Study On Strengthening Method Of Unsupported And Whole Story Replacement Shear Wall Concrete

With the acceleration of urbanization in China,more and more high-rise buildings are springing up.Reinforced concrete shear wall structure is widely used in high-rise buildings because of its good integrity,stiffness and seismic performance.In the process of construction,due to the short construction period,various processes,fast construction speed,engineering quality accidents often occur.It is a common engineering quality accident that the concrete strength of a certain layer or several layers of shear wall is far lower than the design requirements after construction or completion of many layers.How to deal with this engineering quality problem is an urgent problem for structural engineers.In order to reduce the loss,partial replacement or whole layer replacement has become the best choice.Based on the fact that the strength of the first whole floor concrete of a residential building with reinforced concrete shear wall structure under construction is far lower than the design strength,according to the actual situation of the site,this paper has formulated the reinforcement scheme of the whole floor concrete replacement without support.According to the construction characteristics of the whole floor replacement in sections and batches,Midas is used Gen finite element software establishes the finite element calculation model for each stage of replacement reinforcement and subsequent floor construction,calculates each stage of replacement concrete,analyzes the change rule of vertical stress of two batches of shear wall sections in replacement floor and the change rule of vertical stress difference of two batches of shear wall sections,and puts forward the improvement method for the situation that the vertical stress difference of two batches of shear wall sections is large The main conclusions are as follows:(1)The initial stress level of each shear wall in the replacement layer is different before replacement,but the change trend of the vertical stress of the first and the second batch of wall sections of each shear wall is the same.(2)After the first batch of unqualified concrete wall segments are chiseled out,the load transmitted from the upper part of each shear wall basically remains unchanged,while the vertical load of each shear wall changes from two batches of wall segments to only the second batch of unqualified concrete wall segments,and the vertical compressive stress of the second batch of unqualified concrete wall segments surges;the first batch of new concrete wall segments are poured and reach the design strength After that,the vertical compressive stress of the second batch of unqualified concrete wall sections decreased slightly,and that of the first batch of new concrete wall sections increased slightly.(3)After chiseling the second batch of unqualified concrete wall sections,the vertical compressive stress of the first batch of new concrete wall sections increased sharply;after pouring the second batch of new concrete wall sections and reaching the design strength,the vertical compressive stress of the first batch of new concrete wall sections decreased slightly,and the vertical compressive stress of the second batch of new concrete wall sections increased slightly.(4)From the completion of replacement and reinforcement to the completion of all subsequent floors,the average value of the vertical stress difference reduction of the first batch and the second batch of new concrete wall sections in the replacement floor is about 13%,because the creep characteristics of concrete reduce the vertical stress difference of the first batch and the second batch of new concrete wall sections,making the vertical stress redistribution of the section.(5)In the scheme design of segment and batch,increasing the proportion of section area of the first batch of wall sections and reducing the proportion of section area of the second batch of wall sections can reduce the average vertical stress of the first new concrete wall section after the completion of replacement,and the vertical stress difference of the two batches of wall sections will also decrease;when pouring the first batch of new concrete,increasing the section area of the first batch of new concrete wall sections along the wall thickness The surface area,after the strength of each batch of concrete meets the requirements,Chisel out the increased part of concrete.This construction method can adjust the vertical stress difference of the first batch and the second batch of new concrete wall sections by changing and increasing the section area of the first batch of new concrete wall sections.