Study On The Design Method Of Improving The Deformability Of Mid-Rise SRC Shear Walls With Rectangular Steel Tubes

The mid-rise SRC shear wall is widely used in practical engineering.The small ultimate deformability under lateral loads is the main problem in engineering applications.Especially under high axial compression,it is difficult to meet the relevant requirements of codes.Many researchers proposed lots of measures to improve the ultimate deformability of mid-rise SRC shear walls.Most of the measures can effectively improve the ultimate deformability of walls,but due to the complicated construction process,which makes them difficult to be widely used in engineering.Team's previous experiments showed that rectangular steel tubes at the bottom of concealed columns of mid-rise SRC shear walls can confine the boundary concrete and improve the ultimate deformability of walls effectively.However,experiments can only qualitatively reflected the improvement effect of rectangular steel tubes on the ultimate deformability of mid-rise SRC shear walls due to the lack of experiments.So the experiments can't give a reference design method for practical engineering.Based on the experimental results,in this paper,the finite element model of SRC shear walls with rectangular steel tubes was established using ABAUQS software.The whole process behavior of SRC shear walls under monotonic lateral loading was simulated to research the application scope of the steel tube.Otherwise,the influence of height,width and cross section structures of the steel tube to the deformation of shear wall was also studied.Further,a specific design method of the steel tube was proposed to give a reference for practical engineering.The main works and conclusions of this article are as follows:(1)Six rectangle steel tube confined concrete columns were investigated experimentally under axial compression.Based on the experiment results,a method to calculate the effective transverse confined stress provided by the rectangle steel tube was proposed through combining finite element simulation analysis.Furthermore,a model to determinate the stress-strain relationship of rectangle steel tube confined concrete under axial compression was put forward reference to the Mander's model.This model can accurately reflect the confinement effect of steel tubes on concrete and can be used in the simulation of mid-rise SRC shear walls with rectangular steel tubes.(2)A finite element model of the SRC shear wall was established using ABAQUS.Comparison with the test results showed that the model can accurately predict the main characteristics of the SRC shear wall with and without steel tubes,such as load-displacement curves and failure patterns.Analysis showed that the mid-rise SRC shear wall has strongly shear deformation,so the flat section assumption should not be used to analyze the deformation of mid-rise SRC shear walls.(3)The application scope of steel tube was determined through analyzing parameters influencing the failure pattern of the SRC shear wall.The results showed that the shear span ratio and steel ratio of the concealed column are the main factors influencing the failure pattern of SRC shear wall.The failure pattern of SRC the shear wall with low shear span ratio and high steel ratio is the web shear-compression failure firstly.The rectangular steel tubes is only suitable for the wall with flexural failure or flexural-shear failure but dominated by flexural,not for that kind of walls occurring shear-compression failure.(4)The design suggestions of the height,width and own construction of the steel tube were proposed by studying the design method of the steel tube.The research results showed that in order to ensure the steel tube can effectively confine the concrete,the construction and width-thickness ratio of cross section of the steel tube should consult the relevant provisions of the technical specification for structures with concrete-filled rectangular steel tube members.In order to avoid failure of the concrete at the top of the steel tube,the height of the steel tube should meet the lowest limit,which was influenced by the width of the steel tube,shear span ratio and axial compression ratio.The width of the steel tube should consult the horizontal length of the confined boundary member of the code for seismic design of buildings.