Performance-Based Seismic Damage Analysis And Risk Evaluation Model For Concrete Dam-Foundation System

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.