Study On Seismic Behavior Of Concrete Filled Steel Tube Double Piles To Cap Foundations

The concrete filled steel tube pile has been widely used in wharf structure,bridges and super high rise buildings in recent years because of its advantages of high stiffness,great bearing capacity and excellent seismic performance.However,the current code lacks relevant provisions for aseismic design of concrete filled steel tube double piles to cap foundations,at present,little research on the seismic performance of concrete filled steel tube double piles to cap foundations.Therefore,in order to popularize the application of concrete filled steel tube pile to cap foundation in earthquake area,the seismic performance of the concrete filled steel tube double high piles to cap foundations has been tested and studied in this paper,the main work and achievements are as follows:(1)Three concrete filled steel tube double piles to cap foundations and two concrete filled steel tube single pile to cap foundations are tested under low frequency cyclicing load,compared the study on the seismic damage mechanism of equal height,double straight piles,equal height double inclined piles,unequal high double inclined piles and single straight pile caps under different axial compression ratios,obtained the seismic performance of hysteretic curve,skeleton curve,bearing capacity,axial force distribution,stiffness,ductility and energy dissipation capacity.(2)Experimental research shows that the equal high double straight piles to cap foundations have the best ductility,but its bearing capacity,initial stiffness and energy dissipation capacity are the lowest,while the unequal high double inclined pile foundation has the worst ductility,but its bearing capacity,initial stiffness and energy dissipation capacity are the best,the aseismic performance of the equal high double skew pile is between the two.The test results show that increasing axial compression ratio can improve bearing capacity and initial stiffness of specimens,but have negative effects on ductility and stability in elastoplastic state of specimens.(3)The numerical simulation method of double pile cap foundation based on finite element software ABAQUS is studied,and The calculated Pushover curve agrees well with the experimental curve,based on the test model,the steel yield strength,concrete strength,axial compression ratio,steel tube wall thickness,angle and ratio of unequal height are further studied,the analysis results have certain reference value to the future of the research of concrete filled steel tube double piles to cap foundations.