• 한국지진공학회논문집
• /
• 제11권3호
• /
• pp.43-52
• /
• 2007

본 논문에서는 기존 도로교의 합리적이고 일관적인 내진성능향상 방법 선정을 위한 가중치 평가기법을 제안하였다. 한반도의 증가하는 지진위험도를 반영하여, 현재 기존교량의 내진성능향상 작업이 다양한 공법을 이용하여 진행 중이나 최적의 공법을 선정하기 위한 적절한 판단기준이 부재한 형편이다. 이에 제안한 기존가중치 평가기법은 구조적 적합성, 경제성, 환경적 영향, 시공성, 유지관리 측면의 다섯 가지 영향인자의 가중치를 부여하여 최적의 내진 보강방안을 선정하는 방법이다. 제안된 가중치 평가기법을 공용중인 도로교 160개교에 적용한 결과 최고점수는 실제 최종 보강방안과 대부분 일치하여 적절한 가중치로 설정되었다고 판단된다. 제안하는 방법을 기존교량의 내진 보강방안 선정 시에 활용한다면, 사회적 비용을 최소화하는 보다 합리적이고 일관적인 보강이 가능할 것이다.

• Earthquakes and Structures
• /
• 제9권3호
• /
• pp.563-576
• /
• 2015

Over the past few decades, seismic retrofitting of structural systems has been significantly improved by the adoption of various methods such as FRP composite wraps, base isolation systems, and passive/active damper control systems. In parallel with this trend, probabilistic risk assessment (PRA) for structural and nonstructural components has become necessary for risk mitigation and the achievement of reliable designs in performance-based earthquake engineering. The primary objective of the present study was to evaluate the effect on piping fragility at T-joints due to seismic retrofitting of structural systems with passive energy-dissipation devices (i.e., linear viscous dampers). Three mid-rise building types were considered: without any seismic retrofitting; with distributed damper systems; with optimal placement of dampers. The results showed that the probability of piping system failure was considerably reduced in a Multi Degree of Freedom (MDOF) building retrofitted with optimal passive damper systems at lower floor levels. This effect of damper systems on piping fragility became insignificant as the floor level increased.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2004년도 가을 학술발표회 논문집
• /
• pp.379-386
• /
• 2004

The optimal seismic retrofitting of NPP(Nuclear Power Plant) cabinet structures that contained class 1 relays were studies in this paper. During earthquake event, the failure modes of relays are not appeared in form of structural failure, but are appeared in form of contact chatter of relay. Therefore, the retrofitting of cabinet has to be aimed to the reducing of the structural response, such as acceleration. In this study, the optimal characteristic values of dampers were searched by μ-GA (micro-Genetic Algorithm) scheme for several installation patterns. To keep accuracy and efficiency of analysis, the structural models of cabinet were considered as a frame structure. The responses of structure were obtained in form of acceleration response spectra derived from the results of nonlinear time history analysis including damping nonlinearity. The fitness function of the optimum procedure was constructed based on the ratio of maximum spectral value and target GERS (General Equipment Ruggedness Spectra). The results show the good improvements of fitness fur adequate retrofitting pattern. Especially, the improvements of fitness were remarkable when the damping exponents are proper.

• Earthquakes and Structures
• /
• 제14권1호
• /
• pp.1-10
• /
• 2018

Seismic retrofitting of existing buildings and design of earth-quake resistant buildings are important issues associated with earthquake-prone zones. Use of metallic-yielding dampers as an energy dissipation system is an acceptable method for controlling damages in structures and improving their seismic performance. In this study, the optimal distribution of dampers for reducing the seismic response of steel frames with multi-degrees freedom is presented utilizing the uniform distribution of deformations. This has been done in a way that, the final configuration of dampers in the frames lead to minimum weight while satisfying the performance criteria. It is shown that such a structure has an optimum seismic performance, in which the maximum structure capacity is used. Then the genetic algorithm which is an evolutionary optimization method is used for optimal arrangement of the steel dampers in the structure. In continuation for specifying the optimal accurate response, the local search algorithm based on the gradient concept has been selected. In this research the introduced optimization methods are used for optimal retrofitting in the moment-resisting frame with inelastic behavior and initial weakness in design. Ultimately the optimal configuration of dampers over the height of building specified and by comparing the results of the uniform deformation method with those of the genetic algorithm, the validity of the uniform deformation method in terms of accuracy, Time Speed Optimization and the simplicity of the theory have been proven.

• Earthquakes and Structures
• /
• 제16권4호
• /
• pp.375-389
• /
• 2019

During earthquakes, the performance of structures needs to be evaluated, which provides guidance for selecting suitable retrofitting schemes. The purpose of this paper is to accomplish seismic assessment of a simple steel residential building. Once the responses of the system are determined, the scope of the study extends to evaluate selected retrofitting strategies that are intended to rehabilitate the flaws of the structure under prescribed ground motions with high probability of occurrence at the site. After implementing the retrofits, seismic assessment of the upgraded structure is carried out to check if the remediation at various seismic performance levels is acquired or not. Outcomes obtained from retrofitted scenarios are compared to the results obtained from the initial un-retrofitted configuration of the structure. This paper presents the process for optimal selection of rehabilitation solutions considering the cost of implementation, downtime and disruption to property owners while improving the seismic performance level of the structure.

