STUDY ON SKELETON CURVES AND HYSTERETIC FEATURES OF COUPLING BEAMS

As a major energy dissipation component of shear-walls, the reinforced concrete coupling beam in the shear-walls possess a great influence on the aseismic performance of structures under a rare earthquake. The mechanical characteristics and ultimate deformation capacity of the coupling beams under revered cyclic loading were focused, the experimental results of 47 coupling beams at home and abroad were analyzed comprehensively. The damage behavior of the coupling beams is closely related to the reinforcement scheme. Affected by cross cracks of concrete and sliding of steel bars, the hysteretic curves of a coupling beam with parallel reinforcement are severely pinched. For the coupling beam with a small aspect ratio, the energy dissipation capacity can be improved by using diagonal reinforcements or synthetically diagonal reinforcements. The bending moment and deformation angle are introduced to present the relationship between the internal force and deformation of coupling beams, the influence of bending deformation, shear deformation, concrete cracking and steel bar slip can be considered synthetically. The results of parameter analysis for span-depth ratio, stirrup eigenvalues and shear force-shear resistance ratio of coupling beams show that the reinforcement scheme has little effect on the ultimate deformation angles of coupling beams. Based on the test results under reversed cyclic loading, the standard M-θ skeleton curve for coupling beams is obtained, which is consistent with requirements relevant to coupling beams in China design specifications, and can be applied in elasto-plastic analysis easily. The control parameters of the hysteretic curve are determined by assuming that the unloading stiffness is the same as the loading stiffness, that both area is enveloped by the test hysteresis loop, and that the simplified hysteresis loop are equal. The simplified hysteretic curve of a coupling beam is in a good agreement with the experimental results.