• Structural Engineering and Mechanics
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• 제57권3호
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• pp.529-541
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• 2016

Under the interaction between dam body, dam foundation and external environment, the dam structural behavior presents the time-varying nonlinear characteristics. According to the prototypical observations, the correct identification on above nonlinear characteristics is very important for dam safety control. It is difficult to implement the description, analysis and diagnosis for dam structural behavior by use of any linear method. Based on the rescaled range analysis approach, the algorithm is proposed to identify and extract the fractal feature on observed dam structural behavior. The displacement behavior of one actual dam is taken as an example. The fractal long-range correlation for observed displacement behavior is analyzed and revealed. The feasibility and validity of the proposed method is verified. It is indicated that the mechanism evidence can be provided for the prediction and diagnosis of dam structural behavior by using the fractal identification method. The proposed approach has a high potential for other similar applications.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.180-187
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• 1998

One of the major difficulties in the seismic analysis of a dam-reservoir system is the treatment of the energy radiation in the upstream direction of the reservoir. In this paper a new transmitting boundary is presented that can model properly the radiation of energy in the far field direction of a semi-infinite reservoir with constant depth. In the newly developed method, effects of surface wave motion are taken into account and the reservoir-foundation interaction is approximately accounted for with an absorbing boundary condition. If a dam has vertical upstream face and the infinitely long reservoir maintains constant depth, then the proposed transmitting boundary can be directly coupled with the model of dam body. In present study, the dam body is assumed to behave elastically and modeled by finite element method. Seismic responses of a dam model are investigated using the newly developed transmitting boundary.

• Structural Engineering and Mechanics
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• 제33권4호
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• pp.407-428
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• 2009

The effects of the uniform and spatially varying ground motions on the stochastic response of fluid-structure interaction system during an earthquake are investigated by using the displacement based fluid finite elements in this paper. For this purpose, variable-number-nodes two-dimensional fluid finite elements based on the Lagrangian approach is programmed in FORTRAN language and incorporated into a general-purpose computer program SVEM, which is used for stochastic dynamic analysis of solid systems under spatially varying earthquake ground motion. The spatially varying earthquake ground motion model includes wave-passage, incoherence and site-response effects. The effect of the wave-passage is considered by using various wave velocities. The incoherence effect is examined by considering the Harichandran-Vanmarcke and Luco-Wong coherency models. Homogeneous medium and firm soil types are selected for considering the site-response effect where the foundation supports are constructed. A concrete gravity dam is selected for numerical example. The S16E component recorded at Pacoima dam during the San Fernando Earthquake in 1971 is used as a ground motion. Three different analysis cases are considered for spatially varying ground motion. Displacements, stresses and hydrodynamic pressures occurring on the upstream face of the dam are calculated for each case and compare with those of uniform ground motion. It is concluded that spatially varying earthquake ground motions have important effects on the stochastic response of fluid-structure interaction systems.

• Advances in concrete construction
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• 제6권3호
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• pp.269-283
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• 2018

This study presents the effects of geometrical dimensions of concrete gravity dams on the seismic response considering different base width/dam height (L/H) ratios. In the study, a concrete gravity dam with the height of 200 m is selected and finite element models of the dam are constituted including five different L/H ratios such as 0.25, 0.5, 0.75, 1.00, 1.25. All dams are modeled in ANSYS software considering dam-reservoir-foundation interaction. 1989 Loma Prieta earthquake records are applied to models in upstream-downstream direction and linear time history analyses are performed. Dynamic equilibrium equations of motions obtained from the finite element models of the coupled systems are solved by using Newmark time integration algorithm. The seismic response of the models is evaluated from analyses presenting natural frequencies, mode shapes, displacements and principal stresses. The results show that the L/H ratios considerably affect the seismic response of gravity dams. Also, the model where L/H ratio is 1.00 has more desirable results and most appropriate representation of the seismic response of gravity dams.

• Structural Engineering and Mechanics
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• 제72권2호
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• pp.141-153
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• 2019

The effect of galleries on the earthquake behavior of dams should be investigated to obtain more realistic results. Therefore, a roller compacted concrete (RCC) dam with and without galleries are examined under ground motion effects. For this purpose, Cine RCC dam constructed in Aydın, Turkey, is selected in applications. The optimal mesh around galleries is investigated to obtain the most realistic results. Two-dimensional finite element models of Cine RCC dam with and without galleries are prepared by using ANSYS software. Empty and full reservoir conditions were taken into account in the time-history analyses. Hydrodynamic effect of the reservoir water was taken into account considering two-dimensional fluid finite elements based on the Lagrangian approach. It is examined that how principle stresses and displacements change by height and during earthquake. The dam-foundation-reservoir interaction was taken into consideration with contact-target element pairs. The displacements and principle stress components obtained from the linear analyses are compared each other for various cases of reservoir water and galleries. According to numerical analyses, the effect of galleries is clear on the response of RCC dam. Besides, hydrodynamic water effect obviously increases the principle stress components and horizontal displacements of the dam.

