• 한국전산구조공학회논문집
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• 제22권3호
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• pp.231-242
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• 2009

스카이브릿지의 연결시스템은 일반적으로 매우 큰 비선형성을 가지고 있으므로 연결된 건물의 동적거동을 정확하게 예측하여 스카이브릿지를 설계하기 위해서는 경계비선형 시간이력해석이 필요하다. 그러나 일반적인 유한요소 해석모델을 사용하여 전체 고층건물을 모형화하고 설계를 위하여 반복적인 경계비선형 시간이력해석을 수행한다면 해석에 소요되는 노력과 시간이 매우 클 것이다. 따라서 본 연구에서는 스카이브릿지로 연결된 고층건물의 효율적인 동적해석 및 진동제어 성능 평가를 위하여 벨트월의 효과를 고려한 등가의 캔틸레버모델을 제안하였다. 제안된 등가모델의 효율성 및 정확성을 검토하기 위하여 스카이브릿지로 연결된 49층과 42층 건물을 예제구조물로 사용하였고 풍하중에 대한 경계비선형 시간이력해석을 수행하였다. 해석결과 제안된 등가모델을 사용하면 스카이브릿지로 연결된 고층건물의 동적응답을 매우 효율적으로 파악할 수 있다는 것을 확인하였다.

• Structural Engineering and Mechanics
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• 제49권4호
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• pp.463-477
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• 2014

In this paper, seismic performance of Kozyatagi Bridge is evaluated by employing nonlinear elasto-plastic dynamic analysis and the deformation-based performance. The time-history records of the 1999 Izmit, 1971 San Fernando and 1989 Loma Prieta earthquakes are modified by adopting a probability of exceedance of 2% in 50 years corresponding to the return period of 2475 years. The analysis is carried out for three different bearing cases which are movable bearings, restrained bearings, and movable bearings with viscous fluid dampers in the radial direction. The analysis results show that the bridge can be retrofitted with viscous fluid dampers. In this case the reinforced concrete piers need not be strengthened by any jacketing techniques in order to preserve the original architectural appearance of the bridge. The retrofitting design of the bridge with viscous fluid dampers is also presented in detail.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 봄 학술발표회 논문집
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• pp.53-60
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• 2002

It has been recognized that damage control must become a more explicit design consideration. In an effort to develop design methods based on performance it is clear that the evaluation of the inelastic response is required. The methods available to the design engineer today are nonlinear time history analyses, or monotonic static nonlinear analyses, or equivalent static analyses with simulated inelastic influences. Some codes proposed the capacity spectrum method based on the nonlinear static(pushover) analysis to determine earthquake-induced demand given the structure pushover curve. This procedure is conceptually simple but iterative and time consuming with some errors. This paper presents a nonlinear direct spectrum method to evaluate seismic Performance of structure, without iterative computations, given the structural initial elastic period and yield strength from the pushover analysis, especially for multi degree of freedom structures. The purpose of this paper is to investigate accuracy and confidence of this method from a point of view of various earthquakes and unloading stiffness degradation parameters.

• Earthquakes and Structures
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• 제11권6호
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• pp.1061-1076
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• 2016

Prefabricated Modular Buildings are increasingly becoming popular in the construction industry as a method to achieve financially economical buildings in a very short construction time. This increasing demand for modular construction has expanded into multi-storey applications where the effect of lateral loads such as seismic loads becomes critical. However, there is a lack of detailed scientific research that has explored the behaviour of modular buildings and their connection systems against seismic loads. This paper will therefore present the nonlinear time history analysis of a multi-storey modular building against several ground motion records. The critical elements that need special attention in designing a modular building in similar seismic conditions is discussed with a deeper explanation of the behaviour of the overall system.

• Earthquakes and Structures
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• 제20권1호
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• pp.97-107
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• 2021

A comprehensive study on seismic performance of wood frame building in hilly regions is presented. Specifically, seismic fragility assessment of a typical wood frame building at various locations of the northeast region of India are demonstrated. A three-dimensional simplified model of the wood frame building is developed with due consideration to nonlinear behaviour of shear walls under lateral loads. In doing so, a trilinear model having improved capability to capture the force-deformation behaviour of shear walls including the strength degradation at higher deformations is proposed. The improved capability of the proposed model to capture the force-deformation behaviour of shear wall is validated by comparing with the existing experimental results. The structural demand values are obtained from nonlinear time history analysis (NLTHA) of the three-dimensional wood frame model considering the effect of uncertainty due to record to record variation of ground motions and structural parameters as well. The ground motion bins necessary for NLTHA are prepared based on the identified hazard level from probabilistic seismic hazard analysis of the considered locations. The maximum likelihood estimates of the lognormal fragility parameters are obtained from the observed failure cases and the seismic fragilities corresponding to different locations are estimated accordingly. The results of the numerical study show that the wood frame constructions commonly found in the region are likely to suffer minor cracking or damage in the shear walls under the earthquake occurrence corresponding to the estimated seismic hazard level; however, poses negligible risk against complete collapse of such structures.

