Mechanical Performance Analysis Of Bottom Walls Leg Of Frame-core Tube Structure

In recent years,rapid economic development has promoted the modernization of the city,and the height of the building has been constantly refreshed.The wall leg at the bottom of the high-rise building,the axial tensile force generated by the overturning bending moment under the earthquake action may still be in a tensile state after removing the self-weight load and additional load of the structure.At this time,the stress state of the wall member is more complicated,and the tensile shear and compression shear alternately accelerate the destruction,which has an adverse effect on the seismic performance and safety of the structure.What kind of structural form is adopted or which components are added to the structure to reduce the risk that the outermost shear wall is vulnerable to tensile cracking under the action of fortification earthquake,and whether the shear wall must be "Technical Points for Review".There is still a non-negligible controversy over the addition of tensile steel to control the nominal tensile stress of concrete.Based on the newly completed frame-core tube building in Jinzhong,Shanxi Province,this paper analyzes the mechanical performance of the bottom wall legs,studies its impact on the seismic performance of the overall structure,and draws the following conclusions:(1)Use SAP2000 software to change the structure of the reinforced layer under the given number of reinforced layers and specific reinforced layer position,and use the equivalent elasticity method to analyze the response spectrum.The simulation analysis results show that: for structures with different reinforcement layers,the maximum axial tensile force that the bottom wall legs outside the core tube may be subjected to fortified earthquakes has been reduced to varying degrees;waist truss or outrigger truss with the same linear stiffness are set separately The beneficial effects on the bottom wall limbs are quite similar;the shear force and bending moment of the bottom wall limbs have not changed greatly due to the different forms of the reinforcement layer.When the core tube wall limb is under tension in the model,the acting force on the wall limb at the corners and connecting parts on the same axis is always greater than the wall limb in the middle position.(2)Based on "Technical Essentials",the basic model B was used to establish a model F with additional tensile steel at the bottom and a model E to replace the tensile steel with other strengths such as steel bars.Through elastic time history analysis and elastoplastic time history analysis,it is concluded that due to the difference in materials and dosage of the bottom legs of the two models,the stress of each part of the component is different,and the stress between the floors is smoothly transitioned and evenly distributed.And the model of replacing the equal strength with steel bars will not affect the overall stability and lateral stiffness of the structure.Therefore,it is recommended not to use the nominal tensile stress of concrete as a sufficient condition for adding tensile steel under the action of earthquake prevention,and to analyze whether to add steel according to the actual situation and specific analysis.