• Structural Engineering and Mechanics
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• 제21권3호
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• pp.255-273
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• 2005

Based on the random vibration theory, a response spectrum method is developed for seismic response analysis of linear, multi-degree-of-freedom structures under multi-support excitations is developed. Various response quantities, including the mean and variance of the peak response, the response mean frequency, are obtained from proposed combination rules in terms of the mean response spectrum. This method makes it possible to apply the response spectrum to the seismic reliability analysis of structures subjected to multi-support excitations. Considering that the tedious numerical integration is required to compute the spectral parameters and correlation coefficients in above combination rules, this paper further offers simplified procedures for their computation, which enhance dramatically the computational efficiency of the suggested method. The proposed procedure is demonstrated for tow numerical examples: (1) two-span continuous beam; (2) two-tower cabled-stayed bridge by using Monte Carlo simulation (MC). For this purpose, this paper also presents an approach to simulation of ground motions, which can take into account both mean and variation properties of response spectrum. Computed results based on the response spectrum method are in good agreement with Monte Carlo simulation results. And compared with the MSRS method, a well-developed multi-support response spectrum method, the proposed method has an incomparable computational efficiency.

• 대한조선학회논문집
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• 제51권5호
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• pp.396-408
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• 2014

In this study, uncertainty analysis based on ITTC(International Towing Tank Conference) Recommended Procedures is carried out in the towing-tank experiment for motion responses and added resistance. The experiment was conducted for KVLCC2 model in head sea condition. The heave, pitch and added resistance were measured in different wave conditions, and the measurement was repeated up to maximum 15 times in each wave condition in order to observe the uncertainty of measured data. The uncertainty analysis was carried out by adopting the ISO-GUM(International Organization for Standardization, Guide to the Expression of Uncertainty in Measurements) method recommended by ITTC. This paper describes the details about the analysis method, uncertainty and the measured uncertainty for each source. The uncertainty analysis results are summarized as a tabular form. To validate the accuracy of the present measurement, the experimental results are compared with the results of numerical computation and other experiment. From the present uncertainty analysis, the main sources of uncertainty are identified, which can be very useful to improve the accuracy for added resistance experiment.

• 한국강구조학회 논문집
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• 제11권1호통권38호
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• pp.13-22
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• 1999

본 연구에서는 처짐각법을 개선하여 강박스형교의 뒤틀림 거동을 분석할 수 있는 프로그램을 개발하였다. 박스거더의 뒤틀림 거동을 분석하는 대표적인 방법으로 BEF유사법과 EBEF법이 있으나, 전자는 등단면에 국한되고 경계조건에 따른 적분상수를 계산하기 위해 복잡한 삼각함수를 적용해야 하는 번거로움이 있다. 후자는 격벽의 강성을 무한으로 하여 연속보로 해석하는 근시적인 수치해석 방법이다. 따라서 본 연구에서는 변단면과 격벽의 강성을 해석에 반영할 수 있는 방법을 개발하였다. 몇 가지 예제 해석을 통하여 본 연구에서 개발한 프로그램의 타당성을 검증하였고, 격벽의 강성에 따른 매개변수 연구를 수행하였다.

• Earthquakes and Structures
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• 제8권4호
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• pp.915-934
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• 2015

Within the context of Structural Health Monitoring (SHM), it is often the case that structural systems are described by uncertainty, both with respect to their parameters and the characteristics of the input loads. For the purposes of system identification, efficient modeling procedures are of the essence for a fast and reliable computation of structural response while taking these uncertainties into account. In this work, a reduced order metamodeling framework is introduced for the challenging case of nonlinear structural systems subjected to earthquake excitation. The introduced metamodeling method is based on Nonlinear AutoRegressive models with eXogenous input (NARX), able to describe nonlinear dynamics, which are moreover characterized by random parameters utilized for the description of the uncertainty propagation. These random parameters, which include characteristics of the input excitation, are expanded onto a suitably defined finite-dimensional Polynomial Chaos (PC) basis and thus the resulting representation is fully described through a small number of deterministic coefficients of projection. The effectiveness of the proposed PC-NARX method is illustrated through its implementation on the metamodeling of a five-storey shear frame model paradigm for response in the region of plasticity, i.e., outside the commonly addressed linear elastic region. The added contribution of the introduced scheme is the ability of the proposed methodology to incorporate uncertainty into the simulation. The results demonstrate the efficiency of the proposed methodology for accurate prediction and simulation of the numerical model dynamics with a vast reduction of the required computational toll.

