Research On The Distribution Of Axial Force And Elastoplastic Performances Of Inclined Columns Of CFST Diagrid Structures

Diagrid structures is different from the traditional structural systems,the good space performance and beautiful exterior make the application of this structure is widely used.The internal force of the inclined column is mainly composed of the axial tension and compression force,which can effectively utilize the mechanical properties of the component to provide a strong anti-lateral stiffness,so as to become the key component of the bearing capacity of the whole structure.Therefore,the distribution of the axial force of the inclined column under various load conditions is the cornerstone for studying the mechanical properties of the whole structure.Based on an actual engineering case,the structure model of CFST diagrid structures is established,and the distribution of axial force of inclined column under both static and dynamic load is analyzed at the structural level.On the basis of analysis results,the axial hysteretic behavior of concrete-filled steel tubular column and its influence factors are studied from the perspective of components.Finally,the seismic vulnerability assessment of the model is carried out according to IDA method.The main contents are as follows:(1)Based on the engineering reality,the structural design software Etabs was used to establish the elastic model of CFST Diagrid Structure.And the axial force distribution of the inclined column is discussed under the vertical,lateral load and combination of both vertical and lateral loads.Based on the fiber cross section model,Perform-3D is used to analyze the elastic modulus of the structural model and the dynamic elasto-plastic time history analysis.The distribution of the axial force of the inclined column in the process of static pushover is analyzed,and the plastic development process of the outer cylinder is clarified.At the same time,the axial force distribution of the inclined column under different ground motion is analyzed.In addition,the axial deformation ratio and the internal force ratio are obtained from the symmetrical inclined column,which are corresponding to the same inclined column under reciprocating push,and provides the accordance for the loading system in the next component analysis.(2)Based on the solid element,the finite element soft ABAQUS was used to establish the concrete-filled steel tubular column model with different parameters.According to the aforementioned deformation ratio of the inclined column,the loading system of the component is determined,and the force performance under the cyclic tension and compression load is analyzed,and the stress distribution?damage and the working mechanism of steel pipe and core concrete in different stages are clarified.The axial hysteretic behavior of the component is analyzed by parametric analysis including different diameter-thick ratio,material strength,sectional steel ratio and loading systems.The key factors affecting the axial hysteretic behavior are clarified.(3)Based on the IDA method,the elasto-plastic time-history analysis of the CFST diagrid structures is analyzed.Ten ground motion records are selected to analyze the structural seismic response,and then combined with the performance level limit of our seismic code requirements,the corresponding seismic vulnerability curve is established.The seismic vulnerability of the model is evaluated based on the analysis results.