• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1999년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall
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• pp.91-98
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• 1999

In this study a modified ground strain model is developed for an equivalent earthquake load and is applied to the seismic analysis of buried pipelines, The ground strain can be obtained using the ratio of a maximum ground velocity to a wave propagation velocity. To reflect soil conditions and seismic characteristics the wave propagation velocity is evaluated by a proposed dispersion curve based on wave energy distribution. In order to verify the procedures the observed earthquake data and the results of this study are compared. For the application of an equivalent earthquake load to the seismic analysis the buried pipelines are modeled using the beam theory. the results of the analyses are compared with those of a dynamic analysis code and those obtained from the response displacement method. Finally various parametric studies considering different soil conditions and seismic loads are examined.

• Steel and Composite Structures
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• 제41권6호
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• pp.831-850
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• 2021

Surface subsidence caused by mining subsidence has an impact on neighboring structures and utilities. In other words, subsurface voids created by mining or tunneling activities induce soil movement, exposing buildings to physical and/or functional destruction. Soil-structure is evaluated employing probability distribution laws to account for their uncertainty and complexity to estimate structural vulnerability. In this study, to investigate the displacement field and surface settlement profile caused by mining subsidence, on the basis of a Winklersoil model, analytical equations for the moment-rotation response ofsoil during mining induced ground movements are developed. To define the full static moment-rotation response, an equation for the uplift-yield state is constructed and integrated with equations for the uplift- and yield-only conditions. The constructed model's findings reveal that the inverse of the factor of safety (x) has a considerable influence on the moment-rotation curve. The maximal moment-rotation response of the footing is defined by X = 0:6. Despite the use of Winkler model, the computed moment-rotation response results derived from the literature were analyzed through the ELM-SVM hybrid of Extreme Learning Machine (ELM) and Support Vector Machine (SVM). Also, Monte Carlo simulations are used to apply continuous random parameters to assess the transmission of ground motions to structures. Following the findings of RMSE and R2, the results show that the choice of probabilistic laws of input parameters has a substantial impact on the outcome of analysis performed.

• 한국지진공학회논문집
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• 제9권6호
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• pp.41-52
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• 2005

서울시 모델 구역의 건축물을 대상으로 가상 시나리오 지진에 의한 피해를 추정하였다. 다양한 주거 및 구조 특성을 대표할 수 있고 지반 증폭 효과를 고려할 수 있는 지역을 모델 구역으로 선정하였다. 모델 구역 내 건축물은 구조 형식에 따라 11 종류로 분류하였으며 HAZUS에서 제시한 값을 사용하여 역량 곡선(capacity curve)과 취약도 곡선(fragility curve)을 생성하였다. 가상 시나리오 지진의 지반 운동은 인공 지진 운동 생성 방법을 사용하여 생성하였으며 모델 구역을 표토층 두께에 따라 3개의 구역으로 나누고 지반응답해석을 수행하였다. 건축물의 피해 확률은 역량 스펙트럼 방법과 취약도 곡선을 사용하여 계산하였다. 최종적으로 GIS 데이터베이스를 활용하여 모델 구역 내 건축물의 전반적 피해 정도를 추정하였다.

• 한국지진공학회논문집
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• 제20권6호
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• pp.413-424
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• 2016

The vertical design spectrum for Korea, which is known to belong to an intra-plate region, is developed from the ground motion records of the earthquakes occurred in Korea and overseas intra-plate regions. From the statistical analysis of the vertical response spectra, a mean plus one standard deviation spectrum in lognormal distribution is obtained. Regression analysis is performed on this curve to determine the shape of spectrum including transition periods. The developed design spectrum is valid for the estimation both spectral acceleration and displacement. The ratio of vertical to horizontal response spectrum for each record is calculated. Statistical analysis of the ratios rendered the vertical to horizontal ratio (V/H ratio). Subsequently the ratio between the peak vertical ground acceleration to the horizontal one is obtained.

