• Structural Engineering and Mechanics
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• 제84권2호
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• pp.155-165
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• 2022

The use of electricity and communication between electronic devices is increasing daily, which makes the stability of electrical power supply vital. Since the 1990s, large earthquakes have occurred frequently causing considerable direct damage to electrical power facilities as well as secondary damage, such as difficulty in restoring functions due to the interruption of electric power supply. Therefore, it is very important to establish measures to protect electrical power facilities, such as transformers and switchboards, from earthquakes. In this study, a 154 kV transformer whose service life had expired was installed on the base fabricated by simulating the field conditions and conducting the shaking table tests. The dynamic characteristics and seismic behavior of the 154 kV transformer were analyzed through the resonance frequency search test and seismic simulation test that considers the front, rear, left, and right directions. Since the purpose of this study is to analyze the acceleration amplification in the bushing due to the acceleration amplification, the experimental results were analyzed focusing on the acceleration response and the converted acceleration amplification ratio rather than the failure due to the displacement response of the transformer. The seismic force amplification at the transformer bushing was evaluated by simulating the characteristics of electrical power facilities in South Korea, and compared with the IEC TS 61463 acceleration amplification factor. Finally, the amplification factor at zero period acceleration (ZPA) modified for each return period was summarized. The results of this study can be used as data to define the amplification factor at ZPA of the transformer bushing, simulating the characteristics of electrical power facilities in Korea.

• Geomechanics and Engineering
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• 제36권2호
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• pp.157-166
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• 2024

Generally, the rubble mound installed on the slope embankment of the open-type wharf is designed based on the impact of wave force, with no consideration for the impact of seismic force. Therefore, in this study, dynamic centrifuge model test results were analyzed to examine the acceleration amplification of embankment reinforced with rubble mound under seismic conditions. The experimental results show that when rubble mounds were installed on the ground surface of the embankment, acceleration response of embankment decreased by approximately 22%, and imbalance in ground settlement decreased significantly from eight to two times. Furthermore, based on the experimental results, one-dimensional site response (1DSR) analyses were conducted. The analysis results indicated that reinforcing the embankment with rubble mound can decrease the peak ground acceleration (PGA) and short period response (below 0.6 seconds) of the ground surface by approximately 28%. However, no significant impact on the long period response (above 0.6 seconds) was observed. Additionally, in ground with lower relative density, a significant decrease in response and wide range of reduced periods were observed. Considering that the reduced short period range corresponds to the critical periods in the design response spectrum, reinforcing the loose ground with rubble mound can effectively decrease the acceleration response of the ground surface.

• Earthquakes and Structures
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• 제24권1호
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• pp.53-64
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• 2023

Earth fissures with several kilometers will inevitably approach or cross the metro line, significantly threatening the safety of the underground structure in the earth fissure site. However, the influence of the earth fissure site's amplification effect on the metro station's dynamic response is still unclear. A representative earth fissure in Xi'an was taken as an example to establish a numerical model of a metro station in the earth fissure site. The dynamic response characteristics of the metro stations at different distances from the earth fissure under various seismic waves were calculated. The results show that the existence of the earth fissure significantly amplifies the dynamic response of the nearby underground structures. The responses of the axial force, shear force, bending moment, normal stress, horizontal displacement, inter-story drift, and relative slip of the metro station were all amplified within a specific influence range. The amplification effect increases with the seismic wave intensity. The amplification effect caused by the earth fissure has relatively weak impacts on the axial shear, shear force, bending movement, normal stress, and horizontal movement; slightly larger impacts on the inter-story drift and acceleration; and a significant impact on the relative slip. The influence ranges of the axial force and normal stress are approximately 20 m. The influence ranges of the acceleration and inter-story drift can reach 30 m. Therefore, the seismic fortification level of the underground structure in the earth fissure site needs to be improved.