• Computers and Concrete
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• 제7권2호
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• pp.159-167
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• 2010

This paper demonstrates numerical techniques for complex large-scale modeling with microplane constitutive theories for reinforced high strength concrete, which for these applications, is defined to be around the 7000 psi (48 MPa) strength as frequently found in protective structural design. Applications involve highly impulsive loads, such as an explosive detonation or impact-penetration event. These capabilities were implemented into the authors' finite element code, ParaAble and the PRONTO 3D code from Sandia National Laboratories. All materials are explicitly modeled with eight-noded hexahedral elements. The concrete is modeled with a microplane constitutive theory, the reinforcing steel is modeled with the Johnson-Cook model, and the high explosive material is modeled with a JWL equation of state and a programmed burn model. Damage evolution, which can be used for erosion of elements and/or for post-analysis examination of damage, is extracted from the microplane predictions and computed by a modified Holmquist-Johnson-Cook approach that relates damage to levels of inelastic strain increment and pressure. Computation is performed with MPI on parallel processors. Several practical analyses demonstrate that large-scale analyses of this type can be reasonably run on large parallel computing systems.

• Computers and Concrete
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• 제32권6호
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• pp.625-637
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• 2023

The application of ML approaches in determining the resisting capacity of fire damaged RC columns is introduced in this paper, on the basis of analysis data driven ML modeling. Considering the characteristics of the structural behavior of fire damaged RC columns, the representative five approaches of Kernel SVM, ANN, RF, XGB and LGBM are adopted and applied. Additional partial monotonic constraints are adopted in modelling, to ensure the monotone decrease of resisting capacity in RC column with fire exposure time. Furthermore, additional suggestions are also added to mitigate the heterogeneous composition of the training data. Since the use of ML approaches will significantly reduce the computation time in determining the resisting capacity of fire damaged RC columns, which requires many complex solution procedures from the heat transfer analysis to the rigorous nonlinear analyses and their repetition with time, the introduced ML approach can more effectively be used in large complex structures with many RC members. Because of the very small amount of experimental data, the training data are analytically determined from a heat transfer analysis and a subsequent nonlinear finite element (FE) analysis, and their accuracy was previously verified through a correlation study between the numerical results and experimental data. The results obtained from the application of ML approaches show that the resisting capacity of fire damaged RC columns can effectively be predicted by ML approaches.

• Earthquakes and Structures
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• 제27권3호
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• pp.209-226
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• 2024

The susceptibility of Reinforced Concrete (RC) buildings to earthquake-induced damage is a critical concern, primarily attributed to their inadequate seismic performance. The existing earthquake-resistant design code of India prescribes guidelines to minimize seismic damage but does not provide any means for evaluating the actual seismic performance and damage. To ascertain the seismic performance of the structures quantitatively, it is crucial to classify damage into measurable damage states. Damage Index (DI) acts as an important tool for this purpose. Among various procedures for computation of DI, the modified Park and Ang Damage Index appears to be highly accurate. However, the major drawback of this method is that it is lengthy and time-consuming. On the other hand, structural performances can be evaluated using various performance parameters such as interstory drift ratio (IDR), inelastic deformation, etc., as described in FEMA-356 and ASCE-41 17. The present study explores the correlation between seismic DI and structural performance in RC frame buildings designed according to IS code. Sixteen building models, incorporating diverse configurations, are examined using nonlinear static and time history analyses. A simplified equation is developed by regression analysis to predict DI based on IDR, offering a computationally efficient alternative. Validation tests are done to confirm the equation's accuracy. Furthermore, a unified damage scale integrating DI and seismic performance is also proposed for seismic damage evaluation of buildings designed by IS code.

