Analysis on hysteretic behavior of composite frames with concrete-encased CFST columns

Based on the test results of two composite frame specimens with concrete-encased CFST columns under lateral cyclic loading, the numerical models of the specimens are established by fiber beam-column elements, and the whole hysteretic process are investigated. The parameter analysis of the hysteretic behavior of the frame specimens are conducted, and the influence are observed. The main studied parameters include column slenderness ratio, axial compressive ratio, sectional modules of steel and reinforcement ratio, the ratio of steel tube in column, steel tube confinement coefficient, radius-thickness ratio, concrete strength and prestressing level. The hysteretic models of one-storey and one-bay composite frame are proposed on the basis of a large number of parameter analyses. The results indicated that the hysteretic curves calculated show plump shape, and the frame behaves favorable energy-dissipating capacity and when the axial compression level is bigger than 0.6, the displacement ductile of frames decrease; the proposed hysteretic models by parameter analysis could give reliable prediction of the composite structure under horizontal loading.