• Structural Engineering and Mechanics
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• 제42권1호
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• pp.121-129
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• 2012

All contemporary seismic Codes have adopted smooth design acceleration response spectra, which have derived by statistical analysis of many elastic response spectra of natural accelerograms. The above smooth design spectra are characterized by two main branches, an horizontal branch that is 2.5 times higher than the peak ground acceleration, and a declining parabolic branch. According to Eurocode EN/1998, the period range of the horizontal, flat branch is extended from 0.1 s, for rock soils, up to 0.8 s for softer ones. However, from many natural recorded accelerograms of important earthquakes, the real spectral amplification factor appears to be much higher than 2.5 and this means that the spectrum leads to an unsafe seismic design of the structures. This point is an issue open to question and it is the object of the present study. In the present paper, the spectral amplification factor of the smooth design acceleration spectra is re-calculated on the grounds of a known "reliability index" for a desired probability of exceedance. As a pilot scheme, the seismic area of Greece is chosen, as it is the most seismically hazardous area in Europe. The accelerograms of the 82 most important earthquakes, which have occurred in Greece during the last 38 years, are used. The soil categories are taken into account according to EN/1998. The results that have been concluded from these data are compared with the results obtained from other strong earthquakes reported in the World literature.

• Geomechanics and Engineering
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• 제9권2호
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• pp.125-144
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• 2015

This paper presents the probabilistic seismic microzonation of densely populated Kolkata city, situated on the world's largest delta island with very soft alluvial soil deposit. At first probabilistic seismic hazard analysis of Kolkata city was carried out at bedrock level and then ground motion amplification due to sedimentary deposit was computed using one dimensional (1D) wave propagation analysis SHAKE2000. Different maps like fundamental frequency, amplification at fundamental frequency, peak ground acceleration (PGA), peak ground velocity (PGV), peak ground displacement (PGD), maximum response spectral acceleration at different time period bands are developed for variety of end users, structural and geotechnical engineers, land use planners, emergency managers and awareness of general public. The probabilistically predicted PGA at bedrock level is 0.12 g for 50% exceedance in 50 years and maximum PGA at surface level it varies from 0.095 g to 0.18 g for same probability of exceedance. The scenario of simulated ground motion revealed that Kolkata city is very much prone to damage during earthquake.

• 한국전산구조공학회논문집
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• 제33권3호
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• pp.159-169
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• 2020

변전소 구조물 내부에 설치되는 전력설비의 내진설계 시 사용되는 변수인 가속도 증폭계수는 미국, 일본과 국내의 변전소 내진설계기준에서 제시되어 있다. 국내 설계기준에 제시된 가속도 증폭계수는 미국, 일본의 설계기준에서 제시된 계수와는 달리 변전소 구조물의 층수가 4층 이상일 경우에는 동적해석을 수행하여 가속도 증폭계수를 구하게 되어 있다. 국내의 변전소 구조물은 대부분 층수가 4~5층이므로 기존의 가속도 증폭계수는 실제 변전소 구조물에 적용하기에 미흡한 상황이다. 국내 변전소 구조물 형식에 적합한 가속도 증폭계수를 제시하기 위하여 대표적인 7가지 구조형식의 변전소 구조물에 대하여 가속도 증폭계수를 평가하였다. 가속도증폭계수는 변전소 구조물에 대하여 원거리 지진과 근거리 지진을 사용하여 내부-구조물 응답스펙트럼을 작성하여 이로부터 평가하였다. 미국, 일본 전력설비 내진설계 기준에 따른 각각의 가속도 증폭계수 α_J, α_A는 근거리 및 원거리 지진을 사용한 동적 해석으로 구한 가속도 증폭계수에 비하여 다소 과대평가하는 경향이 있다.

• 한국지진공학회논문집
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• 제24권3호
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• pp.123-128
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• 2020

