Numerical Analysis Of Seismic Performance Of Rc Frame Beam-column Joints Under Multi-dimensional Ground Motion

The damage caused by the major earthquakes in China in recent years shows that apart from the fact that reinforced concrete(RC)frame structures are prone to damage due to plastic hinges at the beam and column ends,the failure of beam and column joints also leads to their overall damage It is one of the main forms of this,which does not realize the design principle of "strong nodes and weak members" in the seismic code.Investigate the reason,China's "Code for Seismic Design of Buildings"(GB50011-2010)Article 5.1.1 stipulates: In general,the horizontal earthquake action should be calculated at least in the direction of the two main axes of the building structure.In this direction,the anti-side force member bears.However,the ground motion is random and multi-dimensional,and its input in the horizontal direction may be along any angle of the structure,which results in the simultaneous loading of the frame nodes in both directions,and its force mechanism and destruction mechanism change,which is different from that of the main axis.The situation is different.Therefore,it is necessary to clarify the seismic performance of reinforced concrete frame space nodes under multi-dimensional ground motion.In this paper,the finite element analysis software ABAQUS is used to carry out the bearing capacity,stiffness,and deformation capacity of the node under the monotonous load of the reinforced concrete frame space node under different horizontal loading angles.Numerical simulation analysis of seismic performance such as hysteresis curve characteristics,energy dissipation capacity,ductility,etc.In addition,parameter expansion analysis was carried out for the influence of axial compression ratio and coupling rate on the mechanical performance of space nodes;The numerical analysis method of the space node of reinforced concrete frame,the main achievements are as follows:(1)Under the monotonic load,when the horizontal loading angle is 0 °,15 °,22.5 °,30 °,45 °,the shear capacity of the reinforced concrete frame space node decreases as the loading angle increases;(2)Under the effect of low-cycle reciprocating load,the greater the horizontal loading angle,the more severe the damage of the frame joints.The worse the anti-seismic performance of stiffness,bearing capacity,ductility,energy consumption,etc;(3)Under the action of monotonic load and reciprocating load,when the horizontal loading angle is 45 ° and 30 °,the shear failure of the reinforced concrete frame node occurs,and the design concept of “strong node weak member” fails;under 22.5 ° loading,The failure occurred at the end of the beam,and the damage degree of the joint was significantly lower than that at the end of the beam;when the horizontal loading angle was 15 °,the beam hinge failure mechanism occurred at the joint of the reinforced concrete frame;(4)Under the effect of unidirectional loading and reciprocating loading,the effect of different axial compression ratios and coupling ratios on the performance of the joints is studied.The stronger the seismic performance of the frame joints,the smaller the conversely.Increasing the node stirrup rate can improve the seismic performance of the node;under the premise of the same stirrup rate,changing the stirrup diameter and changing the stirrup spacing has no effect on the seismic performance of the node;(5)Establish a numerical analysis model of reinforced concrete spatial node softening tension-compression rod,and use this method to calculate the shear capacity of the model simulated in this paper.The shear bearing capacity of the node under different loading angles calculated by the analysis model is close to the numerical simulation analysis result.This method can be used to estimate the bearing capacity of the space node.