• Earthquakes and Structures
• /
• 제1권1호
• /
• pp.109-127
• /
• 2010

This work aims at introducing structural sensitivity analysis capabilities into existing commercial finite element software codes for the purpose of mapping retrofit strategies for a broad group of structures including heritage-type buildings. More specifically, the first stage sensitivity analysis is implemented for the standard deterministic environment, followed by stochastic structural sensitivity analysis defined for the probabilistic environment in a subsequent, second phase. It is believed that this new generation of software that will be released by the industrial partner will address the needs of a rapidly developing specialty within the engineering design profession, namely commercial retrofit and rehabilitation activities. In congested urban areas, these activities are carried out in reference to a certain percentage of the contemporary building stock that can no longer be demolished to give room for new construction because of economical, historical or cultural reasons. Furthermore, such analysis tools are becoming essential in reference to a new generation of national codes that spell out in detail how retrofit strategies ought to be implemented. More specifically, our work focuses on identifying the minimum-cost intervention on a given structure undergoing retrofit. Finally, an additional factor that arises in earthquake-prone regions across the world is the random nature of seismic activity that further complicates the task of determining the dynamic overstress that is being induced in the building stock and the additional demands placed on the supporting structural system.

• 한국터널지하공간학회 논문집
• /
• 제18권6호
• /
• pp.569-579
• /
• 2016

국내 터널 갱구사면에 안정성을 확보하기 위한 사면보강은 앵커, 쏘일네일 및 록볼트 등을 이용한 다양한 공법이 사용되고 있다. 갱구 사면보강공법 및 보강재 배치, 보강재 길이 등을 선정하기 위해서는 시행착오법 등 시간이 많이 소요되기도 하며, 최적조건의 상태가 선정되었는지에 대한 검증이 쉽지 않은 경우도 발생한다. 본 연구에서는 FLAC3D 프로그램에 내장된 FISH 언어를 사용해서, 차분진화 알고리즘(DEA)을 적용한 최적화기법을 개발하였다. 갱구사면 보강공법 중에 쏘일네일링 공법에 대한 데이터베이스를 구축한 후, FLAC3D 해석을 통한 안전율 기반의 최적보강배치 계획을 선정할 수 있도록 하였다. 수치해석 결과, 완전조합(FC)에 비해서 DEA 기반의 최적화기법이 해석회수가 8배 정도 감소함을 확인하였다. 갱구 사면보강 설계 시 개발된 시스템을 활용하면, 최적보강배치 계획을 상대적으로 쉽게 선정할 수 있을 것으로 기대된다.

• Smart Structures and Systems
• /
• 제3권3호
• /
• pp.245-261
• /
• 2007

Nonlinear time-domain system identification (SI) algorithm is proposed to assess damage in a shear building by synchronously estimating time-varying stiffness and damping parameters using measured acceleration data. Mass properties have been assumed as the a priori known information. Viscous damping was utilized for the current research. To chase possible nonlinear dynamic behavior under severe vibration, an incremental governing equation of vibrational motion has been utilized. Stiffness and damping parameters are estimated at each time step by minimizing the response error between measured and computed acceleration increments at the measured degrees-of-freedom. To solve a nonlinear constrained optimization problem for optimal structural parameters, sensitivities of acceleration increment were formulated with respect to stiffness and damping parameters, respectively. Incremental state vectors of vibrational motion were computed numerically by Newmark-${\beta}$ method. No model is pre-defined in the proposed algorithm for recovering the nonlinear response. A time-window scheme together with Monte Carlo iterations was utilized to estimate parameters with noise polluted sparse measured acceleration. A moving average scheme was applied to estimate the time-varying trend of structural parameters in all the examples. To examine the proposed SI algorithm, simulation studies were carried out intensively with sample shear buildings under earthquake excitations. In addition, the algorithm was applied to assess damage with laboratory test data obtained from free vibration on a three-story shear building model.

