Research On The Technology Of Strengthening High-rise Shear Wall Structure With Braceless Replacement Of Concrete

The replacement concrete reinforcement method is often used to solve the problem of low concrete strength or serious defects.In the method,the support-free replacement concrete reinforcement method is used in the shear wall structure reinforcement project due to the short construction period,no need to unload supports,and low cost.There are still few studies on this technology in the design of the scheme and the changes in the wall stress during the construction process.Based on the research background of a shear wall structure project in Xianyang City,Shaanxi Province,this paper compares and analyzes the strength reduction of the twentieth-storey shear wall of the structure and the seismic performance and bearing capacity of the design strength.Combining the current situation of the project,it chooses non-support replacement concrete reinforcement Method,design reinforcement plan,discuss construction technology,construction monitoring,and use ETBAS finite element software to simulate the whole process of support-free replacement concrete reinforcement construction,and analyze the changes in shear wall stress and the stress of each batch of replacement wall limbs in the process of replacing concrete The law and the impact of the replacement construction process on the shear walls of other floors.The main research results and contents of this paper include:1.ETABS was used to establish the overall model of the original structure and the overall model in which the strength of the twentieth-story concrete was reduced from C30 to C20.The results of modal analysis and response spectrum analysis showed that the decrease of concrete strength resulted in the increase of structural period,inter-story displacement and inter-story displacement angle.Large,the displacement angle of some floors of the structure under the action of the X-direction earthquake exceeds the specification limit;The calculation results of the axial compression ratio of the twentieth-story shear wall before and after the reduction of concrete strength show that the reduction of concrete strength causes the axial compression ratio of the shear wall to increase by 1.5 to 1.7 times,and the axial compression ratio of some shear walls exceeds the specification limit.It can be seen that the reduction of concrete strength leads to the reduction of the overall seismic performance and bearing capacity of the structure.Reinforcing only the shear wall whose axial compression ratio exceeds the limit can make it meet the specification limit,but it cannot solve the problem of the interlayer displacement angle caused by the decrease of concrete strength exceeding the specification limit.Therefore,combined with the current structure research in this paper,the alternative support-free replacement concrete reinforcement method is selected after a comparison of alternatives.2.Two replacement schemes of the second batch and the third batch were designed with the axial compression ratio as the control condition.The simulation analysis of the axial compression ratio of the two options showed that the axial compression ratio of the wall limbs during the three-batch replacement process was less than that of the second batch.After comparative analysis,the three-batch replacement plan was selected,and the auxiliary support system in the reinforcement construction process was designed,and key technologies such as construction technology and construction monitoring were summarized.3.The non-linear sequential construction loading of ETBAS software was used to carry out finite element analysis on the whole construction process of support-free replacement concrete.The results showed that: during the replacement construction process,there is a stress hysteresis phenomenon in the wall limbs replaced in each batch;in the normal use stage after the replacement is completed,The wall limbs replaced by each batch can be stressed together;the impact of the replacement construction process on the stress distribution of the structure is mainly concentrated on the shear walls of the upper and lower floors adjacent to the replacement layer,and the stress on the end wall limbs is greater,even As a result,tensile stress appears at the end of the upper shear wall connected to the replacement layer,so corresponding measures should be taken during the replacement plan design and replacement construction process.