• 한국지진공학회논문집
• /
• 제9권1호통권41호
• /
• pp.1-7
• /
• 2005

본 논문에서는 원전내부의 내진범주 1급 계전기를 포함하고 있는 캐비닛 구조물의 최적내진보강에 대한 연구를 수행하였다. 지진시 계전기는 구조적인 파괴보다는 떨림에 의한 기능적 파괴가 발생한다. 이를 방지하기 위해서는 캐비닛구조물의 응답을 적정 수준이하로 감소시켜야 하므로 다양한 감쇠보강의 설치패턴에 따라 최적의 감쇠계수를 ${\mu}$-GA(micro-Genetic Algorithm)기법을 이용하여 산정하였다. 대상캐비닛 구조물은 해석의 정확도와 계산의 효율성을 만족시키기 위해 이용한 프레임구조로 모델링되었다. 구조물의 응답은 감쇠기의 비선형거동을 고려한 비선형 시간이력해석에 의해 얻어진 가속도응답스펙트럼으로 나타내었다. 목적함수는 구조물의 해석에서 얻어진 응답스펙트럼의 최대값과 목표 포괄기기내진력 스펙트럼 (GERS; General Equipment Ruggedness Spectra)의 최대응답비를 기초로 작성되었다. 해석결과 적절한 보강패턴을 선정한 경우 좋은 적합도의 향상을 보였으며 특히 감쇠지수의 값이 작은 경우 적합도의 개선효과가 뛰어났다.

• Earthquakes and Structures
• /
• 제1권3호
• /
• pp.307-326
• /
• 2010

This paper is concerned with the optimal seismic design of added viscous dampers in yielding plane frames. The total added damping is minimized for allowable values of local performance indices under the excitation of an ensemble of ground motions in both regular and irregular structures. The local performance indices are taken as the maximal inter-story drift of each story and/or the normalized hysteretic energy dissipated at each of the plastic hinges. Gradients of the constraints with respect to the design variables (damping coefficients) are derived, via optimal control theory, to enable an efficient first order optimization scheme to be used for the solution of the problem. An example of a ten story three bay frame is presented. This example reveals the following 'fully stressed characteristics' of the optimal solution: damping is assigned only to stories for which the local performance index has reached the allowable value. This may enable the application of efficient and practical analysis/redesign type methods for the optimal design of viscous dampers in yielding plane frames.

• Structural Engineering and Mechanics
• /
• 제32권1호
• /
• pp.147-165
• /
• 2009

This study proposes a certain measure or investment strategy for decision making associated with seismic retrofitting. This strategy reduces the risk of a large-scale malfunction such as water supply loss under seismic risks. The authors developed a stochastic value index that will be used in the overall evaluation of social benefit, income gain, life cycle costs and failure compensation associated with existing lifeline systems damaged by an earthquake during the remaining service period. Optimal seismic disaster prevention investment of deteriorated lifeline systems is discussed. Finally, the present study provides a performance-based design method for seismic retrofitting strategies of existing lifelines which are carried out using the target probabilities of value loss and structural failure.

• Earthquakes and Structures
• /
• 제9권1호
• /
• pp.29-48
• /
• 2015

The main purpose of this work is to compare different criteria for the seismic strengthening of RC framed buildings in order to find the optimal combinations of these retrofitting techniques. To this end, a numerical investigation is carried out with reference to the town hall of Spilinga (Italy), an RC framed structure with an L-shaped plan built at the beginning of the 1960s. Five structures are considered, derived from the first by incorporating: carbon fibre reinforced polymer (FRP)-wrapping of all columns; base-isolation, with high-damping-laminated-rubber bearings (HDLRBs); added damping, with hysteretic damped braces (HYDBs); FRP-wrapping of the first storey columns combined with base-isolation or added damping. A three-dimensional fibre model of the primary and retrofitted structures is considered; bilinear and trilinear laws idealize, respectively, the behaviour of the HYDB, providing that the buckling be prevented, and the FRP-wrapping, without resistance in compression, while the response of the HDLRB is simulated by using a viscoelastic linear model. The effectiveness of the retrofitting solutions is tested with nonlinear dynamic analyses based on biaxial accelerograms, whose response spectra match those in the Italian seismic code.

• Smart Structures and Systems
• /
• 제4권5호
• /
• pp.685-696
• /
• 2008

This paper deals with the numerical model of a bracing-friction damper system and its deployment using the optimal slip load distribution for the seismic retrofitting of a damaged building. The Slotted Bolted Connection (SBC) type friction damper system was tested to investigate its energy dissipation characteristic. Test results coincided with the numerical ones using the conventional model of a bracing-friction damper system. The placement of this device was numerically explored to apply it to the assumed damaged-building and to evaluate its efficiency. It was found by distributing the slip load that minimizes the given performance indicies based on structural response. Numerical results for the damaged building retrofitted with this slip load distribution showed that the seismic design of the bracing-friction damper system under consideration is effective for the structural response reduction.