Experimental Study And Finite Element Simulation On Seismic Performance Of The Compound Reinforced Prestressed Hollow Square Pile

Because of the high brittleness character of the prestressed high-strength concrete hollow square pile(hereinafter referred to as prestressed hollow square pile)under earthquake,compound reinforced prestressed hollow square piles are made by collocating non-prestressed steel bar to improve the seismic performance.In this paper,the horizontal load-bearing capacity and seismic performance of the prestressed hollow square piles and the compound reinforced prestressed hollow square piles are researched by full-scale test on site and finite element simulation.(1)The trend of the hysteresis curves,skeleton curves,ductility and rigidity of the prestressed hollow square piles and the compound reinforced prestressed hollow square piles are studied by applying a low-cycle reciprocating load to them.The research results show that the prestressed hollow square pile occurred brittle failure and the compound reinforced prestressed hollow square piles occurred ductile failure.The latter have plumper hysteresis curve and their seismic capacity is better with the increase of reinforcement ratio of non-prestressed steel bar.The ductility coefficients of the compound reinforced prestressed hollow square piles are greater than 3 and exist a optimal value.They increase and then decrease with the increase of reinforcement ratio of non-prestressed steel bar.Pile displacement and bending moment have focused on upper part of the piles.With the increase of reinforcement ratio of non-prestressed steel bar,the maximum bending moment positions appear downward trend.(2)The unidirectional loading tests of the prestressed hollow square pile and the compound reinforced prestressed hollow square piles were carried out at the original test site to investigate whether the seismic performance of the piles can be judged by replacing the reciprocating loading test with the unidirectional loading tests.The research results show that it is feasible to evaluate the horizontal load-bearing property and stiffness of the compound reinforced prestressed hollow square piles.It is better to use the load-displacement loading system when evaluate the seismic performance of the compound reinforced prestressed hollow square piles by unidirectional loading system.(3)The ABAQUS finite element software was used to simulate the seismic behavior of the compound reinforced prestressed hollow square piles.The simulation results are close to the test results.The parameters affecting the horizontal bearing capacity and the seismic performance of the compound reinforced prestressed hollow square piles were analyzed.The research results show that the ductility of the compound reinforced prestressed hollow square piles can be improved by increasing the reinforcement ratio of non-prestressed steel bar and the maximum ductility is obtained when the ratio of non-prestressed steel bar is 0.74%.The horizontal bearing capacity and ductility can be improved by increasing the moment of inertia of section.The ductility is not significantly affected by changing the reinforcement ratio of prestressed steel bar,the pile thickness and the pile length.