Performance-based Seismic Fragility Analysis And Risk Evaluation Of Concrete Gravity Dam

The group of large size hydraulic, such as Jinping First-casecade(305m),Guandi(168m), Lianghekou(293m), Longkaikou(167m) and Longtan(196.5m) HydroStations, is being developing or will be developed in the southwest where theearthquake intensity is high. With the high dams constructed, the risk that associatedby dam manage under earthquake will be rise substantially. So the seismic safetyevaluation for dam becomes a very important problem. As Gravity dams are widelyadopted in high dams, construction, the research about risk evaluation and fragilityanalysis for these dams is of important significance. Some recent studies showed thatstrength safety factor doesn’t mean structure safety. And performance-based seismicdesign method has been proposed. The core in the theory is multi-performance levelsseismic design, with the objective that is not only protecting human life but alsomaking seismic designs economical. The principles and methods of this theory havegiven us great ways and views to study the risk and seismic fragility of concretegravity dam. The main work content as follows：(1) Nonlinear seismic analysis of a concrete gravity dam was performed based onthe plastic damage theory. Based on the seismic safety of structural performance, aseismic damage assessment model considering the influence of the damage of theupper part, the crack length and the damage of curtain grouting on dam safety wasdeveloped for describing the damage of the concrete gravity dam. And dynamiccontact theory is applied to simulate the sliding of weak-lubricant layer. The stabilityof the dam base is evaluated from the distribution of the yield zone that appeared inthe shallow foundation, the integrity of grout curtain and the performance of drainageholes. On the basis of the above-mentioned research, a seismic damage assessmentmodel is developed for describing the damage of the concrete gravity dam system. Itholds that the seismic behavior of the system is determined by the worst damagemodel when it is hit by a destructive earthquake.(2) In fragility analysis the uncertainty due to stochastic simulation and theinfluence of the uncertainty of the parameters in the model are taken into account. Byuse of the Latin Hypercube Sampling, a set of sample was generated. And by meansof the above seismic damage assessment method, the seismic fragility curves for concrete gravity dams are established.(3) Based on digital elevation model, data organization method andThree-Dimensional visualization technology of GIS, the digital drainage area thatsimulates the flood routing is constructed. And then, build loss evaluation model ofvarious damage states of concrete gravity dam under earthquake by using vector datamodel and raster data model.(4) The exceeding probability of seismic intensity is got by seismic hazardanalysis. By combining seismic hazard analysis, fragility analysis and loss assessmentof concrete gravity dams, seismic risk is evaluated and the probability of socialdisaster caused by dam under earthquakes is got.