Analysis of the 2016 Gyeongju earthquake and the 2017 Pohang earthquake showed the characteristics of a typical high-frequency earthquake with many high-frequency components, short time strong motion duration, and large peak ground acceleration relative to the magnitude of the earthquake. Domestic nuclear power plants were designed and evaluated based on NRC's Regulatory Guide 1.60 design response spectrum, which had a great deal of energy in the low-frequency range. Therefore, nuclear power plants should carry out seismic verification and seismic performance evaluation of systems, structures, and components by reflecting the domestic characteristics of earthquakes. In this study, high-frequency amplification factors that can be used for seismic verification and seismic performance evaluation of nuclear power plant systems, structures, and equipment were analyzed. In order to analyze the high-frequency amplification factor, five sets of seismic time history were generated, which were matched with the uniform hazard response spectrum to reflect the characteristics of domestic earthquake motion. The nuclear power plant was subjected to seismic analysis for the construction of the Korean standard nuclear power plant, OPR1000, which is a reactor building, an auxiliary building assembly, a component cooling water heat exchanger building, and an essential service water building. Based on the results of the seismic analysis, a high-frequency amplification factor was derived upon the calculation of the floor response spectrum of the important locations of nuclear power plants. The high-frequency amplification factor can be effectively used for the seismic verification and seismic performance evaluation of electric equipment which are sensitive to high-frequency earthquakes.

• 한국지반공학회논문집
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• 제36권11호
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• pp.21-33
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• 2020

본 연구에서는 국내 내진설계기준 공통적용사항(MOIS, 2017)의 지반증폭계수를 활용하여 지표면 최대가속도를 산출하는 방법의 적절성을 검토하기 위해 포항지역 전역의 시추공을 대상으로 1차원 등가선형해석프로그램을 통해 지반응답해석을 수행하였다. 지반응답해석을 위한 지진파는 내진설계기준 공통적용사항에 따라 지진 재현주기 500년, 1000년, 2400년의 표준설계응답스펙트럼에 맞추었고, 지반데이터는 국토지반정보 포털시스템을 활용하여 확보하였다. 그 결과 내진설계기준 공통적용사항에서 제시하는 응답스펙트럼과 지반응답해석에서 얻어진 응답스펙트럼은 지반분류에 상관없이 대략적으로 일치하는 것을 알 수 있었다. 하지만, 증폭계수를 활용하여 지표면최대가속도를 산출할 경우 지반응답해석에서 얻어진 결과와 상당한 차이를 나타내는 것을 알 수 있었다.

• 한국지진공학회논문집
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• 제17권6호
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• pp.279-291
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• 2013

The seismic damage of non-structural components, such as communication facilities, causes direct economic losses as well as indirect losses which result from social chaos occurring with downtime of communication and financial management network systems. The current Korean seismic code, KBC2009, prescribes the design criteria and requirements of non-structural components based on their elastic response. However, it is difficult for KBC to reflect the dynamic characteristics of structures where non-structural components exist. In this study, both linear and nonlinear time history analyses of structures with various analysis parameters were carried out and floor acceleration spectra obtained from analyses were compared with both ground acceleration spectra used for input records of the analyses and the design floor acceleration spectrum proposed by National Radio Research Agency. Also, this study investigates to find out the influence of structural dynamic characteristics on the floor acceleration spectra. The analysis results show that the acceleration amplification is observed due to the resonance phenomenon and such amplification increases with the increase of building heights and with the decrease of structure's energy dissipation capacities.

• 한국지반신소재학회논문집
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• 제19권4호
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• pp.51-63
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• 2020

본 연구에서는 지진가속도 계측기의 계측 데이터를 사용하여 저수지의 동적해석방법에 대한 모형 검정 및 저수지 높이에 따른 지진가속도 증폭 특성을 분석하였다. 모형을 검정하기 위해 댐 기초의 계측 데이터를 입력 데이터로 사용하였고 해석 결과를 댐 상부의 계측 데이터와 비교한 결과 수치해석을 이용해 출력된 지진파와 계측 지진파의 최댓값과 그 파형이 비슷하게 나타났고 지진가속도 증폭 특성의 경우 지진가속도 증폭비는 저수지의 높이와 지진의 크기에 비례하는 것으로 나타났다. 본 연구를 통해 저수지에 설치된 가속도계에서 얻은 계측 데이터를 활용하여 반복 탄소성 구성식을 이용한 동적해석방법은 지진파 특성 분석이 적절하게 수행될 수 있는 기법임을 확인하였고 향후 이러한 기법을 적용해 저수지의 지진가속도 계측기의 활용도를 제고할 수 있을 것으로 판단된다.