the world, combining the site characteristics of Tianjin, seriesof numerical simulation analysis are carried out. Main contrast factors include thedifferent seismic waves, different soil layer distribution, different framework layernumber, different connection forms between pile head and cushion cap, differentstiffness of pile and the presence of the basement.Based on the current standardization, PKPM software is used to design buildingson two kinds of site in Tianjin. Then, commercial FEM analysis software ANSYS isused to simulate the soil-structure interaction. And the internal force of pile bodyunder three different earthquake acceleration waves is picked up.The study result shows that PHC piles have different performance under differentseismic oscillation, and the internal force distribution of the piles is quite differentfrom the static load test on the pile head. The maximum moment value along the pilebody appears on the pile top and the interface between hard soil and soft soil. Thelayer number of the superstructure has little influence on the pile internal force. Thepile internal force of the nine-layer frame structure even less than the internal force ofthe three-layer and five-layer frame structure. The connection type has directinfluence on the transmission of the inertia force. The research indicates that thearticulated form between pile and cushion tap is preferred considering the seismicperformance. The increase of the pile stiffness will generate lager internal force on thePHC piles under the earthquake; on the other hand, because of the increasement ofbending and shear capacity, the seismic safety of the pipe pile is improved due to thestiffness increase. Different characteristics are shown under different site considering the influence of the basement, and it relates to the soil condition of the scope of thebasement.