• 한국지진공학회논문집
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• 제3권1호
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• pp.123-132
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• 1999

댐-호소 계의 지진응답해석에 있어서의 어려운 문제 중 하나는 댐 상류방향으로의 에너지 방사를 적절하게 처리하는 것이다 본 논문에서는 깊이가 일정한 호소 원역으로의 에너지 방사를 잘 모델링할 수 있는 전달경계를 제시하였다 개발된 방법에서 수면파의 영향을 고려하였으며 호소-지반의 상호작용을 근사적으로 표현할수 있는 흡수경계조건도 도입하였다 댐과 호소의 경계면이 지표면에 수직하고 호소의 깊이가 일정할 경우에는 제안된 전달경계를 댐체의 모델에 직접 연결할 수 있다 댐체는 선형탄성거동을 가정하여 유한요소로 모델링 하였다 얻어진 댐-호소 계의 운동방정식을 이용하여 댐의 지진응답특성을 조사하였다

• Advances in concrete construction
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• 제9권5호
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• pp.503-510
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• 2020

Concrete dams are important structures due to retaining amount of water on their reservoir. So such kind of structures have to be designed against static and dynamic loads. Especially considering on critical importance against blasting threats and environmental safety, dams have to be examined according to the blast loads. This paper aims to investigate structural response of concrete gravity dams under blast loads. For the purpose Sarıyar Concrete Gravity Dam in Turkey is selected for numerical application with its 85 m of reservoir height (H), 255 m of reservoir length (3H), 72 m of bottom and 7 m of top widths. In the study, firstly 3D finite element model of the dam is constituted using ANSYS Workbench software considering dam-reservoir-foundation interaction and a hydrostatic analysis is performed without blast loads. Then, nearly 13 tons TNT explosive are considered 20 m away from downstream of the dam and this is modeled using ANSYS AUTODYN software. After that explicit analyses are performed through 40 milliseconds. Lastly peak pressures obtained from analyses are compared to empirical equations in the literature and UFC 3-340-02 standard which provide unified facilities criteria for structures to resist the effects of accidental explosions. Also analyses' results such as displacements, stresses and strains obtained from both hydrostatic and blasting analysis models are compared to each other. It is highlighted from the study that blasting analysis model has more effective than the only hydrostatic analysis model. So it is highlighted from the study that the design of dams should be included the blast loads.

• Advances in Computational Design
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• 제3권1호
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• pp.87-112
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• 2018

In this study, it is aimed to present engineering software to estimate the structural response of concrete arch dam. Type-1 concrete arch dam constructed in the laboratory is selected as a reference model. Finite element analyses and experimental measurements are conducted to show the accuracy of initial model. Dynamic analyses are carried out by spectrum analysis under empty reservoir case considering soil-structure interaction and fixed foundation condition. The displacements, principal stresses and strains are presented as an analysis results at all nodal points on downstream and upstream faces of dam body. It is seen from the analyses that there is not any specific ratio between prototype and scaled models for each nodal point with different scale values. So, dynamic analyses results cannot be generalized with a single formula. To eliminate this complexity, the regression analysis, which is a statistical method to obtain the real model results according to the prototype model by using fitting curves, is used. The regression analysis results are validated by numerical solutions using ANSYS software and the error percentages are examined. It is seen that 10% error rates are not exceeded.

• Computers and Concrete
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• 제22권1호
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• pp.101-116
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• 2018

As one of the most important engineering structures, arch dams are huge constructions built with human hands and have strategical importance. Because of the fact that long construction duration, water supply, financial reasons, major loss of life and material since failure etc., the design of arch dams is very important problem and should be done by expert engineers to determine the structural behavior more accurately. Finite element analyses and non-destructive experimental measurements can be used to investigate the structural response, but there are some difficulties such as spending a long time while modelling, analysis and in-situ testing. Therefore, it is more useful to conduct the research on the laboratory conditions and to transform the obtained results into real constructions. Within the scope of this study, it is aimed to determine the structural behavior of arch dams considering experimentally validated prototype laboratory model using similitude and scaling laws. Type-1 arch dam, which is one of five arch dam types suggested at the "Arch Dams" Symposium in England in 1968 is selected as reference prototype model. The dam is built considering dam-reservoir-foundation interaction and ambient vibration tests are performed to validate the finite element results such as dynamic characteristics, displacements, principal stresses and strains. These results are considered as reference parameters and used to determine the real arch dam response with different scales factors such as 335, 400, 416.67 and 450. These values are selected by considering previously examined dam projects. Arch heights are calculated as 201 m, 240 m, 250 m and 270 m, respectively. The structural response is investigated between the model and prototype by using similarity requirements, field equations, scaling laws etc. To validate these results, finite element models are enlarged in the same scales and analyses are repeated to obtain the dynamic characteristics, displacements, principal stresses and strains. At the end of the study, it is seen that there is a good agreement between all results obtained by similarity requirements with scaling laws and enlarged finite element models.

• Structural Engineering and Mechanics
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• 제48권6호
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• pp.775-789
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• 2013

The current paper proposes a boundary element formulation, applicable to 2-D and 3-D elastostatics problems using a unified approach for transformations of the domain integrals into boundary integrals. The method is applicable to linear problems encompassing both finite and infinite multi-region domains allowing non-vanishing body forces. Numerical results agree quite well with the analytical solutions; while the present method offers easy formulation with less numerical efforts in comparison to FEM or some BEM which need interior points to treat arbitrary body forces. It is demonstrated that the method has the potential to have profound impact on engineering design, notably in dam-foundation interaction.