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A New Modal Technique for Seismic Analysis of Arch Dams Including Dam-Reservoir Interaction
Concrete arch dams, specially the large ones, are important structures which could be considered as critical points in each region. They have extremely large damage potentials and they must also be able to endure the effects of natural hazards. On the other hand, the earthquake is the main natural hazard which impacts the dam body. During the earthquake, huge amounts of forces imposed on the dam create large stresses in the various zones of the dam body. This may cause significant impacts or even dangerous damages. The above mentioned forces include the inertial forces of the dam body as a vibrating structure and additional forces which are due to the dam-reservoir-foundation rock interactions. These complicated effects influence the seismic responses of concrete arch dams significantly. Therefore, they should be considered in the dynamic analysis procedures of the dams. In this article, a new effective procedure is implemented for evaluating the seismic response of concrete arch dams including dam-reservoir interaction effects in the frequency domain. It is worthwhile to mention that the modeling concept is based on the FE-(FE-HE) approach. This means, the dam is discretized by solid finite elements, while, the reservoir is divided into two parts, a near field region (usually an irregular shape) in the vicinity of the dam and a far field part (assuming uniform channel), which extends to infinity. The former region is discretized by fluid finite elements and the latter part is modeled by a three-dimensional fluid hyper-element. To achieve a suitable efficiency, the analysis is carried out by the general modal analysis. For this reason, a new technique is proposed for calculating an approximation for the coupled mode shapes of fluid-structure systems. This can be visualized as a modification for the original Sandberg method (Sandberg, 1995). Moreover, a simple relation is derived which enables one to readily calculate the left eigen-vector from the corresponding right eigen-vector. Overall, this new approximate approach is believed to be very promising and it is shown that it could lead to almost exact eigen-values and coupled modes of the dam-reservoir systems. Also, the analysis of the Morrow Point arch dam is presented as a numerical example and the frequency response functions are provided for different cases.
A New Modal Technique for Seismic Analysis of Arch Dams Including Dam-Reservoir Interaction
Concrete arch dams, specially the large ones, are important structures which could be considered as critical points in each region. They have extremely large damage potentials and they must also be able to endure the effects of natural hazards. On the other hand, the earthquake is the main natural hazard which impacts the dam body. During the earthquake, huge amounts of forces imposed on the dam create large stresses in the various zones of the dam body. This may cause significant impacts or even dangerous damages. The above mentioned forces include the inertial forces of the dam body as a vibrating structure and additional forces which are due to the dam-reservoir-foundation rock interactions. These complicated effects influence the seismic responses of concrete arch dams significantly. Therefore, they should be considered in the dynamic analysis procedures of the dams. In this article, a new effective procedure is implemented for evaluating the seismic response of concrete arch dams including dam-reservoir interaction effects in the frequency domain. It is worthwhile to mention that the modeling concept is based on the FE-(FE-HE) approach. This means, the dam is discretized by solid finite elements, while, the reservoir is divided into two parts, a near field region (usually an irregular shape) in the vicinity of the dam and a far field part (assuming uniform channel), which extends to infinity. The former region is discretized by fluid finite elements and the latter part is modeled by a three-dimensional fluid hyper-element. To achieve a suitable efficiency, the analysis is carried out by the general modal analysis. For this reason, a new technique is proposed for calculating an approximation for the coupled mode shapes of fluid-structure systems. This can be visualized as a modification for the original Sandberg method (Sandberg, 1995). Moreover, a simple relation is derived which enables one to readily calculate the left eigen-vector from the corresponding right eigen-vector. Overall, this new approximate approach is believed to be very promising and it is shown that it could lead to almost exact eigen-values and coupled modes of the dam-reservoir systems. Also, the analysis of the Morrow Point arch dam is presented as a numerical example and the frequency response functions are provided for different cases.
A New Modal Technique for Seismic Analysis of Arch Dams Including Dam-Reservoir Interaction
Sani, Ahmad Aftabi (author) / Lotfi, Vahid (author)
Technical Council on Lifeline Earthquake Engineering Conference (TCLEE) 2009 ; 2009 ; Oakland, California, United States
TCLEE 2009 ; 1-12
2009-06-24
Conference paper
Electronic Resource
English
A New Model Technique for Seismic Analysis of Arch Dams Including Dam-Reservoir Interaction
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