Progressive Collapse Behavior Studies Of Multi-Storey Steel Frame Structures Based On Vector Form Intrinsic Finite Element Method

The progressive collapse of building structures is a hot research topic at home and abroad.The progressive collapse of building structures is a dynamic process from continuous to discontinuous.This process involves geometry,material and contact three nonlinear.The existing explicit finite element method,the implicit finite element method and the discrete element method and other numerical methods have some limitations in the analysis of progressive collapse behavior of structures.Vector Form Intrinsic Finite Element(VFIFE)is a new numerical analytical method based on vector mechanics and point value description.This method has some advantages in solving the problems of structural nonlinear discontinuity,such as large deformation,large displacement,fracture and collision,and the dynamic prediction of mechanism.In this paper,the difficulties of progressive collapse and the advantages of vector finite element method are discussed,the method of using VFIFE to study the progressive collapse behavior of steel frame structures is presented.It provides a new idea and method for the deep understanding of the progressive collapse mode and failure mechanism.In this paper,the VFIFE as a tool,combines the classical methods and ideas of progressive collapse.In this paper,the progressive collapse behavior of the steel frame is studied from three aspects: the resistance mechanism,the dynamic nonlinear analysis and the numerical simulation of component fracture.The main research content is as follows.(1)Comparative the difficulties in the calculation of structural collapse by using the numerical methods,such as explicit finite element method,implicit finite element method and discrete element method.This paper introduces the characteristics of vector finite element,and points out that it has an advantage in studying the progressive collapse of structures by using VFIFE.This paper systematically expounds the basic theory of vector finite element method and derives the energy calculation method.The correctness of the proposed method is verified by energy conservation.(2)The VFIFE is applied to the progressive collapse Pushdown analysis for the first time.It takes into account the complex problems of Pushdown analysis,such as large rotation and elastic plasticity,structure and mechanism transformation.It obtained the axial force and bending moment of the law,the load coefficient vertical displacement curve and the strain energy curve.In this paper,the formation mechanism and evolution process of bending resistance and catenary action are studied,the displacement,axial force,bending moment and strain energy of the remaining structure are analyzed.(3)The VFIFE is used as a tool to implement the transient loading method.And the method is used to remove the bottom column of steel frame.At the same time,the internal force change index and strain energy change index are proposed.the influence area of the dynamic effect and redistribution of internal force caused by the unbalanced load is studied.In addition,the dynamic response of the upper floor column is discussed.(4)According to the basic theory of VFIFE,the numerical analysis model of plane steel frame and space steel frame is established.The fracture criterion and fracture mode of component failure are given.A MATLAB program is developed to simulate the fracture process of steel frame structures in the process of progressive collapse.This program can be used to track and predict the collapse behavior of the remaining structure.The collapse mode and failure mechanism of steel frame structures are studied.