Study On The Seismic Performance Of Reinforced Concrete Beam-Column Space Joints

Reinforced concrete(RC)frame space joints are more complex in terms of forces,bearing beams in both main axis directions,as well as loads from the upper and lower columns,and their reliability is crucial to the safety of the entire frame structure.However,a large number of earthquakes have shown that more RC frame joints have been damaged under the action of ground shaking.However,the actual ground shaking is random and arbitrary in nature,and its direction of action may be at an arbitrary angle to the space joint,i.e.the space joint may be subjected to forces in both principal axes at the same time(bi-directional force),resulting in changes in the joint force performance compared with that in the case of uni-directional force in the principal axes.In this paper,to study the seismic performance of RC space joints under bi-directional forces,low circumferential reciprocal cyclic loading tests were designed and carried out on three RC space joints under bi-directional forces,and the damage mechanism,hysteresis curve,skeleton curve,energy dissipation capacity,ductility and stiffness of the space joints were investigated.Based on the force characteristics of the spatial joints,a numerical model of the shear bearing capacity of RC spatial joints was established and a formula for calculating the shear bearing capacity was proposed.Based on the test results,the finite element software ABAQUS is applied to carry out parametric extension analysis of the space joints,and the results obtained are as follows:(1)With the increase of loading angle(0°～45°),the shear bearing capacity of the space joint increases,the energy dissipation capacity and ductility become worse,and the stiffness degradation increases;with the increase of volume matching hoop ratio(1.88%～3.35%),the shear bearing capacity of the space joint increases,and the energy dissipation capacity and ductility become better.(2)Based on the force characteristics and transmission mechanism of space joints,the formula for calculating the effective compression area and inclination angle of RC space joints under bi-directional force is derived,and the formula for calculating the shear bearing capacity of space joints can be directly calculated.The calculation formula can reflect the shear bearing capacity of the space joint under two-way force better than the test value of shear bearing capacity of RC space joint.(3)The influence of reinforcement ratio and loading angle on the seismic performance of spatial joints was analyzed using finite element software ABAQUS.The results showed that as the volume reinforcement ratio of spatial joints increased,the increase in the bearing capacity of the specimen slowed down;As the loading angle increases,the bearing capacity of the specimen decreases and the energy consumption capacity deteriorates.