• Earthquakes and Structures
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• 제16권6호
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• pp.705-714
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• 2019

Seismic assessment of underground structures is one of the challenging problems in engineering design. This is because there are usually many sources of uncertainties in rocks and probable earthquake characteristics. Therefore, for decreasing of the uncertainties, seismic response of underground structures should be evaluated by sufficient number of earthquake records which is scarcely possible in common seismic assessment of underground structures. In the present study, a practical risk-based approach was performed for seismic risk assessment of an unsupported tunnel. For this purpose, Incremental Dynamic Analysis (IDA) was used to evaluate the seismic response of a tunnel in south-west railway of Iran and different analyses were conducted using 15 real records of earthquakes which were chosen from the PEER ground motion database. All of the selected records were scaled to different intensity levels (PGA=0.1-1.7 g) and applied to the numerical models. Based on the numerical modeling results, seismic fragility curves of the tunnel under study were derived from the IDA curves. In the next, seismic risk curve of the tunnel were determined by convolving the hazard and fragility curves. On the basis of the tunnel fragility curves, an earthquake with PGA equal to 0.35 g may lead to severe damage or collapse of the tunnel with only 3% probability and the probability of moderate damage to the tunnel is 12%.

• Nuclear Engineering and Technology
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• 제52권1호
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• pp.192-205
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• 2020

Seismic design practices and seismic response analyses of civil structures and nuclear power plants (NPPs) have conventionally used the peak ground acceleration (PGA) or spectral acceleration (S_a) as an intensity measure (IM) of an earthquake. However, there are many other earthquake IMs that were proposed by various researchers. The aim of this study is to investigate the correlation between seismic responses of NPP components and 23 earthquake IMs and identify the best IMs for correlating with damage of NPP structures. Particularly, low- and high-frequency ground motion records are separately accounted in correlation analyses. An advanced power reactor NPP in Korea, APR1400, is selected for numerical analyses where containment and auxiliary buildings are modeled using SAP2000. Floor displacements and accelerations are monitored for the non- and base-isolated NPP structures while shear deformations of the base isolator are additionally monitored for the base-isolated NPP. A series of Pearson's correlation coefficients are calculated to recognize the correlation between each of the 23 earthquake IMs and responses of NPP structures. The numerical results demonstrate that there is a significant difference in the correlation between earthquake IMs and seismic responses of non-isolated NPP structures considering low- and high-frequency ground motion groups. Meanwhile, a trivial discrepancy of the correlation is observed in the case of the base-isolated NPP subjected to the two groups of ground motions. Moreover, a selection of PGA or S_a for seismic response analyses of NPP structures in the high-frequency seismic regions may not be the best option. Additionally, a set of fragility curves are thereafter developed for the base-isolated NPP based on the shear deformation of lead rubber bearing (LRB) with respect to the strongly correlated IMs. The results reveal that the probability of damage to the structure is higher for low-frequency earthquakes compared with that of high-frequency ground motions.

• 한국지반공학회논문집
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• 제32권11호
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• pp.31-42
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• 2016

지진에 대한 사면안정 해석은 지진에 의한 관성력을 정적하중으로 고려하는 유사정적해석을 널리 사용하고 있다. 사면과 같은 지반 구조물은 지반정수의 불확실성이 포함되어 있어 확률론적 해석을 이용하여 지반정수의 불확실성을 고려해야 한다. 본 연구에서는 지반의 불확실성을 고려한 확률론적 사면안정해석을 수행하였으며, 구조물이 임의 수준의 지반 운동을 받을 때 파괴상태에 도달하는 확률을 그래프로 나타낸 취약도 곡선을 작성하였다. 유사정적해석으로 확률론적 사면안정해석을 수행하기 위해 Monte Carlo Simulation(MCS)을 시행하였다. MCS의 소요 시간을 단축하기 위하여 인공신경망 기반의 응답면 기법을 이용해 파괴확률을 산출하여 수평지진계수별 취약도 곡선을 작성하는 방법을 제시하였다. 인공신경망을 이용하여 작성한 취약도 곡선을 MCS의 결과와 비교해 본 결과 상당한 시간 절약에 비해 유사한 결과를 얻을 수 있었다.

