• Computers and Concrete
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• 제27권2호
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• pp.143-152
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• 2021

Large dams are a part of the infrastructure of any society, and a huge amount of resources are consumed to build them. Among the various types of dams, the optimum design of concrete gravity dams requires special attention because these types of dams require a huge amount of concrete for their construction. On the other hand, concrete gravity dams are among the structures whose design, regarding the acting forces, geometric parameters, and resistance and stability criteria, has some complexities. In the present study, an optimization methodology is proposed based on Sequential Quadratic Programming (SQP), and a computer program is developed to perform optimization of concrete gravity dams. The optimum results for 45 concrete gravity dams are studied and regression analyses are performed to obtain some explicit formulas for optimization of the gravity dams. The optimization of concrete gravity dams can be provided easily using the developed formulas, without the need to perform any more optimization process.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.183-188
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• 2001

The objective of this study is firstly to frame up the seismic safety of concrete gravity dams. It is necessary to analyze seismic response and evaluate seismic performance of concrete gravity dams during earthquake. In this study, seismic damage and dynamic analysis of concrete gravity dams using SAP2000 program are peformed. Additional dynamic water pressure due to earthquake was considered as additional mass for numerical seismic analysis. But, further research will be necessary for the seismic stability of dams.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.325-330
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• 2000

The objective of this study is firstly to frame up the seismic safety of concrete gravity dams. It is necessary to analyze seismic response and evaluate seismic performance of concrete gravity dams during earthquake. In this study, seismic damage and dynamic analysis of concrete gravity dams using SAP2000 program are performed. Additional dynamic water pressure due to earthquake considered as additional mass for numerical seismic analysis. But, further research will be needed for the seismic stability of dams.

• 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.

• 한국안전학회지
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• 제31권4호
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• pp.64-74
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• 2016

Recently, the seismic stability evaluation of concrete gravity dams is raised due to the failure of dams occurred by the Izmit, Turkey and JiJi, Taiwan earthquake in 1999. Dams failure may incur loss of life and properties around the dam as well as damage to dam structure itself. Recently, there has been growing much concerns about "earthquake - resistance" or "seismic safety" of existing concrete gravity dams designed before current seismic design provisions were implemented. This research develops three evaluation levels for seismic stability of concrete gravity dams on the basis of the evaluation method of seismic stability of concrete gravity dams in U.S.A., Japan, Canada, and etc. Level 1 is a preliminary evaluation which is for purpose of screening. Level 2 is a pseudo-static evaluation on the basis of the seismic intensity method. And level 3 is a detail evaluation by the dynamic analysis. Evaluation results on existing concrete gravity dams on operation showed good seismic performance under designed artificial earthquake(KHC earthquake).

• Earthquakes and Structures
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• 제18권3호
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• pp.285-296
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• 2020

Dams are important structures for management of water supply for irrigation or drinking, flood control, and electricity generation. In seismic regions, the structural safety of concrete gravity dams is important due to the high potential of life and economic loss if they fail. Therefore, the seismic analysis of existing dams in seismically active regions is crucial for predicting responses of dams to ground motions. In this paper, earthquake response of concrete gravity dams is investigated using the finite element (FE) method. The FE model accounts for dam-water-foundation rock interaction by considering compressible water, flexible foundation effects, and absorptive reservoir bottom materials. Several uncertainties regarding structural attributes of the dam and external actions are considered to obtain the fragility curves of the dam-water-foundation rock system. The structural uncertainties are sampled using the Latin Hypercube Sampling method. The Pine Flat Dam in the Central Valley of Fresno County, California, is selected to demonstrate the methodology for several limit states. The fragility curves for base sliding, and excessive deformation limit states are obtained by performing non-linear time history analyses. Tensile cracking including the complex state of stress that occurs in dams was also considered. Normal, Log-Normal and Weibull distribution types are considered as possible fits for fragility curves. It was found that the effect of the minimum principal stress on tensile strength is insignificant. It is also found that the probability of failure of tensile cracking is higher than that for base sliding of the dam. Furthermore, the loss of reservoir control is unlikely for a moderate earthquake.

