Seismic behavior of concrete-filled circular steel tubular columns considering initial stress

Due to the special construction mode of concrete filled steel tube (CFST) and the long-term shrinkage creep of concrete filled steel tube, the actual working stress state of the structure is obviously different from that of single loading under conventional laboratory conditions. To a certain extent, it can be simplified as the initial stress problem of steel tube. In order to explore the effect of initial stress of steel tube on the seismic performance of CFST columns, 6 unidirectional pushing and repeated low cycle loading tests of CFST columns were completed, and the influence of initial stress of steel tube on failure mode, skeleton curve and hysteretic curve of specimens were emphatically analyzed. On this basis, solid model and fiber model was adopted respectively to simulate the test and carry out paremetic analysis by considering the effect of initial stress of steel tube. The seismic behavior of CFST column models were simulated and analyzed. The results show that the initial stress of steel tube has an obvious effect on the lateral thrust performance of CFST columns. The larger the initial stress, the lower the lateral thrust bearing capacity of CFST colums. The initial stress of steel tube has no obvious effect on its seismic performance, only reduces the stiffness of the hysteretic curve at the initial stage of loading. With the increasing number of cycles, the effect of the initial stress of steel tube is limited. This study provides a reference for seismic performance evaluation of CFST columns considering the influence of construction and service process. © 2019, Editorial Office of Journal of Building Structures. All right reserved.