• Structural Engineering and Mechanics
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• 제59권3호
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• pp.455-473
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• 2016

Methods for the seismic demands evaluation of structures require iterative procedures. Many studies dealt with the development of different inelastic spectra with the aim to simplify the evaluation of inelastic deformations and performance of structures. Recently, the concept of inelastic spectra has been adopted in the global scheme of the Performance-Based Seismic Design (PBSD) through Capacity-Spectrum Method (CSM). For instance, the Modal Pushover Analysis (MPA) has been proved to provide accurate results for inelastic buildings to a similar degree of accuracy than the Response Spectrum Analysis (RSA) in estimating peak response for elastic buildings. In this paper, a simplified nonlinear procedure for evaluation of the seismic demand of structures is proposed with its applicability to multi-degree-of-freedom (MDOF) systems. The basic concept is to write the equation of motion of (MDOF) system into series of normal modes based on an inelastic modal decomposition in terms of ductility factor. The accuracy of the proposed procedure is verified against the Nonlinear Time History Analysis (NL-THA) results and Uncoupled Modal Response History Analysis (UMRHA) of a 9-story steel building subjected to El-Centro 1940 (N/S) as a first application. The comparison shows that the new theoretical approach is capable to provide accurate peak response with those obtained when using the NL-THA analysis. After that, a simplified nonlinear spectral analysis is proposed and illustrated by examples in order to describe inelastic response spectra and to relate it to the capacity curve (Pushover curve) by a new parameter of control, called normalized yield strength coefficient (${\eta}$). In the second application, the proposed procedure is verified against the NL-THA analysis results of two buildings for 80 selected real ground motions.

• 한국지반공학회논문집
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• 제18권3호
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• pp.126-126
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• 2002

지진에 의한 지반거동 및 지반-구조물 상호작용 등 지반동역학적 문제분석을 위해서는 정확한 동적 토질전단탄성계수의 획득이 필수적이다. 본 연구에서는 기존의 자료를 조사분석하여 어떤 변형율에서도 활용할 수 있는 사질토 전단탄성계수 감소곡선을 위한 경험식을 제안하였다. 비소성 토질의 전단탄성계수 감소곡선의 위치와 모양은 평균유효구속압에 주로 영향을 받으므로 본 연구에서는 이 영향요소 및 최대전단탄성계수를 이용하여 변형을 증가에 의한 전단탄성계수 감소를 산정할 수 있는 방정식을 형성하였다. 최대전단탄성계수가 측정되면 제안된 식을 이용하여 특정 변형을 및 구속압에서 감소된 전단탄성계수를 산출할 수 있을 것이다.

• 한국지반공학회논문집
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• 제18권3호
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• pp.127-138
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• 2002

지진에 의한 지반거동 및 지반-구조물 상호작용 등 지반동역학적 문제분석을 위해서는 정확한 동적 토질전단탄성계수의 획득이 필수적이다. 본 연구에서는 기존의 자료를 조사분석하여 어떤 변형율에서도 활용할 수 있는 사질토 전단탄성계수 감소곡선을 위한 경험식을 제안하였다. 비소성 토질의 전단탄성계수 감소곡선의 위치와 모양은 평균유효구속압에 주로 영향을 받으므로 본 연구에서는 이 영향요소 및 최대전단탄성계수를 이용하여 변형을 증가에 의한 전단탄성계수 감소를 산정할 수 있는 방정식을 형성하였다. 최대전단탄성계수가 측정되면 제안된 식을 이용하여 특정 변형을 및 구속압에서 감소된 전단탄성계수를 산출할 수 있을 것이다.