| As a major form of steel-concrete composite structures, steel reinforced concrete (SRC)structures which possess high bearing capacity, excellent integral stiffness and seismic behavoirs have been widely used in high-rise buildings, super high-rise buildings, long-span and heavy-load structures. The plastic hinge of SRC frame structure occurs firstly at the end of frame beams to dissipate seismic energy under earthquake, therefore, the mechanical properties of SRC frame beams have become a major factor to influence seismic performance of SRC frame structures. This paper was devoted to studying on seismic damage of steel reinforced high strength and high performance concrete (SRHSHPC) frame beams by the way of combining physical model experiment and theoretical analysis.Firstly, based on the experimental results of 5 SRHSHPC frame beam specimens which are tested under low cyclic reversed loading, the crack development and failure model of frame beam specimens were discussed, and the loading-displacement hysteretic curves and skeleton curves of frame beams were obtained; the law and characteristics of the strength and stiffness degradation, ductility and energy dissipation capacity of frame beams with different steel rations and stirrups ratios were analyzed. The results indicate that the SRHSHPC frame beams subjected to low cycle reversed loading produce flexure failure normally by reasonable design, and possess good ductility and energy dissipation capacity. As the increase of cycle number and horizontal displacement amplitude, the damage of specimens is accumulated gradually, which causes strength and stiffness degradation and the decrease of energy dissipation capacity. However, the strength and stiffness degradation amplitude are decreased, and the energy dissipation capacity is improved by increasing stirrups ratios and steel rations. The research will supply experimental support for establishing seismic damage model and revealing the effect of damage on mechanical property of SRHSHPC frame beams further.Based on the test results, the seismic damage characteristic of SRHSHPC frame beams was analyzed. The deficiency of existing seismic damage models was concluded. A new seismic damage model of SRHSHPC frame beams was proposed, which is a non-linear combination of the deformation and accumulative damage of beam. The damage indexes of tentative frame beams were calculated, and the influence of steel rations and stirrups ratios on damage performance was discussed. The study results will supply the theory support for the seismic damage assessment and the establishment of damage-based earthquake-resistant design method of SRHSHPC members. |
