【作者】 侯艳丽；

【导师】 张楚汉；

【作者基本信息】 清华大学 ， 水利工程， 2005， 博士

【摘要】 本文研究结构从小变形损伤断裂到大变形渐进破坏的全过程仿真分析方法,期望实现从连续介质到非连续介质转化的数值模拟。据此,本文系统研究并初步实现了变形体离散单元法与弥散裂缝模型和分离裂缝模型两种非线性断裂力学模型的耦合,并应用于混凝土高坝的断裂与破坏过程的工程分析中,主要研究内容包括:1.以三维刚体离散元为基础,采用在数值模型和实际结构之间建立的刚度等效、强度等效和荷载等效的原则,形成连续-非连续介质的统一模型——刚体弹簧元。应用这一方法研究了竖向横缝和水平施工缝等弱面组成的拱坝在强震条件下的整体性受损情况和破损机理。2.提出了三维变形体离散元模拟连续介质和非连续介质时的分离界面刚度选取准则。应用三维变形体离散元对梅花拱坝沿坝基的上滑失稳溃决问题进行了仿真计算;指出在沿拱坝建基面存在不利的软弱面结构与两岸坝坡平缓时,需要认真研究拱坝沿坝基的上滑失稳问题,在拱坝设计中进行相应的稳定校核。3.基于钝断裂带理论,推导了两种不同的非线性弥散断裂力学模型——固定裂缝模型和旋转裂缝模型的应力应变全量关系描述,将准脆性材料的开裂模型嵌入到变形体离散单元法的块体本构模型中,提出一种将损伤断裂模型与变形离散元结合的方法以研究连续-非连续耦合系统的破坏演化过程。4.以变形体离散元的摩尔库仑接触模型和分离式裂缝模型为基础,建议了混凝土、岩石等准脆性材料Ⅰ/Ⅱ混合型开裂的拉剪分区开裂准则以及基于缝面法向张开度的刚度强度软化的裂缝扩展准则,提出了分离裂缝模型和变形体离散元的耦合模型并用于分析准脆性材料的受拉开裂和拉剪混合型开裂行为,模型初步实现了系统在外载作用下从小变形到完全破坏的全过程仿真。5.采用本文提出的分离裂缝和变形体离散元的耦合模型分析了Koyna重力坝在动力荷载下的坝体开裂损伤行为,研究坝体在动力荷载下的稳定问题和强震下的大坝破坏模式以及再次经历相同地震时坝体的反应与累计残余变形,初步表明本文模型用于连续-断裂-非连续-破坏全过程的模拟具有可行性。更多还原

【Abstract】 To build a numerical model for simulation of structural progressive collapse from small to large deformation and for numerical modeling of transition process from continua to discontinua is of theoretical and practical significance. Herein, the coupling method of deformable distinct elements with two nonlinear fracture mechanics models-smeared and discrete crack models is presented and applied to analyze the fracture and collapse of high concrete dam. The main contents are summarized as below:1. Based on 3-D rigid distinct element method, a rigid body spring model is developed for simulation of continuum-discontinuum media by achieving the equivalence of the stiffness, strength and external load between the discrete model and the continuous structure. The model is then applied to analyze the failure mechanism of an arch dam with vertical and horizontal construction joints subjected to strong ground motion.2. A rule for selecting the stiffness of discrete interface for deformable distinct element model is presented for simulating the unified model of continuous and discontinuous media. The upward-sliding failure along abutment interface of the Meihua arch dam is simulated by the deformable distinct element method. The results demonstrate that the instability of upward sliding near the dam-abutment interface is the cause of failure, indicating that the corresponding sliding stability analysis in the design of arch dam must be carefully performed when unfavorable weak joints exist and the abutments are relatively flat.3. Based on the blunt crack band theory, systematic formulations of total relationship between stress and strain are deduced for the two nonlinear smeared crack models, i.e. fixed crack model and rotating crack model. The above-mentioned crack models of quasibrittle materials are then inserted in the constitutive models of 3-D deformable distinct element code. Thus, the method based on the coupling damage-crack model with distinct element method is developed to simulate the failure evolution process of continuous and discontinuous system.更多还原