• Earthquakes and Structures
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• 제22권5호
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• pp.503-515
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• 2022

This paper presents the development of seismic fragility curves for a precast reinforced concrete bridge instrumented with a structural health monitoring (SHM) system. The bridge is located near an active seismic fault in the Dominican Republic (DR) and provides the only access to several local communities in the aftermath of a potential damaging earthquake; moreover, the sample bridge was designed with outdated building codes and uses structural detailing not adequate for structures in seismic regions. The bridge was instrumented with an SHM system to extract information about its state of structural integrity and estimate its seismic performance. The data obtained from the SHM system is integrated with structural models to develop a set of fragility curves to be used as a quantitative measure of the expected damage; the fragility curves provide an estimate of the probability that the structure will exceed different damage limit states as a function of an earthquake intensity measure. To obtain the fragility curves a digital twin of the bridge is developed combining a computational finite element model and the information extracted from the SHM system. The digital twin is used as a response prediction tool that minimizes modeling uncertainty, significantly improving the predicting capability of the model and the accuracy of the fragility curves. The digital twin was used to perform a nonlinear incremental dynamic analysis (IDA) with selected ground motions that are consistent with the seismic fault and site characteristics. The fragility curves show that for the maximum expected acceleration (with a 2% probability of exceedance in 50 years) the structure has a 62% probability of undergoing extensive damage. This is the first study presenting fragility curves for civil infrastructure in the DR and the proposed methodology can be extended to other structures to support disaster mitigation and post-disaster decision-making strategies.

• Structural Monitoring and Maintenance
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• 제10권1호
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• pp.87-105
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• 2023

Seismic regulations have been updated from time to time to accommodate an increase in seismic hazards. Comparison of seismic fragility of the existing bridges in Indonesia from different historical periods since the era before 1990 will be the basis for seismic assessment of the bridge stock in Indonesia, most of which are located in earthquake-prone areas, especially those built many years ago with outdated regulations. In this study, seismic fragility curves were developed using incremental non-linear time history analysis and more holistically according to the actual strength of concrete and steel material in Indonesia to determine the uncertainty factor of structural capacity, βc. From the research that has been carried out, based on the current seismic load in SNI 2833:2016/Seismic Map 2017 (7% probability of exceedance in 75 years), the performance level of the bridge in the era before SNI 2833:2016 was Operational-Life Safety whereas the performance level of the bridge designed with SNI 2833:2016 was Elastic - Operational. The potential for more severe damage occurs in greater earthquake intensity. Collapse condition occurs at As = F_PGA x PGA value of bridge Era I = 0.93 g; Era II = 1.03 g; Era III = 1.22 g; Era IV = 1.54 g. Furthermore, the fragility analysis was also developed with geometric variations in the same bridge class to see the effect of these variations on the fragility, which is the basis for making bridge risk maps in Indonesia.

• Geomechanics and Engineering
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• 제35권6호
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• pp.581-591
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• 2023

North Anatolian Fault Zone is tectonically active with recent earthquakes (Mw7.6 1999-Kocaeli and Mw7.2 1999-Düzce earthquakes) and it passes through Marmara region, which is highly industrialized, densely populated and economically important part of Turkey. Many power plants, located in Marmara region, are exposed to high seismic hazard. In this study, open source OpenQuake software has been used for the probabilistic earthquake hazard analysis of Marmara region and risk assessment for the specified energy facility. The SHARE project seismic zonation model has been used in the analysis with the regional sources, NGA GMPEs and site model logic trees. The earthquake hazard results have been compared with the former and existing earthquake resistant design regulations in Turkey, TSC 2007 and TBSCD 2018. In the scope of the study, the seismic hazard assessment for a typical natural gas combined cycle power plant located in Marmara region has been achieved. The seismic risk assessment has been accomplished for a typical control building located in the power plant using obtained seismic hazard results. The structural and non-structural fragility functions and a consequence model have been used in the seismic risk assessment. Based on the seismic hazard level with a 2% probability of exceedance in 50 years, considered for especially these type of critical structures, the ratios of structural and non-structural loss to the total building cost were obtained as 8.8% and 45.7%, respectively. The results of the study enable the practical seismic risk assessment of the critical facility located on different regions.

• 한국포장학회지
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• 제29권3호
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• pp.175-179
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• 2023

This paper analyzes the vibration characteristics within the cargo compartment of a three-wheeled cargo bike when used on both regular roads and dedicated bicycle lanes. When cargo is loaded into the cargo compartment of a cargo bike and driven on the road, the shocks and vibrations transmitted from the ground can potentially affect the transported goods and even lead to product damage. As the vibration characteristics applied to the cargo compartment may vary depending on the condition of the road, vibration sensors were attached to the cargo bike's cargo compartment for data collection during operation on different road types. According to KS T ISO 13355 standards, the cargo bike can withstand vibrations within the range of 10 Hz to 60 Hz when operating on both bicycle lanes and regular roads. However, it is observed that there are peaks exceeding the profile in the frequency range of 3-6 Hz. In the 70-200 Hz range, the profile is exceeded on both regular roads and bicycle lanes, with a tendency for higher exceedance on bicycle lanes. The Grms value within the frequency range of KS T ISO 13355 is 5.926 m/s² (0.604 Grms). When operating on bicycle lanes with cargo, the Peak envelope optimization PSD value is 6.553 Grms, while on bicycle lanes, it is 7.708 Grms, indicating a difference of at least tenfold.

