• Title, Summary, Keyword: 지진응답 수정계수

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Development of Novel Method of Seismic Slope Stability Analysis (신(新) 유사정적 사면안정해석 기법 개발)

  • Yun, Seung;Park, Duhee;Lee, Seungho;Hwang, Youngchul
    • Journal of the Korean Geoenvironmental Society
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    • v.10 no.1
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    • pp.49-54
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    • 2009
  • The seismic slope stability is most often evaluated by the pseudo-static limit analysis, in which the earthquake loading is simplified as static inertial loads acting in horizontal and/or vertical directions. The transient loading is represented by constant acceleration via the pseudostatic coefficients. The result of a pseudostatic analysis is governed by the selection of the value of the pseudostatic coefficient. However, selection of the value is very difficult and often done in an ad hoc manner without a sound physical reasoning. In addition, the maximum acceleration is commonly estimated from the design guideline, which cannot accurately estimate the dynamic response of a slope. There is a need to perform a 2D dynamic analysis to properly define the dynamic response characteristics. This paper develops a new hybrid pseudostatic method that links the modified one-dimensional seismic site response analysis and the pseudostatic algorithm. The modified site response analysis adjusts the density of the layers to simulate the change in mass and weight of the layers of the slope with depth. Multiple analyses were performed at various locations within the slope to estimate the change in seismic response of the slope. The calculated peak acceleration profiles with depth from the developed procedure were compared to those by the two-dimensional analyses. Comparisons show that the two methods result in remarkable match. The calculated profiles are used to perform pseudostatic analysis. The results show that use of peak or a fraction of acceleration at the surface can seriously underestimate or overestimate the factor of safety, and that the proposed procedure significantly enhances the reliability of a standard procedure.

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Seismic Capacity according to Structural System of High-rise Apartment (고층 아파트 구조시스템에 따른 내진성능 분석)

  • Lee, Minhee;Cho, So-Hoon;Kim, Jong-Ho;Kim, Hyung-Do
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.32 no.3
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    • pp.149-154
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    • 2019
  • The structural system of domestic high-rise apartments can be divided into two parts; the core wall system, which is composed of walls concentrated in the center and the shear wall system, which comprises a great number of walls distributed in the plan. In order to analyze the lateral behavior of each system, buildings with typical domestic high-rise apartment plans were selected and nonlinear static analysis was performed to investigate the their collapse mechanism. From the force-displacement relation derived from nonlinear static analysis, response modification factor was evaluated by calculating the overstrengh and ductility factor, which are important in the seismic response. The ductility of core wall system is small, but as it is governed by wind load, its overstrength is greatly estimated, and its response modification factor is calculated by the overstrengh factor. Due to a large number of walls, shear wall system has a large ductility, making the response modification factor considerably large.

Equivalent Linear Stiffness Matrix of Pile Foundation for the Seismic Response Analysis of Bridges (교량의 지진응답해석을 위한 말뚝기초의 등가 선형 강도행렬)

  • 박형기;조양희
    • Journal of the Earthquake Engineering Society of Korea
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    • v.5 no.3
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    • pp.1-8
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    • 2001
  • Seismic design forces for bridge components may be determined by modifying elastic member forces of design earthquakes using appropriate response modification factors according to the national design code of bridges Modeling technique of pile foundation system is one of the important parameters which greatly affects the results in the process of the elastic seismic analysis of a bridge system with pile foundation. In this paper, a approximate and simplified modeling technique of a pile foundation system for the practical purposes is presented. The modeling technique is based on the stiffnesses of pile foundation during earthquake. The horizontal stiffnesses are determined from the resistance-deflection curves derived from the results of dynamic field tests using cyclic loads and the vertical stiffness includes the effects of the end bearing capacities and side friction of piles as well as the pile compliances under the expected vertical load level. The applicability of the proposed technique has been validated through the some example bridge analyses.

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Energy Dissipation Demand of Braces Using Non-linear Dynamic Analyses of X-Braced Frame (비선형 동적 해석을 통한 X형 가새골조 내 가새 부재의 에너지 소산)

  • Lee, Kangmin
    • Journal of Korean Society of Steel Construction
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    • v.15 no.4
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    • pp.379-388
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    • 2003
  • The response of single story buildings and other case studies were investigated to observe trends and develop a better understanding of the impact of some design parameters on the seismic response of Concentrically Braced Frames (CBF). While many parameters are known to influence the behavior of braced frames, the focus of this study was mostly on quantifying energy dissipation in compression and its effectiveness on seismic performance. Based on dynamic analyses of single story braced frame and case studies, a bracing member designed with bigger R and larger KL/r was found to result in lower normalized cumulative energy ratio in both cases.

Evaluation of the Strength Required in Current Seismic Design Code (현행 내진설계 규준의 수평강도 요구에 대한 평가)

  • 한상환;오영훈;이리형
    • Computational Structural Engineering
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    • v.10 no.4
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    • pp.281-290
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    • 1997
  • Current seismic design code is based on the assumption that the designed structures would be behaved inelastically during a severe earthquake ground motion. For this reason, seismic design forces calculated by seismic codes are much lower than the forces generated by design earthquakes which makes structures responding elastically. Present procedures for calculating seismic design forces are based on the use of elastic spectra reduced by a strength reduction factors known as "response modificaion factor". Because these factors were determined empirically, it is difficult to know how much inelastic behaviors of the structures exhibit. In this study, lateral strength required to maintain target ductility ratio was first calculated from nonlinear dynamic analysis of the single degree of freedom system. At the following step, base shear foeces specified in seismic design code compare with above results. If the base shear force required to maintain target ductility ratio was higher than the code specified one, the lack of required strength should be filled by overstrength and/or redundancy. Therefore, overstrength of moment resisting frame structure will be estimated from the results of push-over analysis.

