NONLINEAR ANALYSIS ON MECHANICAL PERFORMANCE OF FRAME STRUCTURES COMPOSED OF STEEL REINFORCED CONCRETE BEAMS AND STEEL-TUBE REINFORCED CONCRETE COLUMNS

Based on the test results of two frame specimens composed of steel-tube reinforced concrete columns and steel reinforced concrete beams under cyclic horizontal loading, the numerical models of the specimens are established by three-dimensional entity elements and fiber beam-column elements, respectively. The mechanical performance and whole process of the hysteresis are studied. The failure mode and the state of stress of steel skeleton, reinforcement skeleton and the prestressing tendons in the specimens are also observed. The parametric analysis of the hysteretic behavior of the frame specimens are conducted. The influence of column slenderness ratio, axial compression ratio, sectional modules and reinforcement ratio, ratio of steel tube in column, steel tube confinement factors, radius-thickness ratio, concrete strength and prestressing level on the composite frame are observed. The hysteretic model of single-storey and single-span composite frame are proposed on the basis of a large number of parametric analysis. The results indicates that the failure modes could be simulated intuitively by the numerical model established by three dimensional entity elements; the hysteretic curves calculated show a plump shape and favorable energy-dissipating capacity in the frame; when the axial compression ratio is bigger than 0.6, the displacement ductility of the frame decreases; the proposed hysteretic model by parametric analysis could give reliable prediction of the composite under horizontal loading.