Seismic performance evaluation of roller compacted concrete gravity dams by pseudo dynamic testing

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2016
Aldemir, Alper
The energy demands throughout the world have reached a level that could create irreversible impacts on the environment unless an overall energy policy to reduce the energy production relying on fossil fuels is implemented. The apparent effects of global warming enforced countries to take precautions and to set limits on the fossil fuel consumption. Thus, the renewable energy sources like hydropower, solar energy, biomass, etc. have, nowadays, been encouraged to generate electricity. Certainly, dams are excellent options to generate energy from renewable sources. Yet, they also supply fresh water for dwelling or agricultural usage. Unfortunately, the seismic behavior of dam structures has not been unveiled yet due to the complications stemmed from the interaction of dams with their surrounding media, i.e. flexible foundation and water in reservoir, and due to the complex valley geometries, which requires the consideration of higher mode effects. To solve the complex interaction of dam structures, numerous finite element modeling strategies along with special boundary elements have been proposed in literature. However, the experimental works on dams are constrained with a limited number of shake table experiments. Therefore, in this dissertation, a methodology to adapt pseudo dynamic testing scheme to gravity dam structures is generated. Firstly, the numerical background on the applicability of pseudo dynamic test to distributed mass system is introduced. Then, this methodology is applied to three different specimens consisting of one conventional concrete (CVC) and two roller-compacted concrete (RCC) with different compressive strengths. The prototype specimen was selected as Melen Dam, the highest RCC dam designed in Turkey and the laboratory specimens have a scale factor of 1/75. Each specimen was tested under the effect of three different hazard level earthquakes consecutively. After the completion of earthquake tests, the capacity curve of each specimen was obtained from a pushover experiment. The experiments show that there were no base sliding and stability problems under the effect of each hazard level for none of the specimens. However, the failure of the second specimen (RCC15) was observed during the pushover experiment caused by a body crack reaching the downstream toe of the specimen. Secondly, the numerical ability of current advanced finite element techniques to estimate both the overall demand criteria like base shear, tip displacement, etc. and the crack propagations was investigated. In this part, two different strategies were utilized to model the boundary conditions of the dam specimen. In the first method, the base of the dam specimen was modeled as fixed base and base springs were placed under the foundation block of the dam specimen in the second method. The results reveal that no method was successful enough to predict the correct crack pattern of the dam specimens. However, both methods were convincing for estimating the overall demand parameters. Therefore, it is suggested that the overall demand parameters should be utilized while designing the concrete gravity dams.

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Citation Formats
A. Aldemir, “Seismic performance evaluation of roller compacted concrete gravity dams by pseudo dynamic testing,” Ph.D. - Doctoral Program, Middle East Technical University, 2016.