【作者】 喻莹；

【导师】 罗尧治；

【作者基本信息】 浙江大学 ， 结构工程， 2010， 博士

【摘要】 本文以空间钢结构的连续倒塌破坏研究为主线,以向量式结构力学为理论基础,以有限质点法为手段,分别从几何破坏、材料破坏、构件断裂以及接触碰撞四个方面,通过理论推导和数值计算,对空间钢结构连续倒塌的全过程进行模拟,并对结构连续倒塌过程中的破坏机理进行研究。基于向量式结构和固体力学理论,本文提出了一种结构分析的新方法——有限质点法。该方法以“点值描述”和“路径单元”为基本概念,以清晰的物理模型和质点运动控制方程描述结构行为,在结构的几何非线性、材料非线性以及不连续行为计算中有很大的优势。文中详细阐述了有限质点法的基本概念和原理,推导了该方法进行空间杆系结构和空间梁系结构的基本公式,以及结构中典型约束点及特殊运动点的内力计算公式,为空间钢结构连续倒塌研究奠定了理论基础,提供了分析方法。建立了有限质点法进行结构几何非线性动力分析的基本框架,对空间钢结构的几何破坏问题进行了研究。首先验证了有限质点法在空间杆系和梁系结构几何非线性动、静力问题求解中的有效性,然后在此基础上对空间钢结构几何破坏中的两种典型破坏模式—失稳破坏和机构化破坏—进行模拟和分析。探讨了空间钢结构弹性失稳破坏的全过程跟踪方法,以及结构的失稳破坏机理。针对空间钢结构的机构化破坏问题,讨论了结构的体系分类。验证了有限质点法在动不定结构运动行为模拟中的有效性,并对空间钢结构的机构化破坏过程进行了分析。发展了有限质点法进行结构弹塑性分析的基本流程,对空间钢结构的材料破坏进行了研究。建立了结构的弹塑性模型和单元屈服方程,通过对若干杆系和梁系结构的弹塑性分析,验证了有限质点法在结构弹塑性分析中的有效性。在考虑压杆失稳模型的基础上,分析结构的弹塑性失稳过程,研究了不同的本构模型对结构失稳模式的影响。为分析空间钢结构的动力弹塑性行为,建立了弹塑性模型加卸载过程中的应力判断准则和计算流程,对空间钢结构往复荷载下的滞回性能进行了模拟和分析。提出了构件断裂的模拟算法,对空间钢结构构件的断裂行为进行了研究。基于材料试验和文献资料,建立了结构构件的断裂准则和断裂模式,给出了断裂发生后质点内力、外力、质量等的计算方法。从能量分析的角度出发,通过对若干数值算例的分析验证了断裂算法的合理性。结合结构的几何和材料非线性分析,对空间钢结构的断裂过程进行了分析。提出了构件接触和碰撞模拟算法,对空间钢结构构件的接触和碰撞行为进行了研究。文中基于空间向量分析理论提出了结构空间运动中的接触侦测方法,然后根据碰撞类型的不同,分别建立了结构刚性体碰撞和柔性体碰撞模型,推导了有限质点法中结构碰撞反应的计算公式。通过对典型算例的分析,验证了结构接触侦测算法的准确性和结构碰撞反应算法的有效性。综合以上各部分的分析和程序成果,以某空间悬挑网架在台风下的连续倒塌破坏为例,分别采用杆单元和梁单元对该结构在动荷载下的连续倒塌全过程进行逐步分析。通过将计算结果与现场破坏情形进行对比,验证了有限质点法在结构复杂行为分析中的有效性,也深入了解了该结构的连续倒塌破坏机理。本文的研究工作模拟了空间钢结构的连续倒塌破坏的全过程,揭示了倒塌过程中的破坏机理,推进了空间钢结构连续倒塌研究的发展。同时,有限质点法的提出为工程师和研究者进行结构的复杂行为分析提供了新的方法和思路,具有一定的指导意义。更多还原

【Abstract】 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.更多还原