• Computers and Concrete
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• 제13권2호
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• pp.209-220
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• 2014

Vibration based damage detection is very popular in the civil engineering area. Especially, special structures like dams, long-span bridges and high-rise buildings, need continues monitoring in terms of mechanical properties of material, static and dynamic behavior. It has been stated in the International Commission on Large Dams that more than half of the large concrete dams were constructed more than 50 years ago and the old dams have subjected to repeating loads such as earthquake, overflow, blast, etc.,. So, some unexpected failures may occur and catastrophic damages may be taken place because of theloss of strength, stiffness and other physical properties of concrete. Therefore, these dams need repairs provided with global damage evaluation in order to preserve structural integrity. The paper aims to show the effectiveness of the model updating method for global damage detection on a laboratory arch dam model. Ambient vibration test is used in order to determine the experimental dynamic characteristics. The initial finite element model is updated according to the experimentally determined natural frequencies and mode shapes. The web thickness is selected as updating parameter in the damage evaluation. It is observed from the study that the damage case is revealed with high accuracy and a good match is attained between the estimated and the real damage cases by model updating method.

• 한국산림과학회지
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• 제111권2호
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• pp.276-286
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• 2022

이 연구는 「사방시설의 유지관리 지침」에 의거하여 수행된 노후 콘크리트사방댐에 대한 정밀점검 결과를 분석하여, 향후 콘크리트사방댐의 관리 방안을 수립하는데 필요한 기초자료를 제공하기 위하여 수행되었다. 이를 위하여 경상북도 사유림에 위치한 준공 후 20년 이상 경과된 54개 콘크리트 사방댐에 대한 정밀점검의 결과를 통계적 방법으로 분석하였다. 외관 결함사항 점검의 결과, 보수 혹은 후속조치가 필요한 것이 18개소(33.4%)를 차지하였으며, 조사자 보정점수로 인하여 종합등급이 변경된 사례로 15개소가 나타나 관련 기준과 지표의 표준화가 필요할 것으로 생각되었다. 콘크리트 압축강도시험의 결과, 기준치에 미달하는 것은 19개소(35.2%)로 조사되었으며, 이중에는 외관 결함사항 점검 결과 상태가 양호한 것으로 판단된 A등급에서도 8개소가 포함되어 있었다. 또한, 종합점수와 콘크리트 압축강도 사이에는 뚜렷한 상관관계가 나타나지 않았으나, 종합등급별로 콘크리트 압축강도는 통계적으로 유의한 차이가 있었다. 한편, 준공 후 경과연수에 따른 사방댐의 특성 변화를 분석한 결과, 시간 경과와 종합점수 및 압축강도의 변화는 특별한 경향을 나타내지 않았다. 하지만, 보수·후속조치가 필요한 사방댐과 압축강도 기준치 미달 사방댐의 누적 비율은 모두 시간 경과와 강한 양의 선형관계가 있는 것으로 분석되어, 이를 활용하면 콘크리트사방댐의 노후 특성을 파악할 수 있을 것으로 기대되었다.

• Structural Engineering and Mechanics
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• 제21권4호
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• pp.423-435
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• 2005

A modal approach is proposed for dynamic analysis of concrete arch dam-reservoir systems in frequency domain. The technique relies on mode shapes extracted by considering the symmetric parts of total mass and stiffness matrices. Based on this method, a previously developed program is modified, and the response of Morrow Point arch dam is studied for various conditions. The method is proved to be very effective and it is an extremely convenient modal technique for dynamic analysis of concrete arch dams.

• Computers and Concrete
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• 제1권3호
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• pp.285-302
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• 2004

A FE-(FE-HE)-BE procedure is presented for dynamic analysis of concrete arch dams. In this technique, dam body is discretized by solid finite elements, while the reservoir domain is considered by a combination of fluid finite elements and a three-dimensional fluid hyper-element. Furthermore, foundation rock domain is handled by three-dimensional boundary element formulation. Based on this method, a previously developed program is modified, and the response of Morrow Point arch dam is studied for various conditions. Moreover, the effects of canyon shape on response of dam, is also discussed.