| To meet the enormous energy demands, the development of hydropower sources of energy and other renewable sources have been included12th5-Year Plan in China. It is an important strategic move of energy supplies, energy saving, emission reduction, and protection of the environment many concrete dams have been built, being constructed and will be built in earthquake zone of Southwestern China. A series of tests were performed to investigate nonlinear response, damage mechanism and failure modes of concrete dams, and seismic measure effects under strong earthquake, and the numerical reconstruction of dynamic failure modal test is conducted to study reliability of the results of test. The hydrodynamic pressure model test and the reservoir FEM-based numerical method were applied to study gravity dam-reservoir system interaction, and analysis results of the fluid-solid model were compared with those of the added mass model for reservoir effects on dam body. The main contents in this paper are summarized as follow:(1) The cuboid specimens of5groups were tested to study damage properties, mechanism and modes of emulation concrete. It provides reliable basis for emulation concrete to be better applied to dynamic model rupture test in order to represent the corresponding behavior of its prototype accurately. Since emulation concrete is over brittle, the lab tests were carried out to provide two methods to improve the brittleness of the material. The test results found that emulation concrete mixed with clay or rubber particles can be improved in its brittleness and deformability.(2) The non-full similarity laws are deducted on the basis of the existing similar theory. The disposal skill of fracture characteristics similarity between prototype and model materials is proposed to meet non-full similitude (λε≠1) requirements. The analysis of numerical reconstruction of model test implicates that model test results are reliable when the model is designed according to non-full similarity laws and the treatment skills and the experiment equipment and condition, model material don’t meet all for the similitude requirements.(3) To study the dynamic failure mechanism and seismic measure effects for high concrete gravity dam under strong earthquake, the comparative model experiments on the shaking table were conducted with concrete gravity dam with and without strengthening reinforcement. For the two model dams with and without strengthening reinforcement tested, vulnerable parts of them are the necks near the crests. The results also indicate that the reinforcement is beneficial for improving the seismic-resistant capacity of the gravity dam. To investigate nonlinear responses, stress and damage distributions, the gravity dams with and without strengthening reinforcement under strong earthquake are analyzed with nonlinear numerical model based on concrete plastic damage model and reinforced concrete energy equivalent model. The fluid-solid coupling model is applied to model dam-reservoir interaction in the analysis. It is found that the reinforcing bars can’t improve cracking acceleration of dam, but the cracks opening can be controlled effectively, and the cracks propagations arc restrained in dam surface which is similar with results of dynamic model test. It has a positive impact to maintain integrity of dam.(4) Dynamic model test of gravity dam-reservoir system for gravity dam was carried out on a shaking table. The natural frequency and hydrodynamic pressure on upstream were got from the test. The results of finite element model based on fluid-solid coupling arc well consistent with those of the test, while the Added mass model amplifies the dynamic influence of water on dam. According to the analyses above, finite element method based on fluid-solid coupling should be the first choice to analysis the dam-reservoir interaction. The error analysis was performed by numerical reconstruction of hydrodynamic pressure model test. It is found that water compressibility and its low density is the reason for the error. The feasible methods to reduce the error arc proposed by numerical analysis.(5) Earthquake analysis of gravity dams with five different heights in time domains was performed with the fluid-structure coupling model. The hydrodynamic pressure obtained from the model was compared with Westergaard solutions, and it shows that hydrodynamic pressure can be calculated well with Westergaard formula for the dams with a height of about70m.But when the height of dams is more than160m, it is more reasonable to calculate the dynamic responses of dam-reservoir system with the fluid-structure coupling model. As for the dams with a height of about200m, the influence of foundation on dam-reservoir interaction is significant and must be considered. As for the dams with a height of about70m, the influence of foundation can be neglcctd. Because of many influence factors on hydrodynamic pressure, the Westergaard equation was modified considering the influence of dam height, elasticity, reservoir bottom condition. The results of Westcrgaard formula modified arc coincident with those of fluid-structure coupling models and previous reports. To investigate dynamic responses of gravity dam under dam-water-sediment-foundation interaction system, a2D model was created in which sediment deposition layer is taken as a kind of viscous, compressible and great density fluid and the influence of flexible foundation is also considered. The results obtained from the model are in agreement with those of previous reports:both of flexible foundation and sediment can reduce resonance peaks of dam-reservoir system. In addition, the computational method of the model is simple, and the procedure is finished easily and fast in speed of operation. So it can also be used to study nonlinear dynamic response of dam-reservoir-sediment-foundation systems. |
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