• 한국방재학회 논문집
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• 제10권5호
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• pp.149-158
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• 2010

최근 우리나라의 강수량과 호우의 발생 일수는 증가 추세를 보이고 있다. 이에 따라 홍수 재해의 피해액도 증가하고 있다. 본 연구에서는 SWMM과 FLUMEN 모형을 이용하여 부산의 수영과 망미 지구에 대한 침수 상황을 분석하였다. 수영과 망미 지구는 1995년 이래 침수위험지구였다. 이 지역의 최근 침수는 2009년 7월 7일과 16일의 호우에 의하여 발생하였고, 본 연구에서는 16일의 침수 상황을 분석하였다. 계산의 첫 번째 단계는 SWMM을 이용하여 우수관거를 흐르는 홍수 수문 곡선을 산정하는 것이다. 관거의 용량을 초과하여 범람한 유량은 FLUMEN을 이용하여 침수 분석에 사용되었다. 침수 분석의 결과는 연구 지역의 실제 침수 상황과 비교 분석되었다. 실제 최대 침수심은 7월 16일에 1.0 m 정도일 것으로 추정된다. 그에 반해 계산 결과는 최대 침수심이 약 1.2 m에 이르러, 다소 크게 추정하고 있다. 오차의 원인은 홍수유출량 산정의 오차와 FLUMEN을 이용한 모의에서 건물의 지하층으로 유입된 수량을 적절히 반영하지 못한 것 때문으로 추정된다. 본 연구에서 침수 분석에 사용한 모형과 일련의 분석 과정은 호우에 따른 침수와 배수 능력을 검토하는 데 적용될 수 있다.

• 비파괴검사학회지
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• 제25권2호
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• pp.110-116
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• 2005

비젼시스템을 검사, 물체위치 결정 및 용접 작업등에 실시간 응용하고자할 때 CCD카메라에서 얻어진 많은 데이터를 처리해야 하기 때문에 전산처리 속도를 줄이는 것이 매우 중요하다. 또한, 비젼시스템 모델에 포함되어 있는 매개변수를 추정하는데 있어서 Newton-Raphson 방법 같은 반복적인 기법을 사용하면 많은 전산처리 시간을 필요하게 되어 실시간 응용을 어렵게 한다. 위의 문제점을 해결하기 위해 확장칼만필터링 같은 효율적인 방법이 필요하다. 확장칼만필터링 방법은 CCD카메라로부터 얻어지는 측정데이터의 불확실성을 고려할 뿐만 아니라, 순환적인 처리 기법을 사용하므로 전산처리 속도 향상을 가져온다. 이리하여 본 연구는 비젼시스템 모델에 포함된 카메라 내부 및 외부 매개변수를 설명하는 6개 매개변수 추정과 이를 이용한 물체 치수를 추정하는데 확장칼만필터링 방법을 적용하였다. 마지막으로 개발된 추정기법의 실시간 적용의 타당성을 실험을 통하여 보였다.

• 방송공학회논문지
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• 제15권6호
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• pp.731-741
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• 2010

본 논문에서는 30 MHz ~ 3000 MHz 대역에서 1 kW ERP에 대해 점-대-지역 전파특성 예측에 이용되는 ITU-R 권고 P.1546 전파 모델을 이용하여 DTV 수신기의 전계강도 예측을 위한 방법을 제안한다. DTV 수신기의 유도된 전계강도 수식과 권고에서 기술된 절차를 이용하여 수치계산을 통한 결과를 제시한다. 또한 산출된 결과의 적절성 검증을 위해 Okumura-Hata 모델과 비교하였으며, 수신 전계강도가 약 6.9 ~ 11.5 % 범위 내에 오차가 있음을 확인할 수 있었다. 제시된 방법은 DTV 수신지역의 전계강도 예측을 통한 송신된 신호의 품질 분석은 물론, 양호한 전파환경 구축을 위한 적절한 국소 선정을 제공한다. 또한 동일 대역의 주파수 공유를 위한 보호비 또는 이격 거리 분석에도 직접 활용이 가능하다.