• 한국환경복원기술학회지
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• 제10권4호
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• pp.31-40
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• 2007

Recently, the scale in the field of reinforced soil retaining wall has been grown up like tiered reinforced soil retaining wall. However, there have been increasing number of collapse accidents and large scale of collapse. The design manual adopted in the construction fields have been inconsistent in tiered reinforced soil retaining wall. Therefore, this study performed finite element analysis on 90 cases and analyzed characteristic behavior of lower wall which was one of the effect factors on the stability of tiered reinforced soil retaining wall. The facing displacement of each walls and the behavior of the whole ground were interpreted by the numerical analysis depending on the lower offset distance by the upper wall as well as the upper offset distance by the surcharge load. The results showed that the behavior of tiered reinforced soil retaining wall was differed by condition of surcharge load and each offset distance was found to be important factor.

• Earthquakes and Structures
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• 제14권4호
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• pp.349-360
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• 2018

Reinforced concrete (RC) moment frames supported on two ground levels have been widely constructed in mountainous areas with medium to high seismicity in China. In order to investigate the seismic collapse behavior and risk, a scaled frame model was tested under constant axial load and reversed cyclic lateral load. Test results show that the failure can be induced by the development of story yielding at the first story above the upper ground. The strong column and weak beam mechanism can be well realized at stories below the upper ground. Numerical analysis model was developed and calibrated with the test results. Three pairs of six case study buildings considering various structural configurations were designed and analyzed, showing similar dynamic characteristics between frames on two ground levels and flat ground of each pair. Incremental dynamic analyses (IDA) were then conducted to obtain the seismic collapse fragility curves and collapse margin ratios of nine analysis cases designated based on the case study buildings, considering amplification of earthquake effect and strengthening measures. Analysis results indicate that the seismic collapse safety is mainly determined by the stories above the upper ground. The most probable collapse mechanism may be induced by the story yielding of the bottom story on the upper ground level. The use of tie beam and column strengthening can effectively enhance the seismic collapse safety of frames on two ground levels.

• Earthquakes and Structures
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• 제11권3호
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• pp.445-459
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• 2016

Quantitative estimation of seismic response of various structural systems at the collapse limit state is one of the most significant objectives in Performance-Based Earthquake Engineering (PBEE). Assessing the effects of uncertainties, due to variability in ground motion characteristics and random nature of earthquakes, on nonlinear structural response is a pivotal issue regarding collapse safety prediction. Incremental Dynamic Analysis (IDA) and fragility curves are utilized to estimate demand parameters and seismic performance levels of structures. Since producing these curves based on a large number of nonlinear dynamic analyses would be time-consuming, selection of appropriate earthquake ground motion records resulting in reliable responses with sufficient accuracy seems to be quite essential. The aim of this research study is to propose a methodology to assess the seismic behavior of reinforced concrete frames at collapse limit state via accurate estimation of seismic fragility curves for different Engineering Demand Parameters (EDPs) by using a limited number of ground motion records. Research results demonstrate that accurate estimating of structural collapse capacity is feasible through applying the proposed method offering an appropriate suite of limited ground motion records.

• 한국안전학회지
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• 제20권1호
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• pp.55-61
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• 2005

The purpose of this study is to investigate the effect of circumferential location of local wall thinning defect on the collapse behavior of an elbow. Thus, the present study conducts three-dimensional finite element analysis on the 90-degree elbow containing a local wall thinning at intrados, crown and extrados of bend region and evaluates the collapse moment of wall thinned elbow under various thinning shapes and loading conditions. Combined internal pressure and bending moment are considered as an applied load. The internal pressure of $0\~20MPa$ and both closing and opening mode bending are employed. The results of analysis show that the reduction in collapse moment of the elbow by local wall thinning is more significant for a defect locating at crown than for a defect locating at intrados or at extrados. Also, the effect of internal pressure on the collapse moment of wall thinned elbow depends on the circumferential location of thinning defect and applied bending mode.

• 전산구조공학
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• 제23권1호
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• pp.41-48
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• 2010

• 대한기계학회논문집A
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• 제28권4호
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• pp.402-409
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• 2004

The purpose of this study is to investigate the effect of local wall thinning on the collapse of elbow subjected to internal pressure and bending moment. Thus, the nonlinear three-dimensional finite element analyses were performed to obtain the collapse moment of elbow containing various wall thinning defects located at intrados and extrados under two loading modes (closing and opening modes) with internal pressure. From the results of analysis, the effect of wall thinning defect on the global moment-rotation behavior of elbow was discussed, and the dependence of collapse moment of elbow on wall thinning depth, length, and circumferential angle was investigated under different loading mode and defect location.

