• 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

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.874-882
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• 2009

Continuous monitoring of dam performance is essential to earth and rockfill dams safety because it has to be guaranteed for safety during construction period of course and from initial impounding to a long term maintenance period of dam. Among the 31 dams managed by Kwater at present, the proportion of dams being over 20 years after completion of construction is 42% and it is estimated that the loss rate of monitoring devices will be increase as times. Monitoring devices would be impossible to repair since those are mostly installed in the dam body and foundation. If repairing of monitoring devices is possible, the expenditure will be expensive. Therefore reasonable decision making for abandonment, repair and alternation for loss of monitoring devices would be needed through the establishment of key instrument for earth and rockfill dam safety. In this study the process of monitoring for safety were modeled by failure modes of dams, adverse conditions related to failure mode, indicators of adverse condition and monitoring devices The relationship between failure mode and monitoring devices were systematically analyzed and established and evaluation technique for qualifying the importance of monitoring devices were presented.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1999년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.267-274
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• 1999

Since the seismic response of dams can be strongly influenced by the dam-reservior interaction in needs to be taken into account in the seismic design of dams. In general a substructure method is employed to solve the dam-reservoir interaction problem in which the dam body is modeled with finite elements and the infinite region of a reservoir using a transmitting boundary. When the water is modeled as a compressible fluid the equation is formulated in frequency domain. But nonlinear behavior of dam body cannot be studied easily in the frequency domain method. In this study time domain formulation of the dam-reservoir-soil interaction is proposed based onthe lumped parameter modeling of the reservoir region, The frequency dependent dynamic-stiffness coefficients of the reservoir are converted into frequency independent lumped-parameters such as masses dampers and springs. The soil-structure interactionis modeled using lumped parameters in similar way. the ground is assumed as a visco-elastic stratum on the rigid bedrock. The dynamic stiffnesses of the rigid surface foundation are calculated using the hyperelement method and are converted into lumped parameters. The application example demonstrated that the lumped parameter model gives almost identical results with the frequency domain formulation.

• Computers and Concrete
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• 제10권3호
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• pp.277-294
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• 2012

The aim of the study is to determine the modal parameters of a prototype damaged arch dam by operational modal analysis (OMA) method for some damage scenarios. For this purpose, a prototype arch dam-reservoir-foundation model is constructed under laboratory conditions. Ambient vibration tests on the arch dam model are performed to identify the modal parameters such as natural frequency, mode shape and damping ratio. The tests are conducted for four test-case scenarios: an undamaged dam with empty reservoir, two different damaged dams with empty reservoirs, and a damaged dam with full reservoir. Loading simulating random impact effects is applied on the dam to crack. Cracks and fractures occurred at the middle of the upper part of the dams and distributed through the abutments. Sensitivity accelerometers are placed on the dams' crests to collect signals for measurements. Operational modal analysis software processes the signals collected from the ambient vibration tests, and enhanced frequency domain decomposition and stochastic subspace identification techniques are used to estimate modal parameters of the dams. The modal parameters are obtained to establish a basis for comparison of the results of two techniques for each damage case. Results show that approximately 35-40% difference exists between the natural frequencies obtained from Case 1 and Case 4. The natural frequencies of the dam considerably decrease with increasing cracks. However, observation shows that the filled reservoir slightly affected modal parameters of the dam after severe cracking. The mode shapes obtained are symmetrical and anti-symmetrical. Apparently, mode shapes in Case 1 represent the probable responses of arch dams more accurately. Also, damping ratio show an increase when cracking increases.

• Structural Monitoring and Maintenance
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• 제4권1호
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• pp.17-31
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• 2017

Since extensometers are used to determine the absolute deformation of foundation and abutments and all results are obtained in reference to the base rod, the accuracy of these results has been constantly a subject of debate. In this regard, locating and installing extensometers outside the range of effect zone is also another challenge. The main purpose of this paper is to investigate and modify extensometers results based on the mentioned issues. For this aim, the concrete RCC Zhaveh dam in Iran was selected as the case study. To study the results of extensometers installed in this dam, first, the 3DEC_DP 5.00 software was applied for numerical modeling. Parameters such as discontinuities, dead load and piezometric pressure in the interface of concrete and rock were considered. Next, using the results obtained from 6 extensometers in foundation and abutments and 4 clinometers in dam body, the numerical model was calibrated through back analysis method. The results indicate that the base rod is moved and is not recommended being used as the base point. In other words, because installation of base anchor outside the range of effect zone is not possible due to the operational and economic considerations, the obtained results are not accurate enough. The results indicate a considerable 2-3 mm displacement of the base rod (location of the base anchor) in reference to the real zero point location, which must be added to the base rod results.

• 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.

• 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.

• 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.

• 한국지반환경공학회 논문집
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• 제23권2호
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• pp.25-36
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• 2022

본 연구에서는 감압정의 침투수 처리 효과를 정량적으로 분석하여 소규모 필댐과 하천제방에서 제체를 통과하는 침투수의 처리 효과를 확인하였다. 이를 위해 댐과 제방에서의 제체와 기초지반의 투수 특성에 따른 침투해석을 수행하여 침투수의 거동특성을 파악하여 댐 제체 선단에 작용하는 양압력을 분석하였다. 또한 감압정의 설치 조건을 변수로 분석하여 댐 또는 제방의 제체 선단에 작용하는 양압력의 감소 효과를 분석함으로써 침투수 처리 효과를 분석하였다. 감압정은 파이핑 현상 또는 양압력을 유발하는 제체의 선단 하부 기초지반에서의 작용 간극수압을 감소시키는 효과가 있는 것으로 평가되었으며, 제체의 높이 및 비탈면 기울기와 같은 기하학적 조건에 크게 영향을 받지 않고 간극수압을 관리할 수 있는 것으로 확인되었다. 투수성이 상대적으로 큰 조립토 지반에 비해 세립토 지반에서 감압정의 간극수압 저감 효과는 상대적으로 저하되지만 감압정이 설치되지 않은 조건에 비해서 간극수압 저감 효과를 기대할 수 있는 것으로 확인되었다. 감압정의 직경, 설치 깊이에 따라서 감압정의 저감 효과는 상대적으로 차이가 발생하지만 감압정의 설치 깊이가 침투수 관리에 가장 효과적인 것으로 확인되었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.119-126
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• 2002

Fractures, especially faults have most significant influence on the difficulties encountered in various engineering and mining works, because they can give rise to inevitable reductions in shear strength as well as large increase in permeability. Thus, before underground access is possible, it is desirable to estimate the distribution and geometry of fractures in advance, if reliable structural data from e.g. Televiewer tool are available. To this end, fracture face mapping is just the evaluation method used to form a fracture image determined by intersecting of each fracture plane with a selected plane section of a rock mass, assuming that all fractures be planar with fixed-aperture. Although many fractures are geometrically complex and others are altered chemically, according to the abundant experiments in recent years, it would seem that the technique could be applied to benefit the design of numerous engineering works such as slope stability, tunnel excavations, dam foundation and diverse environmental works. This paper presents at first an evaluation algorithm for fracture face mapping and then concludes with various representative examples of applications.