| Steel reinforced concrete structure is the combination of ordinary reinforced concrete structure and steel structure, which possessed the advantages of these two ordinary structure. Its mechanical performance is better than the simple superposition of concrete and steel because of associated effects, which determines its prominent advantages and broad application prospects in structural seismic.Based on the four-group low cycle repeated loading test of SRC composite torsion member completed, the paper analyzes the hysteretic behaviors of 25 specimens. The results shows obvious pinch phenomenon of hysteretic curve in each specimen and obvious degradation phenomena of unloading stiffness after elastic period but before cracking. With the same magnitude of repeated load, the bearing capacity of the third load is significantly less than that of the first load, and the strength will be degraded. With obvious "tri-linear" feature, skeleton curves of all specimens can be divided into three periods: elastic period before cracking, elastic-plastic period from cracking to achieving maximum carrying capacity and strength degradation period. According to the above features, the skeleton curve is defined by the parameters of cracking torque, stiffness before cracking, peak torque, secant stiffness of the peak torque and stiffness in strength degradation period. Then unloading stiffness and strength degradation under repeated loading are analyzed. Finally, according to the test hysteresis curve, the restoring-force model for steel encased concrete members subjected to combined torsion was established by the hysteretic rules seizing the main features and abandoning minor hysteresis characteristics.Finally, the finite element analysis on this subject is conducted by ABAQUS, which shows that the results of test and simulation are very close to each other, proving the validity of the finite element analysis in the research of SRC structure. |
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