Research On Deformation Limits Of New Prefabricated Shear Wall Based On Material Strain

Performance based on seismic design is a design method to realize hierarchical control under earthquake damage by evaluating the performance state of components on the basis of meeting the seismic fortification objectives of structures.The key is to obtain the performance index limits that quantify the performance state of components.China’s current seismic codes mainly use the checking calculation of bearing capacity and elastoplastic deformation to judge the performance level of components,but have not given the deformation index limit to quantify the different performance states of components.At the present stage,the development of prefabricated structures is an important way to achieve the goal of “double carbon” in the building industry.Existing research at home and abroad focused mostly on the connection behavior and seismic performance of structures,while there are few studies on the performance state evaluation based on deformation.Therefore,performance based seismic design is introduced in this paper to study the deformation index limits of the proposed new type of prefabricated shear wall connected with “bolt and U-shaped channel steel”.It mainly includes the following aspects:(1)Based on the completed seismic performance test of the new prefabricated shear wall,the friction-slip mechanism between bolts and U-shaped channel steel is analyzed.Through the simplified analysis of the component stress state,two adverse states of high-strength bolts are identified,and the formulas for calculating the shear capacity under the corresponding state are proposed,which provide the design basis for the establishment of the subsequent batch finite element models.(2)The finite element simulation is carried out by ABAQUS,and the parameter settings in the steps including material constitutive,element type and mesh division,interaction,loading mode and boundary conditions are defined.The rationality of the modeling scheme is verified by comparing with the tested load-displacement curves and failure modes.(3)Based on factorial design,a total of 216 finite element models are established by changing shear span ratio,axial compression ratio,longitudinal reinforcement ratio of edge members,stirrup characteristic value,horizontal distribution reinforcement ratio and flexural shear ratio.The failure modes of components are divided into three categories: flexural failure,flexural-shear failure and shear failure.Then the failure modes of all models based on finite element recognition are determined.According to the factors analysis results of component failure modes,the shear span ratio and the flexural shear ratio are taken as the discriminant indexes,and the classification criterion of failure modes of the new prefabricated shear wall with good prediction accuracy and representative rate is proposed.(4)Referring to China’s seismic codes and relevant literature,the flexural failure and flexural-shear failure components are classified into six performance states: intact,slightly damaged,slightly-moderately damaged,medium broken,severe broken and invalid.The shear failure components are classified into two performance states: intact and severe broken.The criterion of component performance state based on strain limit of concrete,strain limit of reinforcement and bearing capacity is determined.(5)The displacement angle is selected as the quantitative performance index,and the formulas for calculating the displacement angle limit values of each performance state under different failure modes are obtained by liner regression analysis.Subsequently,through the correlation analysis,it is clear that axial compression ratio and flexural shear ratio are the key factors affecting the limit value of the deformation index of component under flexural failure and flexural-shear failure.The shear span ratio and the longitudinal reinforcement ratio of edge member are the main factors affecting the limit value of the deformation index under shear failure.According to the statistical analysis results,the deformation performance limit standards of new prefabricated shear wall with a 90% guarantee are given,which provides a basis for improving the performance-based seismic design.