Research On Force Behavior Analysis Of Intersecting Connection Of Square CFST Diagrid Structures By Multi-scale Modeling

Diagrid structural system is an innovative structural system.Because of its unique structural features and beautiful architectural appearance,more and more diagrid structural system are widely used in the structure of modern architecture.Studies have shown that the concrete filled steel tubular(CFST)diagrid structures are mainly composed of larger axial force,the compressive behavior of the intersecting connection is unclear which the force of the four pillar of oblique confluence is relatively complex.Based on the conclusion of an amount of domestic and foreign references literature and summarizing the present experimental and theoretical research,the compressive behavior and parametric analysis of the square CFST was studies under the monotonic load and cyclic load by nolinear finite element analysis(FEA).Including the following aspects:(1)The mechanical performance of the CFST intersecting connection under axial compression load was analyzed by nonlinear elasto-plastic finite element.The analytical results agreed well with experimental results.For calculation load versus displacement curves of A and B types of square CFST intersecting connection,the general purpose FEM software ABAQUS with concrete damage plastic model was used.Stress variation of steel tube,core concrete,vertical connection plate,reinforcement ring plate,lining plate in the process of axial loading and the change of component damage location are analyzed in order to further clear about the working mechanism of intersecting connection.(2)The multi-scale model was established,and then was proved to be valid through comparisons with test.The results show that it can be accomplished the fine transition between different scales of the model by the macro model and micro model such as shell element,entities element.Then the nonlinear analysis was conducted on the intersecting connection under the repeated displacement loadings,and the hysteresis curve and skeleton curve was obtained.On the basis of the curve,stiffness degradation rules are studied.(3)Parametric study of load to displacement curves of square CFST intersecting connection multi-scale finite element model were carried out based on the analytical methods in this paper.Skew angels,thickness of steel tube,vertical connection plate,ring reinforcing plate,linging plate,concrete strength,and steel strength,were all considered as analysis parameters.