• International Journal of Concrete Structures and Materials
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• 제10권3호
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• pp.307-323
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• 2016

The nonlinear behaviors of recycled aggregate concrete (RAC) frame structure are investigated by numerical simulation method with 3-D finite fiber elements. The dynamic characteristics and the seismic performance of the RAC frame structure are analyzed and validated with the shaking table test results. Specifically, the natural frequency and the typical responses (e.g., storey deformation, capacity curve, etc.) from Model 1 (exclusion of strain rate effect) and Model 2 (inclusion of strain rate effect) are analyzed and compared. It is revealed that Model 2 is more likely to provide a better match between the numerical simulation and the shaking table test as key attributes of seismic behaviors of the frame structure are captured by this model. For the purpose to examine how seismic behaviors of the RAC frame structure vary under different strain rates in a real seismic situation, a numerical simulation is performed by varying the strain rate. The storey displacement response and the base shear for the RAC frame structure under different strain rates are investigated and analyzed. It is implied that the structural behavior of the RAC frame structure is significantly influenced by the strain rate effect. On one hand, the storey displacements vary slightly in the trend of decreasing with the increasing strain rate. On the other hand, the base shear of the RAC frame structure under dynamic loading conditions increases with gradually increasing amplitude of the strain rate.

• Structural Engineering and Mechanics
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• 제70권3호
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• pp.339-350
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• 2019

This research focuses on finite element model updating and damage assessment of structures at element level based on global nondestructive test results. For this purpose, an optimization system is generated to minimize the structural dynamic parameters discrepancies between numerical and experimental models. Objective functions are selected based on the square of Euclidean norm error of vibration frequencies and modal assurance criterion of mode shapes. In order to update the finite element model and detect local damages within the structural members, modern optimization techniques is implemented according to the evolutionary algorithms to meet the global optimized solution. Using a simulated numerical example, application of genetic algorithm (GA), particle swarm (PSO) and artificial bee colony (ABC) algorithms are investigated in FE model updating and damage detection problems to consider their accuracy and convergence characteristics. Then, a hybrid multi stage optimization method is presented merging advantages of PSO and ABC methods in finding damage location and extent. The efficiency of the methods have been examined using two simulated numerical examples, a laboratory dynamic test and a high-rise building field ambient vibration test results. The implemented evolutionary updating methods show successful results in accuracy and speed considering the incomplete and noisy experimental measured data.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.385-392
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• 2003

Traditional forms of river and coastal structures have become very expensive to build and maintain, because of the shortage of natural rock. Geotextile tubes hydraulically or mechanically filled with dredged materials have been applied in hydraulic and coastal engineering in recent years(shore protection structure, detached breakwater, groins and jetty). Recently, new preliminary design criteria supported by model and prototype tests, and some stability analysis calculations have been studied. In this study, the numerical analysis was performed to investigate the behavior of geotextile tube with various properties of geotextile and hydraulic pumping conditions. Numerical analysis was executed to compare with the results from the large-scale field model tests, and also compared the results of 2-D plane strain analysis and 3-D FEM analysis. A geotextile tube was modeled using the commercial finite element analysis program ABAQUS and the one-quarter of tube was modeled. Behavior of geotextile tube during the hydraulic pumping procedure was analyzed by comparing the large-scale field model test and numerical analysis. The shape variation and maximum tube height between the numerical analysis results and large-scale filed test results are turned out to be a good agreement.

• 한국수자원학회논문집
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• 제31권2호
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• pp.189-198
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• 1998

Five dam-break floodwave models are t재 field data sets. The models included FLDWAV, SMPDBK, HEC-1, Tr66, and HEC Dimensionless Graph. The field data sets documented the disasters at Teton dam, and Yeunchun dam. The FLDWAV results are uesd to test the sensitivity of the floodwave to variations in Manning's roughness coefficient, breach size, and bottom slope. The HEC-1 analysis includes testing the sensitivity of the results to model parameters. The TR66 model and FLDWAV, with channel routing by TR66 in both cases. SMPDBK and the Dimensionless Graph procedure are applied without particular difficulties being encountered in both real world cases. It is necessary to analyze numerical limit of existing numerical models and then to apply the relatively accurate numerical model in real basin. It is found that FLDWAV model is superior in numerical accuracy and stability to any other model. This study will contribute to improve defect of numerical models and develop more precise numerical model for a efficient and rapid dam breach flood disaster predict.

