Analysis Of Stress Hysteresis Effect Of Reinforced Concrete Shear Wall Structure By The Concrete-replacing Method Without Support

The replacement concrete reinforcement method is a commonly used reinforcement method which can solve the problem that the strength of concrete is low and the concrete has serious defects.In the high-rise concrete shear wall structure,when we need to replace the concrete of the shear wall at the bottom of the floor,the support of the replacement of the construction is very difficult,costly,and there are security risks.The concrete-replacing method without support can solve this problem,but the stress hysteresis may cause the actual axial compression ratio of the shear wall of the first displacement zone is significantly higher than the original axial compression ratio,which does not satisfy the provisions of seismic specification.Although there are many engineering applications for the concrete-replacing method without support,but the problem of stress lag is still lack of research.Combining with a project of unsupported replacement shear wall concrete in a housing estate of Yancheng.This paper introduces the technology of reinforced concrete reinforcement without support,and summarizes the key construction techniques such as temporary support of local beam boards,removal of shear wall concrete,reinforcement finishing,pouring of new concrete and monitoring of construction process.It analyzes the variation law of the vertical stress of the replacement wall itself with the construction,the range of the stress redistribution during the construction process,the variation law of the stress hysteresis degree and the optimization scheme of technology of unsupported replacement shear wall concrete.This paper puts forward the relevant empirical formula based on the calculation of engineering design software,and it guides the design of the concrete-replacing method of shear wall without support.The combination of finite element simulation analysis and field measurement is an effective method to study engineering problems.In this paper,the finite element method is used to simulate the whole construction process.In order to simulate the chisel of the old concrete and the pouring of the new concrete,the "kill" and "activate" commands of the "birth-death element method" are used.Through the finite element simulation,the variation law of the vertical strain values between the one-batch and the two-batch replacement wall in each construction stage are obtained.The results are compared with the actual construction monitoring results.It is found that the wall strain is similar to the result of the actual measurement with the change of the construction step,and the numerical value is also close.It indicates that the construction simulation method is feasible,and matches the true situation.Through the finite element simulation analysis,the results show that there is a vertical stress hysteresis in the replacement wall in the no-support replacement shear wall concrete reinforcement project.After the walls are replaced,there is always stress difference between the sections of the walls.The stress redistribution caused by the replacement construction mainly takes place on the upper layer and the next layer.When the sections of the walls are removed,there is the tensile stress on the lower part of the corresponding upper wall.lt is easy to cause cracking.We need to pay close attention to it.The vertical stress difference between the first batch and the second batch of the replacement wall increases linearly with the increase in the upper load when the displacement occurs.The degree of stress hysteresis in the post-replacement sections of the walls is also increased linearly with the increase of the upper load at the time of replacement.With the increase of the number of batch of replacement wall,and the vertical stress of the replacement wall is the smaller,and the stress difference between the batches is the smaller,and it can optimize the scheme of technology of unsupported replacement shear wall concrete.