【作者】 沈怀至；

【导师】 张楚汉；

【作者基本信息】 清华大学 ， 水利工程， 2007， 博士

【摘要】 本文在研究基于性能的坝体、坝基交界面不同破损等级的评价准则、大坝易损性分析与风险评价方法基础上,初步建立了基于性能的大坝-地基系统在不同概率水平地震作用下的抗震设计分析理论框架,并应用于基于性能的混凝土高坝的安全评价与风险优化决策中,主要研究内容包括:1.在基于性能的砼坝抗震简化模型方面,建立了一种重力坝地震破损分析拟静力的简化方法。在基于第一振型等效地震荷载(施加方向分别指向上游或下游)基础上,应用弥散裂缝模型,建立了非线性拟静力简化方法,得到了单调加载极限变形,作为基于性能的混凝土坝破损分析的初步工具。2.在基于性能的砼坝抗震动力模型方面,根据大坝动力线弹性与非线性损伤断裂模型得到的地震应力水平、超应力累积持时与典型开裂特征,建立了一种基于大坝损伤开裂的地震破损评价模型,并建议了相应的损伤评价指标DM(Damage Measure)。3.在基于性能的坝基交界面抗震分析方面,根据岩体结构面的法向和切向本构关系,分别引入坝体底面刚性接触和弹性接触假设,建立了坝基交界面非线性接触模型,提出了以坝基交界面屈服范围、残余滑动位移以及坝基动力抗滑稳定安全系数等为评价指标的坝基交界面地震破损安全评价方法。4.在应用以上2、3所述模型的基础上,引入坝体-地基系统破损概率即易损性理念,通过拉丁抽样得到的坝体与地基材料参数抽样样本组合和对数正态分布假设,提出了大坝易损性分析方法,给出了考虑坝体破损、坝基交界面的屈服与残余滑动位移的地震易损性概率曲线,并提出了坝体-坝基系统整体易损性分析方法。5.在工程应用方面,采用本文上述提出的抗震破损模型,应用于金安桥重力坝坝体-地基系统的地震易损性分析,结合大坝设计地震超越概率,建立了大坝抗震风险分析模型以及考虑投资-效益准则与目标性能约束的抗震优化决策方法。根据坝体配筋加固方案,计算出采用抗震措施前后的风险概率及其经济损失评价,将基于性能的抗震风险模型运用于混凝土重力坝的抗震风险评价中。更多还原

【Abstract】 It is of theoretical and practical significance to build a theoretical framework for performance-based seismic design of concrete dams at different levels of earthquake. A method of performance-based seismic analysis for concrete dams is presented including seismic evaluation model for analysis of damage and cracking behavior of dam, sliding behavior at the interface between dam and foundation, and a model of economic risk optimization with seismic fragility analysis. As an engineering application, it is then applied to study the performance-based safety assessment and decision-making with optimization of the Jinanqiao gravity dam.The main contents are summarized as follows:1. A simple pseudo-static method of damage and cracking for gravity dams is developed for performance-based seismic design and analysis of concrete dams. Based on the smear crack model and equivalent static loadings (acting towards upstream and downstream, respectively) considering fundamental mode of the dam, ultimate deformations of the gravity dam under monotonic equivalent loadings in seismic damage model can be obtained. As a preliminary tool, the model can be used in performance-based seismic damage analysis of concrete dam for simplification2. The seismic stress level, cumulative duration of overstress by using linear dynamic analysis can be obtained for failure zones of the dam under different levels of earthquake. Further, by using nonlinear plastic-damage analysis, a seismic damage model and corresponding damage measure (DM) index criterion are established.3. Based on normal and tangential constitutive relationships of dam-foundation contact surface, a nonlinear contact model along interface is developed by assuming rigid and elastic contact at the surface in the performance-based analysis of dam- foundation interface. Criterion of safety evaluation for the dam-foundation interface including the ratio of yielding identification region, maximum relative and residual sliding displacements, and dynamic safety factor against sliding, etc. is proposed. 4. Based on above-mentioned 2nd and 3rd items, a damage probability concept of dam-foundation system, namely fragility of the system, is introduced. A numerical analysis model for computation of the seismic fragility of dam is developed by selecting sample sets of material variables using Latin hypercube method and assuming lognormal distribution. Fragility curves of different damage degrees for dam monolith and the interface along dam-foundation are respectively presented. Also, the fragility analysis of entire dam-foundation system is proposed.5. As an engineering application of the method, risk analysis and seismic optimum decision-making considering investment-benefit criterion and performance restriction conditions are founded associated with seismic hazard analysis in the region. The method is then applied to the performance-based seismic design of Jinanqiao concrete gravity dam. Risk probabilities and economic losses are compared between reinforcements strengthening and without reinforcements strengthening in the dam monolith, and alternative is given.更多还原