Progressive Collapse Of Space Steel Structures Based On The Finite Particle Method

Based on the Finite Particle Method (FPM), this thesis carries out an intensive research regarding the simulation and analysis of progressive collapse for space steel structures. Not only nonlinear geometric and constitutive behaviors, but also fracture, contact and collide during the dynamic process of progressive collapse are taken into considerations in the research.This thesis presents a structural analysis method called the Finite Particle Method (FPM) for structural progressive collapse simulation. Different from the traditional methods generated from continuum mechanics and variational principle, the FPM is based on the vector mechanics. With the description of "point value" and "path element", the FPM models the analyzed domain composed of finite particles whose motions are described by Newton's second law. Structural nonlinearities and discontinuities can be easily handled by this method, which is very advantageous in the simulation of structural failure. This work derives fundamentals of the FPM, including basic procedures, formulations of 3D bar element,3D beam element and internal force of particles containing special motion restrictions. The FPM is the basic method used in this work.The framework of dynamic geometric nonlinear analysis of the FPM is developed, and analyses of geometric failure of space steel structures are presented. With several numerical examples, the accuracy and generability of the dynamic geometric nonlinear analysis program is demonstrated. Then, two kinds of typical geometric failures, buckling and mechanism failure, are simulated and analyzed. Different strategies for pre-and post-buckling simulation are given and discussed, which are successfully applied in the analysis of elastic buckling of space steel structures. The FPM is also verified in the motion analysis of kinematically indeterminate structures. Taking a double-layer grid structure as an example, the mechanism failure procedure of space steel structure is investigated.The framework of elastic-plastic analysis based on the FPM is developed, and analyses of material failure of space steel structures are presented. The elastic-plastic model and yield equations of steel material are proposed. Several numerical examples are presented to prove the availability of the FPM in structural material failure analysis. And then the inelastic post-buckling behavior of space steel structures are compared and discussed with different constitutive models. Based on the stress incremental formulation and stress reversal model, hysteretic behavior of a double layer grid structure under cyclic loading is analyzed, which reveals the energy dissipation capability of space steel structures. The algorithm considering structural member fracture during progressive collapse process is developed. Based on concepts of the FPM, the failure criterion and the failure modeling algorithm are proposed, respectively. According to the energy conservation study of a 2D truss, different kinds of energies are balanced during the fracture process, which verified the fracture algorithm in this work. Combining the nonlinearity analysis, fracture behaviors of several space steel structures are investigated.The algorithms considering contact between structural members during the progressive collapse process are developed. The algorithm of contact determination is proposed based on the theory of 3D analytical geometry. According to different collide styles between members, the formulations of rigid and flexible collide are derived, respectively. Several numerical examples are presented to demonstrate the accuracy and capability of the contact algorithms.The whole progressive collapse process of a cantilever steel structure is simulated and investigated using the programs developed in this work, providing more profound understanding of structural failure reasons.This study advances the development of investigations of progressive collapse for space steel structures, and provides a basis for the further researches in this field. Meanwhile, it also promotes the applications of the Finite Particle Method into complicated structural behavior analysis.