Seismic Analysis Of Shear Wall Structure Reinforced By Partial Replacement Reinforcement Method During Construction

The cast-in-place concrete shear wall structure is a common structural form in high-rise buildings.The building structure may fail to meet the reliability requirements due to design,construction and use reasons or the influence of natural factors such as fire and earthquake.In order to eliminate the hidden danger of structure safety and meet the requirements of normal use,the reinforcement treatment of existing buildings has become a common engineering and technical subject.Local reinforcement replacement method is a preliminary exploration on the basis of replacement reinforcement method.Compared with the traditional replacement method,the local reinforcement replacement method only uses high-strength materials to dismantle and replace part of the component,and the retained part can be used as the construction support system,which not only saves manpower and material resources,but also reduces the construction period.This paper is an exploratory research,which can provide reference for future academic research and engineering practice.In this paper,the shear wall in a high-rise concrete shear wall structure under construction in a city of Jiangxi Province（the construction to the 10th floor found that the concrete strength of the partial shear wall at the bottom of the 1-3 floors was low and the bearing capacity was insufficient）was taken as the research object,and the reinforcement treatment was carried out by local reinforcement replacement method.The main research contents are as follows:Based on the theory of three-dimensional virtual laminated element with solid degradation,a nonlinear finite element analysis program for shear wall structures with local reinforcement displacement method is developed,which can consider the construction process.The analysis program can calculate the structure in stages according to the construction procedures such as partial demolition and partial reinforcement replacement,and strictly consider the influence of the initial state information of each stage（including internal force,displacement,cumulative plastic strain or material damage）on the force of the structure in the next stage,so as to realize the simulation of the construction process of reinforcement.The dual nonlinearity（geometric nonlinearity and material nonlinearity）is taken into account in each stage,and the three-dimensional space cooperative simulation analysis of beam,slab and wall can be realized.With the help of the above program,for a single shear wall,the variation of displacement and stress of L-shaped shear wall in different displacement areas with loading is studied under different strength grades of substituted concrete（C50,C60,C70）and the initial stress level of the original shear wall structure(0.4f_c0,0.5 f_c0,0.6f_c0)（a total of 9 groups of models）.The application scope of local reinforced displacement method is summarized.According to the results of the finite element analysis,there will be a certain stress difference in each area of the existing shear wall after the completion of the local reinforcement and replacement method.However,with the subsequent construction and use,the stress and strain in each area of the displaced shear wall will be redistributed,so that the new and old concrete can work together well.At the same time,due to the continuous stress redistribution in the replacement area,the strength utilization coefficient can not be properly controlled.By observing the stress situation in the final replacement area,it can be seen that the higher the initial stress level is,the lower the strength utilization coefficient of concrete in the replacement area.The higher the strength grade of displacement concrete is,the lower the strength utilization coefficient of displacement concrete is.Local strengthening displacement method can be used for the situation of insufficient concrete strength.When the initial stress level exceeds0.73,it is not recommended to use this method because too many cracks are produced during the displacement construction,and even three-way cracking occurs.At the same time in the overall structure（structure,18 floors,the total number of layer has construction to 10 layers,three layers at the bottom of the part of the shear wall local reinforcement replacement method is used to reinforce）,according to the SATWE elastic module algorithm of wall limb axial pressure ratio results,determine the 24 simulation working condition of the construction,the strength does not meet the requirements of the shear wall partial areas to strengthen the substitution.In order to verify the effectiveness of the local reinforcement replacement method,the deformation and load-bearing conditions of 15 shear walls at different locations in different areas（including displacement area and non-displacement area）during the replacement process and the subsequent construction and loading stage,as well as the load-bearing and deformation conditions of the reinforced structure under the simulated force of horizontal static pushover were studied.The results of finite element analysis show that the strength utilization coefficient of different displacement areas is not the same in the whole structure due to the effect of the replacement sequence.Generally,the strength utilization coefficient of the area completed by replacement first is high,and the strength utilization coefficient of the area completed by replacement later is low.In the whole structure,the vertical component is not uniformly stressed,and the bending moment is inevitable.Therefore,in the actual project,the replacement area and replacement order should be strictly controlled,and the larger part of the force should be regarded as the key replacement area.The bearing capacity and anti-deformation ability of the structure are improved by local reinforcement replacement method,which can meet the safety requirements of the original structure design and the requirements of building use.