• 한국공간구조학회논문집
• /
• 제20권2호
• /
• pp.51-58
• /
• 2020

Recently, deep learning that is the most popular and effective class of machine learning algorithms is widely applied to various industrial areas. A number of research on various topics about structural engineering was performed by using artificial neural networks, such as structural design optimization, vibration control and system identification etc. When nonlinear semi-active structural control devices are applied to building structure, a lot of computational effort is required to predict dynamic structural responses of finite element method (FEM) model for development of control algorithm. To solve this problem, an artificial neural network model was developed in this study. Among various deep learning algorithms, a recurrent neural network (RNN) was used to make the time history response prediction model. An RNN can retain state from one iteration to the next by using its own output as input for the next step. An eleven-story building structure with semi-active tuned mass damper (TMD) was used as an example structure. The semi-active TMD was composed of magnetorheological damper. Five historical earthquakes and five artificial ground motions were used as ground excitations for training of an RNN model. Another artificial ground motion that was not used for training was used for verification of the developed RNN model. Parametric studies on various hyper-parameters including number of hidden layers, sequence length, number of LSTM cells, etc. After appropriate training iteration of the RNN model with proper hyper-parameters, the RNN model for prediction of seismic responses of the building structure with semi-active TMD was developed. The developed RNN model can effectively provide very accurate seismic responses compared to the FEM model.

• Smart Structures and Systems
• /
• 제15권1호
• /
• pp.191-207
• /
• 2015

Proper placement of sensors plays a key role in construction and implementation of an effective structural health monitoring (SHM) system. This paper proposes a novel methodology called the distributed monkey algorithm (DMA) for the optimum design of SHM system sensor arrays. Different from the existing algorithms, the dual-structure coding method is adopted for the representation of design variables and the single large population is partitioned into subsets and each subpopulation searches the space in different directions separately, leading to quicker convergence and higher searching capability. After the personal areas of all subpopulations have been finished, the initial optimal solutions in every subpopulation are extracted and reordered into a new subpopulation, and the harmony search algorithm (HSA) is incorporated to find the final optimal solution. A computational case of a high-rise building has been implemented to demonstrate the effectiveness of the proposed method. Investigations have clearly suggested that the proposed DMA is simple in concept, few in parameters, easy in implementation, and could generate sensor configurations superior to other conventional algorithms both in terms of generating optimal solutions as well as faster convergence.

• 한국전산구조공학회논문집
• /
• 제27권4호
• /
• pp.231-238
• /
• 2014

건물의 경우, 용도 변경에 따른 중력하중 변화, 시공 단계에 따라 중력하중 변화 등이 구조물 시스템에 영향을 미친다. 따라서, 본 연구에서는 시스템 식별 변수 설정에 있어 기존에 강성만을 변수로 설정한 방법에 추가적으로 질량을 변수로 설정하여 시스템을 식별하는 기법을 제안한다. 계측한 동특성과 FE모델에서 추출한 동특성 간의 차이를 최소화하여 변수를 탐색하게 된다. 최소화 기법으로 변형 유전 알고리즘을 적용하였다. 보다 전역적 해탐색을 위해 변형 유전 알고리즘은 더 넓은 해 탐색 공간에서 해를 찾는다. 철골 보 구조물의 시뮬레이션을 통해 본 연구가 제시한 기법을 검증하였고 변형 유전 알고리즘과 기존의 단순 유전 알고리즘의 성능을 비교하였다. 또한, 강성 식별만을 수행한 기존 연구의 방법과 본 연구가 제시한 기법간의 차이를 비교하였다.

• 한국지반환경공학회 논문집
• /
• 제15권7호
• /
• pp.13-21
• /
• 2014

최근 우면산 산사태, 춘천지역 산사태, 황령산 터널 입구 산사태 등 국내의 급경사지 붕괴에 따른 사고가 빈번히 발생하고 있으며, 그 규모가 점차 커지고 있는 추세이다. 또한 이에 따른 인명 재산피해가 증가하고 있다. 이에 따라 소방방재청에서는 급경사지 방재를 위한 DB 구축을 통하여 급경사지 붕괴 예측 및 신속한 대응체계 구축을 위한 급경사지 통합관제시스템 구축을 추진하고 있다. 급경사지 방재와 관련된 정보로는 급경사지 일제조사서를 기반으로 한 사면정보와 지반, 지질 등의 지하공간정보가 있으며, 이 중 국가재난관리시스템을 통한 텍스트 기반의 간단한 급경사지 정보 외 나머지 정보는 구축되어 있지 않아 급경사지 방재 DB 구축이 매우 시급한 실정이다. 따라서 본 연구에서는 급경사지 방재 DB 구축방법과 활용방안을 제시하였다. 급경사지 방재 DB 중 급경사지 일제조사서 기반의 사면 DB는 기존 일제조사서의 문제점 분석을 개선한 급경사지 일제조사서를 기반으로 하는 웹 급경사지 입력시스템을 통한 DB 구축방법을 제시하였으며, 지하공간정보의 경우 국토교통부(국토지반정보 통합 DB 센터)와 소방방재청(국가지진방재 통합정보시스템) 사이의 지하공간정보 실시간 연계체계로 관리되는 지진방재용 지하공간정보 중 급경사지 부분의 지하공간정보 DB 구축방법을 제시하였다. 또한 급경사지 방재 DB의 활용방안은 현재 소방방재청에서 구축 중인 U-IT 기반의 급경사지 통합관리시스템, 급경사지 붕괴 위험도 판단시스템 등으로의 활용방안을 제시하였다.

