| Recent year, the steel strength grade applied to reinforced concrete structure in China was mainly within the range of 300 ~ 400 MPa, which was lower than the European and American developed countries. With rapid development of economic in our country, long-span structures and high-rise buildings are increasingly required and needed. The reinforcement with low strength was applied to the practical engineering, which frequently caused construction difficulties, especially in the exterior beam-column joint where the reinforcements are arranged intensively. A large number of earthquake damage shows that the failure of beam-column joint generally leads to the structure overall collapse. Hence, using high performance reinforcement and its application in practical engineering structure are imperative.This paper focuses on the seismic behavior of exterior beam-column joint with HRB 500 E reinforced concrete. Three full-scale exterior beam-column joints with HRB 500 E reinforced concrete were tested under quasi static load. The development of crack that is observed by a hand microscope is described in detail. The characteristic values of seismic behavior of exterior beam-column joints, such as beam end load-displacement curve, envelope curve, ductility factor, energy dissipation and stiffness degradation were obtained through the experiment. The influence of axial load ratio and the core stirrup ratio on seismic behavior of exterior beam-column joint were studied.The test phenomenon observations showed that all of the specimens had the same failure mode which was the flexural failure of beam with little cracks in joint core. Both the axial load ratio and core stirrup ratio had a certain influence on the development of crack. All of the specimens had good seismic behavior. Compared with the horizontal shear values of exterior beam-column joint generated from experiment, the shear design values obtained by formula provided in GB 50010 were partial conservation. The suggestion of improving the shear design values of exterior beam-column joint was thus proposed. As all of the specimens occurred flexural failure of beam, the beam flexural deformation was observed to contributed mostly towards the specimen overall deformation. Higher axial load ratio and core stirrup ratio were found to decrease the joint contribution.The finite element models of exterior beam-column joints with HRB 500 E reinforced concrete were established by OpenSees. The parameters for shear panel component of BeamColumnJoint element in model can be obtained by the Modified Compression Field Theory. The numerical results agreed well with test results. In the parametric study, the influences of beam reinforcement ratio, steel strength grade, concrete strength grade, core stirrup ratio and axial load ratio on the seismic behavior of exterior beam-column joint with HRB 500 E reinforced concrete were further studied. The results indicated that each unique variable had a certain influence on the exterior beam-column joint. More exactly, it can spread damage location from the beam to the joint core, and had great influence on ductility and energy dissipation. |
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