Numerical Analysis And Optimization Studies Of Mechanical Behavior Of Diaphragm Wall-waler Beam-strut Reinforced Concrete Joint

In order to improve construction efficiency and practice the concept of green construction,in a prefabricated subway station project in Guangzhou,the underground diaphragm wall-waler beam-sturt joint of the temporary supporting system will be used as a permanent wall-beam joint.Therefore,the reliability of the joint connection affects the overall safety of the station structure.The connection methods of the joints consist of mechanical couplers connection and embedded steel plate connection.However,there are still few studies about the mechanical behavior of this kind of joint and the mechanical performances of the joints with different connection methods are quite different.The mechanical behavior of the wall-beam-strut joint in this project still needs further study.In this paper,based on this project,combined with the existing full-scale experiments of the joints,the mechanical performances of mechanical couplers connecting joints and steel plate connecting joint were studied through numerical simulation.Firstly,the effectiveness of the numerical models was verified by experimental data.Further discussions on the factors affecting the mechanical behaviors of the joints have been conducted,and some relevant optimization suggestions were given.Finally,based on the numerical results,the theoretical hysteretic models of the joints are established,which provides a reference for the overall elastoplastic analysis of the new prefabricated metro stations.The main research contents and conclusions of this paper are as follows:1.Based on an in-depth analysis of existing experimental data,the crack development characteristic can be divided into three phases and the failure mode of the joints was the bending–shear failure.Based on the failure mode,the theoretical bearing capacities of the joints were calculated by a layered fiber beam method and the results showed a good agreement with the ultimate bearing capacities recorded in monotonic loading tests.2.Three-dimensional models of the joints were established through a finite element software called ABAQUS,and the parameter sensitivity was carried out for the numerical results.The effectiveness and accuracy of the numerical models were verified by comparing them with the load-displacement curve,crack distribution,and reinforcement stress distribution obtained from the test results.Based on the verified numerical model,the influences of the aixial compression ratio of the strut,reinforcement ratio,and other parameters on the static mechanical performance of the joints were investigated.It is considered that the axial compression ratio of the joints connected by steel couplers should be controlled below 0.30,while that of the joints connected by welded steel plate should be controlled below 0.21.3.Through another finite element software called Open Sess,the finite element models of the joints were established to investigate the seismic mechanical behaviors of the joints.After verifying the effectiveness and accuracy of the numerical model in Open Sees by the experimental results,further discussions about the influences of concrete compressive strength,the axial compression ratio of the strut,and other parameters on the seismic performance of the joints were also carried out.The numerical results showed that the energy dissipation capacity of the mechanical couplers connecting joint mainly depended on the longitudinal reinforcement ratio of the strut,while that of the steel plate connecting joint was related to the longitudinal reinforcement ratio of the strut,axial compression ratio,and concrete strength.4.Based on the numerical results calculated by Open Sess,a three-line skeleton model and a six-line hysteretic rule were used to describe the hysteretic models of the joints.The stiffness degradation rules of the joints could be obtained by regression analysis of the numerical results.The hysteretic models proposed in this paper could well predict the test results and reflect the hysteretic characteristic of the joints under cyclic load,providing theoretical references for the overall elastoplastic analysis of the new prefabricated metro station.