PSEUDO-STATIC TESTS OF STIRRUP-CONFINED SQUARE CFST TWO-STORY TWO-SPAN COMPOSITE FRAME STRUCTURE

An experimental study on two two-story-two-span CFST frames with or without internal stirrups subjected to horizontal cyclic loading was conducted. The frame specimens were scaled down to 2∶5. The objective of this study is to investigate the influence of stirrups welded inside the CFST columns on the aseismic performance of the frames. Numerical analysis was carried out using ABAQUS, and the finite element model was verified by comparing the test results. Based on the FE models, the influence of the equivalent stirrup ratio was investigated. The experimental and numerical analysis results indicate that the stirrups reduce the slippage between steel tube and infilled concrete and, strengthen the confinement effect of steel tube on infilled concrete at same time. Moreover, the flexural bearing capacity and energy dissipation capacity of the frames were improved. The stirrups also change the ratio of line stiffness and flexural bearing capacity between beam and column indirectly. Compared with the conventional frames, the frames designed using ‘strong columns’ can improve the stiffness, bearing capacity and energy dissipation capacity of the frames by more than 70%, 20% and 50%, respectively.