• 대한토목학회논문집
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• 제12권4호
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• pp.33-47
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• 1992

본 논문에서는 케이블로 지지된 프리스트레스트 콘크리트(PC) 뼈대의 시공중의 각 단계를 고려하고 콘크리트와 PC 강재, 케이블 재료의 시간의존적 특성 및 재료의 비선형성과 케이블의 색 및 구조물의 처짐에 의한 기하학적 비선형성도 고려하는 해석방법을 제시했다. 구조물의 비선형거동을 해석하기 위한 운동방정식은 Updated Lagrangian 방식을 이용하여 유도하고 시간의존적인 거동올 해석하기 위해서 시간영역을 시간단계로 나누어 순차적으로 적분했다. 시공중의 각 단계를 표현하기 위해 계속적인 구조계의 변화를 고려했다. 본 논문에서 제시한 해석방법에 근거하여 컴퓨터 프로그램 CFRAME을 개발하고 예제들을 통하여 해석방법의 정당성을 보였다.

• Earthquakes and Structures
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• 제18권2호
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• pp.263-273
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• 2020

The use of energy concepts in seismic analysis and design of structures requires the understanding of the input energy response of multi-degree-of-freedom (MDOF) systems subjected to strong ground motions. For design purposes and non-time consuming analysis, however, it would be beneficial to associate the input energy response of MDOF systems with those of single-degree-of-freedom (SDOF) systems. In this paper, the theoretical formulation of energy input to MDOF systems is developed on the basis that only a particular portion of the total mass distributed among floor levels is effective in the nth-mode response. The input energy response histories of several reinforced concrete frames subjected to a set of eleven horizontal acceleration histories selected from actual recorded events and scaled in time domain are obtained. The contribution of the fundamental mode to the total input energy response of MDOF frames is demonstrated both graphically and numerically. The input energy of the fundamental mode is found to be a good indicator of the total energy input to two-dimensional regular MDOF structures. The numerical results computed by the proposed formulation are verified with relative input energy time histories directly computed from linear time history analysis. Finally, the elastic input energies are compared with those computed from time history analysis of nonlinear MDOF systems.

• 한국지진공학회논문집
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• 제20권7_spc호
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• pp.553-560
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• 2016

After an earthquake occurred in the Gyeongju, 2016, many low-story buildings have been questioned in terms of the seismic performance since mostly they have been exempted from the seismic design requirement since 1988. In this study, a 3-story moment resisting frame (MRF) building was analyzed and evaluated the seismic performance. Due to the insufficient seismic performance required for the seismic performance levels, three different seismic retrofit schemes were proposed and their seismic performances were re-evaluated. While steel brace and open shear wall retrofit systems mainly focused on the strength retrofit, the VES damper retrofit system is mainly to enhance the energy dissipation capacity of the system and resultes in the increased ductility. The original building and 3 retrofitted buildings were evaluated using the nonlinear static and nonlinear dynamic analyses and suggestions were proposed. Through the analysis of nonlinear time history and push-over using MIDAS/Gen program, damages of the building in terms of top story and average story drift and effect of reinforcement were analyzed.

• 교육시설 논문지
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• 제19권4호
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• pp.29-38
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• 2012

Recently large scale earthquake s are occurred around the world following the damage of buildings. So the interest of preparing for earthquake seismic design and seismic performance has becoming high. School buildings are though used for educational purpose; they are also used as emergency shelter for local residents during earthquake disaster. However, the current seismic design ratio of our country (Korea) is 3.7% and if massive earthquake is occurred it follows a serious damage. In order to overcome this situation, seismic performance evaluation is carried out for existing school building and an accurate and appropriate seismic retrofit is required based on performance evaluation to upgrade the existing school buildings. In this paper, nonlinear static analysis on existing school buildings for ATC-40 and FEMA-356 are carried out using the capacity spectrum method to evaluate seismic performance and to determine the need for retrofitting. In addition, after reinforcement to verify the effect of retrofit enhance the seismic performance is applied the seismic performance evaluation is carried out to verify the effect of seismic retrofit time history analysis using nonlinear dynamic analysis is also performed and nonlinear behavior of earthquake load of seismic retrofit of structures was also investigated.

• Earthquakes and Structures
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• 제7권3호
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• pp.271-294
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• 2014

In recent years, along with the advances made in performance-based design optimization, the need for fast calculation of response parameters in dynamic analysis procedures has become an important issue. The main problem in this field is the extremely high computational demand of time-history analyses which may convert the solution algorithm to illogical ones. Two simplifying strategies have shown to be very effective in tackling this problem; first, simplified nonlinear modeling investigating minimum level of structural modeling sophistication, second, wavelet analysis of earthquake records decreasing the number of acceleration points involved in time-history loading. In this paper, we try to develop an efficient framework, using both strategies, to solve the performance-based multi-objective optimal design problem considering the initial cost and the seismic damage cost of steel moment-frame structures. The non-dominated sorting genetic algorithm (NSGA-II) is employed as the optimization algorithm to search the Pareto optimal solutions. The constraints of the optimization problem are considered in accordance with Federal Emergency Management Agency (FEMA) recommended design specifications. The results from numerical application of the proposed framework demonstrate the capabilities of the framework in solving the present multi-objective optimization problem.