• Wind and Structures
• /
• 제26권2호
• /
• pp.69-74
• /
• 2018

Nowadays, using math logic in great civil projects is considered by the clients to achieve the goals of project including quality optimization, costs, avoiding individual, emotional and political decision making, long-term and short-term goals and they are the main requirements of each project and should be considered by the decision makers to avoid the illogical decision making applied on the majority of civil projects and this imposes great financial and spiritual costs on our country. The present study attempts to present one of the civil projects (Ghasre Shirin storage dam) whose client was not ministry of energy for the first time and the short-term and long-term goals of the private sector were applied based on the triangle of quality, cost and time. Also, the math logic and model (multi-criteria decision making method and decision making matrix) is used in one of the most important sections of project, sealing element, policies and new materials (Geosynthetics) are considered and this leads to suitable decision making in this regard. It is worth to mention that this method is used for other sections of a dam including body, water diversion system, diaphragm and other sectors or in other civil projects of building, road construction, etc.

• 신재생에너지
• /
• 제2권3호
• /
• pp.15-22
• /
• 2006

As the distributed generation becomes more reliable and economically feasible, it is expected that a higher application of the distributed generation units would be interconnected to the existing grids. This new market penetration using the distributed generation technology is linked to a large number of factors like economics and performance, safety and reliability, market regulations, environmental issues, or grid connection standards. KEPCO, a government company in Korea, has performed the project to identify and evaluate the performance of Micro Gas Turbine(MGT) technologies focused on 30, 60kW-class grid-connected optimization and combined Heat & Power performance. This paper describes the results for the mechanical, electrical, and environmental tests of MGT on actual grid-connection under Korean regulations. As one of the achievements, the simulation model of Exhaust-gas Absorption Chiller was developed, so that it will be able to analyze or propose new distributed generation system using MGT. In addition, KEPCO carried out the field testing of the MGT Cogeneration system at the R&D Center Building, KEPCO. The field test was conducted in order to respond to a wide variety of needs for heat recovery and utilization. The suggested method and experience for the evaluation of the distributed generation will be used for the introduction of other distributed generation technologies into the grid in the future.

• 한국정보과학회논문지:시스템및이론
• /
• 제37권5호
• /
• pp.257-271
• /
• 2010

Photolithography 통합 시대의 끝이 빠르게 다가옴에 따라, 최근에는 새로운 나노 스케일의 소재와 집적 방식에 기반을 둔 수많은 나노 스케일 장치와 시스템이 나타나고 있다. 특히 nanowire crossbar 구조를 이용한 다양한 reconfigurable architecture 들이 보고되고 있다. 하지만 아쉽게도 나노 스케일의 구성 요소를 이용한 이러한 고집적 시스템은 생산 단계에서 발생하는 각종 물리적 결함과 오차에 취약하며 따라서 결함에 대한 관용성 즉 defecttolerance는 nanowire reconfigurable crossbar 시스템에 있어 해결해야 할 가장 중대한 문제 중 하나라 할 수 있다. 이에 본 논문에서는 nanowire reconfigurable crossbar 시스템 상에서 사용되어질 수 있는 세 가지의 결함 회피형(defectavoidant) 로직 재할당 알고리듬을 설명하고 다양한 방식으로 평가하였다. 이에 더불어 로직 재할당시에 발생하는 비용과 이로 인해 얻어지는 repair performance를 계량적으로 상호 분석하여 최적화된 repair 방식을 찾아내는 새로운 방안을 소개하였다. 이어 다양한 파라메터들을 이용한 시뮬레이션 결과를 제시함으로써 새로 소개된 cost-driven repair 최적화 방식을 검증하였다.