Progressive Collapse Studies Of Self-centering Energy Dissipation Braces Steel Frames Based On Vector Form Intrinsic Finite Element Method

Progressive collapse caused by damage and failure of key members of building structures has become an area of wide concern for designers and researchers.Because the structures will undergo obvious deformation during the progressive collapse of the structures,and this process is accompanied by nonlinear behaviors such as vibration,fracture,and collision.The efficiency of progressive collapse analysis and simulation of complex structures using traditional finite element software is limited.Vector form intrinsic finite element has great advantages in solving complex problems such as large deformations,collapses,and collisions of structures and mechanisms.In the seismic design process,self-centering energy dissipation braces can effectively control the residual deformation of the structure and dissipate the seismic energy.Self-centering energy dissipation braces can not only effectively control the residual deformation of the structure,but also dissipate the seismic input energy.The vertical progressive collapse of the structure and the structural vibration response under the earthquake have common characteristics.It is obvious that the self-centering energy dissipation braces also has a positive effect on the progressive collapse.This paper is based on the basic principles of space vector form intrinsic finite element.In this paper,a numerical analysis of the fracture and collision phenomena of space framed structures is carried out.The nonlinear dynamic analysis method and the transient unloading method were used to perform horizontal seismic time history analysis and vertical progressive collapse time history analysis of the steel frame with self-centering energy dissipation braces under different parameter settings to explore the best parameters of self-centering energy dissipation braces in both modes.The main research contents are as follows:First,it introduces the main analysis ideas of the space vector form intrinsic finite element method in dealing with strong nonlinear behaviors such as large structural deformations,mechanism motions,fractures and collisions.The basic theory and calculation process of the space beam frames unit are described in detail.The restoring force model of self-centering energy dissipation braces suitable for vector form intrinsic finite element method is established.With reference to the braces design method based on the stiffness ratio,the analysis process of the three main parameters of self-centering energy dissipation braces is drawn up,and the calculation sample is designed and the program is verified.The vector form intrinsic finite element method has been used to carry out the horizontal seismic time history analysis of the unbraced steel frame and the braced frame with different parameters.Finally,multiple indicators such as displacement,internal force,and energy consumption are comprehensively considered to study the energy dissipation and seismic mitigation effect of self-centering energy dissipation braces under different parameter combinations.The instantaneous unloading method was used to simulate the failure of the bottom column of the frame.The vector finite element method was used to analyze the vertical nonlinear dynamic time history of the two stages before and after the failure of the column.The same example and the combination of brace parameters as in the foregoing are used to perform the vertical nonlinear dynamic analysis of the self-centering energy dissipation braces frame.In this part,the effect of supporting different parameter combinations on the structure’s resistance to progressive collapse are compared and studied.This part optimizes the fracture criterion and fracture mode,formulates and introduces in detail the implementation process of the two parts of contact algorithm and collision response,and verifies the reliability of the whole process simulation platform of the spatial frame structure fracture and collision phenomenon based on the vector form intrinsic finite element method.Finally,the progressive collapse process of the structure with parametric and visualization functions after removing vertical load-bearing members was simulated,and the effect of adding self-centering energy dissipation braces on the progressive collapse process of the steel frame was studied.