• 한국지반환경공학회 논문집
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• 제17권4호
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• pp.39-46
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• 2016

터널구조물의 안정성 최종평가는 굴착완료 후 현장계측을 수행하여 계측값의 수렴 여부를 통해 판단하는 것이 일반적 평가 기준이다. 본 연구에서는 굴착하는 터널 주변 지반조건이 불량하여 터널 안정성 확보를 위한 보강을 적용한 후 국부적으로 보강구간에서 추가적인 붕락 또는 과다변위가 발생한 터널현장시공 사례의 해석적 방법과 상관성을 분석하였다. 추가 붕락터널에서 붕락유형을 조사해 보면 대부분 천단부 붕락이 발생하고 붕락된 구간에 대한 지질적인 조건을 분석해보면 천단부에서 지표부 인근까지 연장되어 존재하는 단층파쇄대가 존재하는 경우와 상관성이 있는 것으로 분석되었다. 이와같이 단층파쇄대와 같은 지반조건이 터널 천단부에서 지표부 인근까지 연장성을 가지는 경우에는 기존 수치해석적 방법으로 예측한 거동보다 더 큰 거동을 하는 것으로 분석되었다.

• Steel and Composite Structures
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• 제19권5호
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• pp.1237-1258
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• 2015

This paper proposes a simple inelastic analysis approach to efficiently map out the complete nonlinear post-collapse (strain-softening) response and the maximum load capacity of axially loaded concrete encased steel composite columns (stub and slender). The scheme simultaneously incorporates the influences of difficult instabilizing phenomena such as concrete confinement, initial geometric imperfection, geometric nonlinearity, buckling of reinforcement bars and local buckling of structural steel, on the overall behavior of the composite columns. The proposed numerical method adopts fiber element discretization and an iterative M${\ddot{u}}$ller's algorithm with an additional adaptive technique that robustly yields solution convergence. The accuracy of the proposed analysis scheme is validated through comparisons with various available experimental benchmarks. Finally, a parametric study of various key parameters on the overall behaviors of the composite columns is conducted.

• 한국지반환경공학회 논문집
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• 제16권12호
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• pp.37-43
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• 2015

터널구조물은 굴착 주변 지반의 강도를 활용하는 구조물로서 지반특성이 가장 중요하다. 단층파쇄대와 같은 취약한 지반 조건이 터널 굴착 구간에 존재하는 경우, 특히 단층파쇄대와 지하수 용출이 동시에 발생하는 조건에서는 터널 굴착 중 과다변위 또는 붕락 등이 자주 발생한다. 이러한 단층파쇄대는 터널 굴착 중 변위 및 붕락의 방향을 결정해주는 중요한 요인이 된다. 단층파쇄대의 규모 및 지표부와의 방향성에 따라 터널 거동 특성이 결정되고 이와 더불어 지하수 용출이 발생되는 경우에는 터널 굴착 중 발생되는 변위 및 붕락 특성이 시간 의존적인 거동을 하게 되는 결정적인 요인이 된다. 단층파쇄대 구간에서 지하수 용출을 해석적인 방법으로 예측하거나 지하수 용출과 단층파쇄대의 상호거동을 분석하였을 경우에 정확하게 예측을 하기가 어렵다. 따라서 단층파쇄대와 지하수가 동시에 발생하는 구간에서는 해석적인 분석방법으로는 한계가 있으므로 실제 시공사례를 분석하여 거동을 종합적으로 예측하는 것이 필요하다. 본 연구에서는 단층파쇄대의 위치에 따른 실제 터널 거동 특성을 분석하였다.

• 터널과지하공간
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• 제25권1호
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• pp.68-75
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• 2015

암반에는 단층 절리 층리 균열 편리 벽개 등 불연속면이 포함되어 있다. 따라서, 불연속면을 포함한 암반의 역학적 거동은 연속체와는 다르게 불연속면의 역학적 거동에 좌우된다. 본 연구에서는 불연속면을 고려한 암반의 안정변형해석기법을 제안하고, 암반 붕괴재난현장에 적용했다. 암반 불연속면을 고려하여 평사투영법에 의한 안정해석과 개별절리요소를 포함한 유한요소법에 의한 변형해석 프로그램을 개발하여, 실제 암반 붕괴 재난현장 지역에서의 해석결과와 비교 및 검토를 하였다. 암반 현장에 적용하여 결과를 비교 검토함으로써, 암반의 파괴 거동 해석에 있어서 개발한 불연속면을 고려한 암반의 안정변형해석법의 적용성에 대한 검증을 하였다.