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비 격리교량의 연성도를 목표로 하는 지진격리교량의 응답수정계수

  • 고현무
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.432-439
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    • 2000
  • According as ground acceleration becomes to exceed gravity acceleration recently, design is impossible or economical efficiency is poor in existing seismic design method. So increase of seismic isolated bridges is currently in progress. However, because base isolation design method is developed in high seismic regions. it may not be compatible in Korea. Therefore, this research has objective to evaluate ductility of pier and response modification factor according to the ductility of pier in seismic isolated bridges and to adapt to seismic characteristics in Korea. For this purpose, nonlinear analysis is accomplished with so many time histories derived from spectral density function compatible with response spectrum described in the design code and base isolation system modeled linear system, bi-linear system, and friction system. Through application of the proposed method, we had result that it may be compatible that response modification factor for the seismic isolated bridges is smaller than half of that for the conventional bridges when natural period of structures exceeds proper level.

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Dynamic behavior of the bridge with seismic isolation bearing (내진 분리 베어링이 설치된 교량의 동적 거동)

  • 전귀현
    • Computational Structural Engineering
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    • v.7 no.1
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    • pp.83-90
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    • 1994
  • This study presents the nonlinear dynamic analysis method of the bridge with the seismic isolation bearing. Also the numerical analyses are performed for investigating the response characteristics of the bridge isolated with the lead-rubber bearing under the ground motions compatible to Korea bridge design response spectra. It is found that the pier design force can be considerably smaller than the one for the bridge with the fixed bearing. It is observed that the lead-rubber bearing has the great effectiveness for reducing the longitudinal seismic force in case of the bridges with low and medium periods. Therefore the seismic isolation bearing can be used instead of the fixed bearing for the economic and safe design of the bridge.

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A Study on the Ductility of Concrete-Filled Composite Columns under Cyclic Loading (반복하중을 받는 콘크리트충전 강합성 기둥의 연성에 관한 연구)

  • 송준엽;권영봉;김성곤
    • Journal of the Earthquake Engineering Society of Korea
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    • v.5 no.6
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    • pp.11-19
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    • 2001
  • A series of test on concrete-filled composite columns was preformed to evaluate structural performance under axial compression and cyclic lateral loading. It was presented that concrete-filled composite columns had high strength, high stiffness and large energy-absorption capacity on account of mutual confinement between the steel plate and filled-in concrete. A cross section analysis procedure developed to predict the moment-curvature relation of composite columns was proven to be on accurate and effective method. The ductility factor and the response modification factor were evaluated for the seismic design of concrete-filled composite columns. It was shown that concrete-filled composite columns could be used as a very efficient earthquake-resistant structural member.

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Seismic Performance Evaluation of RC Structure Strengthened by Steel Grid Shear Wall using Nonlinear Static Analysis (비탄성 정적해석을 이용한 격자강판 전단벽 보강 RC구조물의 내진성능평가)

  • Park, Jung Woo;Lee, Jae Uk;Park, Jin Young;Lee, Young Hak;Kim, Heecheul
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.26 no.6
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    • pp.455-462
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    • 2013
  • The effects of earthquakes can be devastating especially to existing structures that are not based on earthquake resistant design. This study proposes a steel grid shear wall that can provide a sufficient lateral resistance and can be used as a seismic retrofit method. The pushover analysis was performed on RC structure with and without the proposed steel grid shear wall. Obtain the performance point that the target structure for seismic loads applied to evaluate the response and performance levels. The capacity spectrum at performance point is nearly elastic range, so satisfied the performance objectives(LS level). And response modification factor(R factor) were calculated from the pushover analysis. The R factor approach is currently implemented to reflect inelastic ductile behavior of the structures and to reduce elastic spectral demands from earthquakes to the design level. The R factor increases from 2.17 to 3.25 was higher than the design criteria. As a result, according to reinforcement by steel grid shear wall, strength, stiffness, and ductility of the low-rise RC structure has been appropriately improved.

Deformation Based Seismic Design of Asymmetric Wall Structures (변형에 기초한 비대칭 벽식 주초의 내진설계)

  • 홍성걸;조봉호
    • Journal of the Earthquake Engineering Society of Korea
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    • v.6 no.1
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    • pp.43-53
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    • 2002
  • Current torsional provisions focus n restricting torsional effect of asymmetric wall structures by proportioning strength of wall based on the traditional assumption that stiffness and strength are independent. Recent studies have pointed out that stiffness of structural wall is dependent on the strength. This implies that actual stiffness of walls can be determined only after torsional design is finished and current torsional provisions may result in significant errors. To overcome this shortcoming, this paper proposes deformation based torsional design for asymmetric wall structures. Contrary to the current torsional provisions, deformation-based torsional design uses displacement and rotation angle as design parameters and calculates base shear for inelastic torsional response directly. Main purpose of deformation based torsional design is not to restrict torsional response but to ensure intended torsional mechanism according to the capacity design concept. Because displacement and rotation angle can be used as performance criteria indicating performance level of asymmetric structures, this method can be applied to the performance based seismic design effectively.