Study On Stress Hysteresis Of Concrete Displacement Reinforcement Of Shear Wall

Concrete replacement is a common method used to improve building structural damage caused by insufficient concrete strength,design defects,etc.It is widely used in the reinforcement of concrete walls,columns,and other components.For high-rise buildings,shear walls are important components that ensure the stability of the building under load.When the shear walls that need to be replaced are located near the bottom of the building,resulting in excessive overlying loads,the use of the overall replacement method is complex,expensive,and has a low safety factor,making it difficult to meet on-site needs.The segmented replacement method,on the other hand,does not require support and is easy to construct,making it a good candidate for application.However,there is a stress lag issue,causing the axial compression ratio of the first replaced area of the shear wall to be higher than the design value,which does not meet the mandatory provisions of the seismic code.Therefore,studying the stress lag issue during the segmented replacement of high-rise building shear walls,and obtaining the applicable range of floors for segmented replacement methods,is of great significance for ensuring the safety of high-rise building construction.In this paper,a modified theoretical model for multi-vertical rod units was proposed to describe the shear stiffness of walls by attaching shear springs to vertical rod units,which is suitable for unsupported segmented replacement of shear walls.The modified theoretical model was converted into a computable program model using MATLAB to verify its accuracy and efficiency.Based on the modified theoretical model of multi-vertical rod units,a study was conducted on the stress lag phenomenon after the reinforcement of shear walls using the replacement method.The main work and results are as follows:(1)A modified model for multi-vertical rod units suitable for unsupported segmented replacement was proposed and its accuracy and efficiency were verified.The shear stiffness of the wall was described by attaching shear springs to the vertical rod units of the multivertical rod unit model,and a modified theoretical model for unsupported segmented replacement of multi-vertical rod units was proposed.The calculation program of the model was established in MATLAB,and the stress changes during the segmented replacement process of the shear wall were simulated and compared with the microscopic entity unit model,verifying the accuracy and efficiency of the modified model for multi-vertical rod units.(2)The effectiveness of the modified model for multi-vertical rod units was verified through on-site experiments,and the impact of initial overlying floor loads on the stress of the wall during the replacement process was studied based on the model.As the initial load increases,the vertical stress increases almost linearly,and the growth rate is related to the sequence of wall segment replacement.(3)The stress lag coefficient kij was proposed to describe the degree of stress lag between wall segments replaced in different batches.Using this coefficient,the impact of changes in overlying floor loads after replacement on the stress lag effect was further studied qualitatively and quantitatively.The study found that when the overlying load was increased after the replacement was completed,the vertical stress growth rate of each wall segment was different,but the degree of stress lag decreased and was closely related to the sequence and relative position of wall segment replacement.Finally,based on a model that corrects for multiple vertical bar units,a method for determining the feasibility of using segmented shear wall displacement reinforcement is proposed.