Concrete Gravity Dams Reliability Analysis Based On Response Surface Approach

At present, the gravity dam's safety evaluation is based on the forecasting of dam safetyfactor which is a constant value. Since the safety factor can't consider the existent variabilityof water level, elastic modulus and strength of materials, etc., it is difficult to reflect the realstate reasonably. The probability statistic method, which could take all the variability of thematerials into account and solve the reliability index of the dam strictly, could reflect thesafety degree preferable.To calculate the reliability index, a definite performance function is needed. But, for thecomplexity of gravity dam system and the highly nonlinear characteristics of the responsefunction, explic equation is hard to obtain, which make the reliability index difficult to obtain.This paper fitting the gravity dam performance function with RSA (Response SurfaceApproch) which can simulate the function accurately within several certainly test. Thevalidity of the RSM is verified in this paper.This paper discuss about the failure road and failure mode of gravity dam system. Threefailure mode, strength safety, anti-sliding stability and hositing safety of working gate,divided by ultimate capacity state & ultimate service state, are putting forward. The impact ofevery failure road on different failure modes should be considered. Some basic issues in theaseismic reliability analysis, like the calculation of aseismic reliability, estimation method ofthe earthquake occurrence probability and the reliability index after the dam suffered anearthquake etc, are discussed in this paper. Then, the course of aseismic reliability analsys isSimplified.The aseismic reliability index in the design reference period can be obtainedapproximately by just calculating the reliability index of the dam that under any seismicintensity. This idea is clear and easy to put in practice. An improved pseudo-static method isadopted to calculate the response under an earthquake. To verify the method presented in thispaper, Longkaikou gravity dam, on Jinsha river, has been used as an example. Based on theprogram of reliability index calculation that developed by the writer, system reliability of the24th dam under both static and dynamic case is calculated and contrasted.At last, the advanced research orientation of gravity dam system reliability is discussed.