Study On Seismic Behavior Of New Self-resetting Steel Truss Connection Beam

As the first aseismatic defense line of coupled shear wall structure,the link beam is damaged and dissipates energy first under the action of earthquake.However,the traditional link beam has the problems of large residual displacement,difficult repair and high repair cost after earthquake.In recent years,some scholars have put forward the concept of self-resetting connection beam.The connection beam and wall limb are prefabricated respectively,connected by prestressed tendons,and energy dissipation devices are installed at the connection part of the connection beam and wall limb.In the process of wall limb deformation,the connecting beam rotates around the corner,so that the prestressed tendons elongate and the residual displacement is reduced.However,in the process of rotation,the axial displacement of the connecting beam increases,which contradicts the assumption of rigid floor slab.Aiming at the above problems,a new type of self-resetting steel truss connection beam is proposed in this paper,which is studied from the aspects of theoretical analysis,test verification and numerical simulation analysis.Firstly,the quasi-static tests of self-resetting damper and self-resetting steel truss connection beam are carried out,and the bearing capacity calculation formula of self-resetting steel truss connection beam is proposed.Secondly,ANSYS software was used for numerical simulation to verify the accuracy of the numerical model.Finally,the seismic performance of the connecting beam was analyzed parameterized.The main research contents include:(1)For the design of the new self-resetting steel truss connection beam,it is connected with the wall limb in the form of articulation,which avoids the axial elongation effect in the self-resetting steel connection beam.The mechanical model and the calculation formula of bearing capacity of the self-reset friction damper were deduced.Based on the mechanical model and the calculation formula of bearing capacity,the calculation formula of shear bearing capacity and residual displacement of the self-reset steel truss were deduced.(2)The Shape Memory Alloy(SMA)rod,self-resetting friction damper and self-resetting steel truss connection beam were tested.In this paper,axial cyclic tensile test of SMA rod,self-resetting friction damper and pseudo-static test of self-resetting steel truss connection beam were systematically conducted.The results show that: The SMA rod used in this paper was heat-treated at 450 ℃ for 30 minutes,and the residual strain was less than 0.5% when the cumulative strain was 5%.The self-resetting friction damper has good self-resetting ability and energy dissipation capacity under cyclic load,and the hysteresis curve of the damper is full and shows a "flag" type.In the pseudo-static test,the self-resetting steel truss connected beams show good energy dissipation capacity,and the residual displacement is greatly reduced compared with ordinary concrete connected beams and steel connected beams.(3)The ANSYS software is used to establish the self-resetting steel truss connected beam model and verify the correctness of the finite element model.Firstly,the axial tensile test of SMA rod was simulated,and the results were in agreement with the experimental results to verify its correctness.Secondly,a self-resetting friction damper model is established,and the error between the output force simulation results and the test results is within 3%.Finally,the self-resetting steel truss connected beam model is established and the parametric analysis is carried out.The results show that the difference between the simulation results and the mechanical model is only 7.2%,which verifies the correctness of the model.The bearing capacity and stiffness of the connecting beam increase with the increase of the torque of the belly bar,the energy dissipation capacity is enhanced,but the residual displacement is increased.With the increase of the diameter of SMA rod,the initial stiffness,bearing capacity and energy dissipation increase,while the residual displacement decreases.With the increase of the pretension of SMA rod,the initial stiffness and bearing capacity of the connected beam increase,and the residual displacement decreases,which has little influence on the energy dissipation.