• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.198-201
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• 2006

In order to evaluate the seismic performance of reinforced concrete bridge piers, an inelastic time-dependent element is proposed. The proposed element enables increased characteristics due to structural intervention (i.e., repair and retrofitting) to be accurately reflected to the degraded strength and stiffness of the members. Comparative studies are conducted for reinforced concrete bridge columns being repaired and retrofitted and show good correlation between analytical prediction and experimental results. In addition, a nonlinear time-history analysis of a reinforced concrete bridge under multiple earthquakes confirms the applicability and effectiveness of the present development.

• 한국터널지하공간학회 논문집
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• 제18권2호
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• pp.119-128
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• 2016

성능기반 설계에서 구조물의 안정성은 손상 상태와 이를 수치화한 손상 지수에 의해 평가한다. 지상 구조물에 대해서는 이들이 비교적 명확하게 정의되어 있으나 지중 구조물에 대한 연구 수행 사례는 매우 제한적이다. 본 연구에서는 국내 지하철 시스템에 널리 사용되는 박스형 개착식 터널에 작용하는 지진하중에 의한 손상 상태와 손상 지수를 일련의 비탄성 프레임 해석을 통하여 규명하였다. 터널의 3 단계 손상 상태는 구조물에 발생한 소성 힌지의 수에 의해 정의하였다. 손상 지수는 터널 구조 부재의 탄성 모멘트와 항복 모멘트의 비로 정의하여 탄성 해석만으로도 비탄성 거동과 파괴 메커니즘의 모사가 가능하도록 하였다. 또한 손상 지수를 자유장 전단 변형률의 함수로도 제시하였다. 전단 변형률은 1 차원 지반응답해석으로 쉽게 계산할 수 있으므로 이를 이용하여 간편하게 박스형 터널의 초기 내진 안정성 평가가 가능할 것으로 판단된다. 보다 일반적이고 보편적인 적용성 확보를 위해서는 추후 포괄적인 해석을 수행하여 다양한 형태의 터널과 지반에서의 전단 변형률 분포와 불확실성에 대한 연구가 진행되어야 할 것이다. 본 연구에서 제시된 터널 내진설계를 위한 손상 상태, 손상 지수, 그리고 전단파 속도 및 전단변형률 간의 상호관계 플래트폼은 새로운 아이디어를 담고 있으며 추후 설계에 널리 활용될 수 있을 것으로 판단된다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 봄 학술발표회 논문집
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• pp.211-218
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• 2003

Most structures are expected to deform beyond the limit of linearly elastic behavior when subjected to strong ground motion. Seismic evaluation of structure requires an estimation of the structural performance in terms of displacement demand imposed by earthquakes on the structure. Nonlinear response history analysis(NRHA) is the most rigorous procedure to compute seismic performance among various inelastic analysis methods. But nonlinear analysis procedures necessitate more practical and reliable tools for predicting seismic behavior of structures. This paper presents a nonlinear direct spectrum method(NDSM) to evaluate seismic performance of structures, without iterative computations, given by the structural initial elastic period and yield strength from the pushover analysis, especially for MDF(multi degree of freedom) system. The purpose of this paper is to investigate the accuracy and reliability of this method from a point of view of various earthquakes and structure parameters.

• 산업기술연구
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• 제26권A호
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• pp.163-171
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• 2006

To evaluate inelastic seismic responses of multi-span-bridge, the equivalent single-degree-of-freedom (ESDOF) methods and the lateral load distributions are applied to the capacity spectrum method(CSM). From the pushover analysis results using the four ESDOF methods and the six types lateral load distributions, the ESDOF method more than lateral load distribution is found to have an important influence upon the pushover analysis. The effects of the higher mode on the bridge seismic behaviors are also increased as the number of pier increase. Therefore, it can be concluded that lateral load distributions and ESDOF methods for reflection of higher mode effects should be considered in the seismic analysis of the bridge structural.

• Earthquakes and Structures
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• 제10권2호
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• pp.463-482
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• 2016

Air Traffic Control (ATC) towers play significant role in the functionality of each airport. In spite of having complex dynamic behavior and major role in mitigating post-earthquake problems, less attention has been paid to the seismic performance of these structures. Herein, seismic response of an existing ATC tower with a wall-frame structural system that has been designed and detailed according to a local building code was evaluated through the framework of performance-based seismic design. Results of this study indicated that the linear static and dynamic analyses used for the design of this tower were incapable of providing a safety margin for the required seismic performance levels especially when the tower was subjected to strong ground motions. It was concluded that, for seismic design of ATC towers practice engineers should refer to a more sophisticated seismic design approach (e.g., performance-based seismic design) which accounts for inelastic behavior of structural components in order to comply with the higher seismic performance objectives of ATC towers.

