Study On Seismic Behavior Of Reinforced Concrete Beam-multiple Composite Core Column Joins

Reinforced concrete structure has been widely used in engineering construction.The reinforced concrete frame joints in the form of general reinforcement have been comprehensively and systematically tested and theoretically analyzed by many scholars at home and abroad.From theoretical analysis to design calculation,it has become more and more mature.Compared with the common reinforced concrete columns,the multicomposite core columns have better aseismic performance.However,there are few researches on the aseismic performance of the joints composed of multi-composite core columns at home and abroad.Based on the experiment of reinforced concrete joints with multiple core reinforced by Yang Chengyu from Chang ’an University,this paper adopts the method of combining theoretical research and finite element analysis to study the seismic performance and influencing factors of reinforced concrete beam-multiple composite core column joints under low cyclic cyclic load.Based on the model of softened tension-compression bar,the shear capacity calculation formula of reinforced concrete beam-multiple composite core column joints is established.The main work and achievements of this paper are as follows:(1)The horizontal shear capacity of the three joints was calculated by using the softened tension-compression bar model and compared with the actual shear capacity of the specimens.It was found that there was a good agreement between the two,indicating that the softened tension-compression bar model could be used to calculate the shear capacity of such joints.(2)Based on the good ABAQUS model and experimental simulation,the influence of axial compression ratio on the seismic performance of joints is analyzed: the larger the axial compression ratio is,the lower the horizontal bearing capacity and ductility of such joints are,but the better the energy dissipation capacity of joints is,and the influence of axial compression ratio on stiffness degradation of joints is not obvious.(3)Based on ABAQUS model and good simulation experiment,the analysis of the effect of shear span ratio on seismic performance of node: the shear span ratio,the greater the level of the lower bearing capacity,ductility,the worse but still can reach 3.0,indicates that the node within the shear span ratio of 2.0 to 5.0 has the very good energy dissipation capacity,shear span ratio increases,the less stiffness degradation.(4)Based on the good ABAQUS model and test simulation,the influence of concrete strength on the seismic performance of joints is analyzed:With the increase of concrete strength grade,the ductility of joints decreases(at 65 MPa,there is still a good ductility).The more energy dissipated in the hysteretic loop,the more energy dissipated in the hysteretic loop,and the greater the initial stiffness of joints.However,the decreasing trend of stiffness is less affected by the strength grade of concrete.