Research On Mechanical Performance And Bearing Capacity Of New Type Of Outsourcing Reinforced Joint

Adding a layer of steel structure on top of the existing reinforced concrete(RC)frame structure can prolong the service time of the original structure and effectively alleviate the contradiction between the urgent need for urban housing and the shortage of construction land.However,the stiffness and mass of this hybrid structure are prone to sudden changes,and rational design of the connection joint between the old and new structures can reduce the adverse effects of sudden changes,and improve the synergistic performance of the overall structure.The new type of outsourcing reinforced joint proposed by the research group can not only give full play to the linking role of the hybrid joint,but also strengthen the embedded effect of the layered part.In order to promote the promotion and application of this new joint,the paper is based on the previous research of the research group,the multi-parameter expansion analysis of its mechanical performance is carried out,and its bearing capacity calculation method and restoring force model are deeply studied.The main contents and achievements of this research are as follows:(1)With the help of ABAQUS software,a new type of outsourcing reinforced joint model was established,its seismic performance under cyclic reciprocating load is deeply analyzed,and compared with the results of existing experiment[59]to verify the accuracy of the built model.(2)Research on the influence of relevant parameters on the mechanical performance of the new joint.The existing building service time,the axial compression ratio,the beam reinforcement ratio,the concrete strength grade,the wrapped foot’s horizontal length and elevation height are changed,in order to deeply research on the mechanical performance of the new outsourcing reinforced joint by the change of each parameter law of influence.The Results show that:①When the service time of the existing building is less than 32 years,the deterioration degree of its material properties is relatively small,and the impact on the bearing capacity of nodes is relatively small.②When the axial compression ratio is controlled between 0.24 and 0.40,it can not only ensure the reliable connection between the upper and lower structures,but also improve the 0.24 and 0.40,it can not only ensure the reliable connection between the upper and lower structures,but also improve the bearing capacity of the joint.③When the beam reinforcement ratio increases,the joint bearing capacity increases significantly,but when it exceeds 1.40%,the joint will suffer brittle failure.④When the concrete strength grade is controlled between C30 and C45,the ultimate bearing capacity and plastic deformation capacity of the joint are better.⑤Increasing the horizontal length of the enlarging foot can improve the joint’s ultimate bearing capacity,but when it exceeds 0.11 times the length of the concrete beam,it is not conducive to the stress in the core area of the joint.⑥When the height of the expanded footing is between 0.08 and 0.11 times the column height,coordination of the stiffness ratio of the joint’s upper and lower structures,which can give full play to its ultimate bearing capacity.(3)Research on calculation method of nodal bearing capacity.The ultimate bearing capacity data obtained from variable parameter simulation are extracted,and the mathematical relationship between each parameter and the bearing capacity of the joint is established by numerical fitting method,and they are integrated and merged,so the calculation formulas for the flexural and shear bearing capacity of the new outsourcing enhanced joint are proposed.(4)Establish resilience model of joint.The data of skeleton curves and hysteretic curves obtained from variable parameter simulation are extracted,and the trilinear skeleton curve model and stiffness degradation law are established by numerical fitting method.And then,a new type of outsourcing reinforced joint resilience model considering the performance degradation of the existing structure is established.which provides a reference for such joints in elastoplastic seismic response analysis.