• Structural Engineering and Mechanics
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• 제17권2호
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• pp.187-201
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• 2004

A shaking table test on a three-story one-bay steel frame model with metallic yield dampers and their parallel connection with oil dampers is carried out to study the dynamic characteristics and seismic performance of the energy dissipation system. It is found from the test that the combined energy dissipation system has favorable reducing vibration effects on structural displacement, and the structural peak acceleration can not evidently be reduced under small intensity seismic excitations, but in most cases the vibration reduction effect is very good under large intensity seismic excitations. Test results also show that stiffness of the energy dissipation devices should match their damping. Dynamic analysis method and mechanics models of these two dampers are proposed. In the analysis method, the force-displacement relationship of the metallic yield damper is represented by an elastic perfectly plastic model, and the behavior of the oil damper is simulated by a velocity and displacement relative model in which the contributions of the oil damper to the damping force and stiffness of the system are considered. Validity of the analytical model and the method is verified through comparison between the results of the shaking table test and numerical analysis.

• Nuclear Engineering and Technology
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• 제48권2호
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• pp.505-517
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• 2016

The structural integrity of a dual-purpose metal cask currently under development by the Korea Radioactive Waste Agency (KORAD) was evaluated, through numerical simulations and a model test, under high-speed missile impact reflecting targeted aircraft crash conditions. The impact conditions were carefully chosen through a survey on accident cases and recommendations from literature. In the impact scenario, a missile flying horizontally hits the top side of the cask, which is freestanding on a concrete pad, with a velocity of 150 m/s. A simplified missile simulating a commercial aircraft engine was designed from an impact loade-time function available in literature. In the analyses, the dynamic behavior of the metal cask and the integrity of the containment boundary were assessed. The simulation results were compared with the test results for a 1:3 scale model. Although the dynamic behavior of the cask in the model test did not match exactly with the prediction from the numerical simulation, other structural responses, such as the acceleration and strain history during the impact, showed very good agreement. Moreover, the containment function of the cask survived the missile impact as expected from the numerical simulation. Thus, the procedure and methodology adopted in the structural numerical analyses were successfully validated.

• International Journal of Reliability and Applications
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• 제6권1호
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• pp.31-39
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• 2005

An economic life test sampling plan for products with exponential lifetime distribution is developed. To reduce test time, a test plan with curtailed Type II censoring is considered. A cost model is constructed which involves three cost components; test cost, accept cost, and reject cost. Determination of optimal plan minimizing the expected average cost per lot is discussed with a constraint related to consumer's risk. Some numerical examples are provided.

• 한국지반환경공학회 논문집
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• 제2권3호
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• pp.89-99
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• 2001

본 연구에서는 가장 널리 사용되고 있는 지반모델인 Modified Cam-Clay 모델을 이용하여 피에조콘 관입 및 소산시험의 수치해석을 수행하였다. Modified Cam-Clay 모델 및 관련 유한요소 식들을 피에조콘 관입의 대변형 현상을 고려하기 위하여 Updated Lagrangian frame에서 formulation 하였다. 유한요소 해석 결과 얻어진 콘 관입저항치, 간극수압 및 소산곡선을 양산지역 현장 시험결과와 비교 분석하였다. 수치해석 결과는 시험결과와 비교적 잘 부합하는 것으로 고찰되었으나 보다 현실에 근접한 simulation을 위하여 연속적인 깊은 관입의 적절한 수치해석적 modeling이 요구되는 것으로 고찰되었다.

• 한국지반환경공학회 논문집
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• 제14권12호
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• pp.61-69
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• 2013

도로 및 철도의 터널 공사가 증가함에 따라 공사 시에 다양한 지반조건에서 터널 공사 단계를 진행하고 있다. 특히, 석회암 지역에서 터널 공사를 진행하게 되는 경우에는 대부분의 공동이 터널 계획구간에 존재하고 있는 실정이다. 하나 또는 그 이상의 공동은 터널의 안정성을 저하하는 것으로 예상된다. 따라서, 본 연구에서는 터널과 공동과의 상호 영향을 알아보고자 실내 모형 축소실험과 수치해석을 시행하였다. 실내모형실험은 터널과 공동 간의 거리에 따른 모형지반의 파괴하중을 확인하였고, 공동의 형상에 따른 파괴하중을 확인하였다. 실내모형실험결과 파괴하중은 공동과 터널 간의 거리가 0.5D 이내로 감소함에 따라서 파괴하중 역시 감소하는 것으로 나타났다. 수치해석은 모형실험의 검증을 위해 시행하였으며, 실내모형실험과 동일하게 터널과 공동 간의 거리가 0.5D 이내로 근접하는 경우 터널의 안정성이 저하되는 것으로 확인되었다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.243-248
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• 1998

This study was performed to obtain a numerical model for a viscous fluid damper from an experimental testing. The input signals for displacement were chosen as two types : a triangular and a sinusoidal forms. The performing test parameters were the area of the resistant plate, relative velocity between resistant plate and base plate, oil film thickness of the viscous fluid, but the temperature effect was neglected. The numerical model was established by assuming an non-Newtonian fluid behavior. The test results were summarized by the equation of F= 0.0308(ν/d)0.5125. Using the obtained for a real structure design was introduced.