• 전산구조공학
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• 제9권4호
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• pp.229-237
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• 1996

구조물의 내진설계는 일반적으로 설계시방서의 스펙트럼을 이용하여 이루어지고 있다. 각 시방서에서 제시된 스펙트럼은 여러지역에서 발생한 지진파들을 최대 지반가속도로 정규화하여 평탄한 응답을 구하였으며, 구조물의 특성에 따라 증감하여 사용하고 있다. 구조물은 지진하중에 의하여 소성변형을 보이고 있으며, 이러한 구조물의 소성변형 능력을 고려하여 설계시방서에서는 응답수정계수를 사용하고 있다. 그러나, 이러한 응답수정계수는 모든 구조물의 고유진동주기에 대하여 일정한 값으로 사용되고 있다. 본 연구에서는 각각의 지진파에 대하여 20개의 인공지진파을 작성하여 평탄한 응답스펙트럼을 구하였다. 구하여진 평균 응답 스펙트럼을 사용하여 구조물의 초기항복강도와 감쇠율의 효과를 측정하였으며, 회기분석을 통하여 내진설계시 각 구조물에 요구되는 변위연성도를 얻기 위한 강도계수를 추정하였다. 또한 현재 사용되고 있는 설계시방서의 응답수정계수를 구조물 고유진동주기의 함수로 나타내었다.

• Structural Engineering and Mechanics
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• 제46권5호
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• pp.695-711
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• 2013

It is reasonable to assume that reinforced concrete (RC) structures enter the nonlinear range of response during a severe ground motion. Numerical analysis to predict the behaviour therefore must allow for the presence of nonlinear deformations if an accurate estimate of seismic response is aimed. Among the factors contributing to inelastic deformations, the influence of the degradation of the bond slip phenomenon is important. Any rebar slip generates an additional rotation at the end regions of structural members which are not accounted for in a conventional analysis. Although these deformations could affect the seismic response of RC structures considerably, they are often neglected due to the unavailability of suitable models. In this paper, the seismic response of two types of RC structures, designed according to the Iranian concrete code (ABA) and the Iranian seismic code (2800), are evaluated using nonlinear dynamic and static analyses. The investigation is performed using nonlinear dynamic and static pushover analysis considering the deformations due to anchorage slip. The nonlinear analysis results confirm that bond slip significantly influences the seismic behavior of RC structure leading to an increase of lateral deformations by up to 30% depending on the height of building. The outcomes also identify important parameters affecting the extent of this influence.

• 한국지진공학회논문집
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• 제11권6호
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• pp.53-61
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• 2007

NEHRP 지반조건 B,C,D에서 이선형 단자유도 감쇠시스템의 지반조건, 후탄성기울기, 감쇠비, 항복강도 감소계수, 고유 주기 등의 변화가 비탄성변위비에 미치는 영향을 조사하였다. 기존의 제안식은 변위일정 법칙을 따라 일정주기 이상에서 비탄성 변위비를 과대평가하게 된다. 또한 기존식은 5%이상의 감쇠비에 대하여만 제안되었다. 본 연구는 후탄성기울기, 감쇠비 20% 이하의 이선형 시스템의 비탄성 변위비의 평균과 편차를 제안하였고 범용적으로 사용할 수 있음을 보였다. 제안식을 사용하여 비탄성 변위비의 확률적 분포를 계산하여 구조물의 성능기반설계에 이용할 수 있다.

• 한국지진공학회논문집
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• 제26권1호
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• pp.31-38
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• 2022

Based on the nonlinear static analysis and the approximate seismic evaluation method adopted in "Guidelines for seismic performance evaluation for existing buildings, two methods to calculate strength demand for retrofitting individual structural walls in unreinforced masonry buildings are proposed." The displacement coefficient method to determine displacement demand from nonlinear static analysis results is used for the inverse calculation of overall strength demand required to reduce the displacement demand to a target value meeting the performance objective of the unreinforced masonry building to retrofit. A preliminary seismic evaluation method to screen out vulnerable buildings, of which detailed evaluation is necessary, is utilized to calculate overall strength demand without structural analysis based on the difference between the seismic demand and capacity. A system modification factor is introduced to the preliminary seismic evaluation method to reduce the strength demand considering inelastic deformation. The overall strength demand is distributed to the structural walls to retrofit based on the wall stiffness, including the remaining walls or otherwise. Four detached residential houses are modeled and analyzed using the nonlinear static and preliminary evaluation procedures to examine the proposed method.

• Steel and Composite Structures
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• 제13권1호
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• pp.1-13
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• 2012

In this study, a new structural bracing system named 'Hat Knee Bracing' (HKB) is presented. In this structural system, a special form of diagonal braces, which is connected to the knee elements instead of beam-column joints, is investigated. The diagonal elements provide lateral stiffness during moderate earthquakes. However the knee elements, which is a fuse-like component, is designed to have one plastic joint in the knee elements for dissipation of the energy caused by strong earthquake. First, a suitable shape for brace and knee elements is proposed through elastic studying of the system and several practical parameters are established. Afterward, by developing applicable and highly accurate models in Drain-2DX, the inelastic behavior of the system is carefully considered. In addition, with inelastic study of the new bracing system and comparison with the prevalent Knee Bracing Frame system (KBF model) in nonlinear static and dynamic analysis, the seismic behavior of the new bracing system is reasonably evaluated.