• Annals of Occupational and Environmental Medicine
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• 제35권
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• pp.3.1-3.11
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• 2023

Background: Studies on the risk of mercury (Hg) in Korean fishery products focus primarily on total Hg levels as opposed to methylmercury (MeHg) levels. None of the few studies on MeHg in tuna investigated tuna from Japanese restaurants. Few have evaluated lead (Pb), cadmium (Cd) and arsenic (As) in tuna. Thus, this study aimed to conduct a risk assessment by evaluating heavy metal concentrations in tuna from Japanese restaurants. Methods: Thirty-one tuna samples were collected from Japanese restaurants in the Republic of Korea. They were classified according to region and species. The concentration of heavy metals in the samples was analyzed using the Ministry of Food and Drug Safety Food Code method. The rate of exceedance of maximum residue levels (MRLs) and the risk compared to the provisional tolerable weekly intake (PTWI) set by the Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives (%PTWI) were evaluated for risk assessment. Results: The mean of MeHg, Pb, Cd and As concentrations were 0.56 ± 1.47 mg/kg, 33.95 ± 3.74 ㎍/kg, 14.25 ± 2.19 ㎍/kg and 1.46 ± 1.89 mg/kg, respectively. No sample exceeded the MRLs of Pb and Cd, but 9.7% of the samples exceeded the MRL of MeHg. The %PTWIs of MeHg, Pb, Cd and As were 4.2037, 0.0162, 0.0244 and 1.1627, respectively. The %PTWI of MeHg by age group and sex was highest among men aged 19-29 years (10.6494), followed by men aged 30-49 years (7.2458) and women aged 19-29 years (4.8307). Conclusions: We found that 3 out of 31 samples exceeded the MRL of MeHg. The %PTWI of MeHg showed significant differences based on age and sex, and the value was likely to exceed a safe level depending on individuals' eating behaviors. Therefore, improved risk management for MeHg is required.

• Wind and Structures
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• 제39권2호
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• pp.85-100
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• 2024

In light of extreme value distribution probability, an improved prediction method of the Recurrence Period Wind Speed (RPWS) is constructed considering wind direction, with the Equivalent Independent Wind Direction Number (EIWDN) introduced as a parameter variable. Firstly, taking the RPWS prediction of Beijing city as an example, the traditional Cook method is used to predict the RPWS of each wind direction based on the measured wind speed data in Beijing area. On basis of the results, the empirical formulae to determine the parameter variables are fitted to construct an improved expression of the non-exceedance probability of the RPWS. In this process, the statistical model of the optimal threshold is established, and thus the independent wind speed samples exceeding the threshold are extracted and fitted to follow the Generalized Pareto Distribution (GPD) model for analysis. In addition, the Extreme Value Type I (EVT I) distribution model is used to predict and analyze the RPWS. To verify its wide applicability, the improved method is further used in cities like Jinan, Nanjing, Wuxi, Shanghai and Shenzhen to predict and analyze the RPWS of each wind direction, and the prediction results are compared against those gained via the traditional Cook method and the whole direction. Results show that the 50-year RPWS results predicted by the improved method are basically consistent with those predicted by the traditional method, and the RPWS prediction values of most wind directions are within the envelope range of the whole wind direction prediction value. Compared with the traditional method, the improved method can readily predict the RPWS under different return periods through empirical formulae, and avoid the repeated operation process and some assumptions in the traditional Cook method, and then improve the efficiency of prediction. In addition, the improved RPWS prediction results corresponding to the GPD model are slightly larger than those of the EVT I distribution model.

• 한국지반공학회논문집
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• 제35권11호
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• pp.111-119
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• 2019

지진에 대한 경각심이 높아지는 가운데 고속철도 시스템의 지진 취약성을 분석하는 것은 지진피해 사전대응분석을 위해 필수적이다. 고속철도를 이루는 구조물은 400km/s 정도까지 속도를 낼 수 있는 고속열차의 직진성을 유지하기 위해 주로 교량, 터널 등으로 구성되어 있다. 이러한 구조물의 지진에 대한 취약도는 각 구조물의 단면을 분석하여 해석적 또는 수치적 방법으로 구할 수도 있으나, 고속철도 전체 시스템을 이러한 방법으로 분석하기에는 그 대상이 넓어 많은 연구 노력이 필요하다. 본 연구에서는 이런 해석적 방법이 아닌 경험적 방법을 사용하여 고속철도 시스템 전체의 일반적인 지진 취약도 곡선을 개발하였다. 연구에 활용한 대상 지진 사례는 규모 6.6 2004년 니가타 지진으로, 이 지진은 진앙 인근 부근을 지나는 고속철도에 심각한 피해를 초래하였다. 본 연구에서는 고속철도에서의 계기진도 및 피해 사례를 수집하였고, 통계분석을 통해 각 피해 정도에 따른 피해 확률을 결정하였다. 그 후, 최대우도추정법을 사용하여 계기진도를 함수로 하는 초과피해 확률을 로그정규누적분포함수로 추정하였다. 이러한 취약도 곡선을 분석한 결과, 장주기 성분의 계기진도인 주기 3초의 응답스펙트럼(SA_T3.0)이 로그정규누적분포함수의 표준편차가 가장 작게 나타나고 오차의 표준편차 또한 작게 나타나 터널 및 교량 등 고속철도 시스템의 피해 확률을 추정하는데 가장 적합한 계기진도로 판단되었다. 이는 장주기 성분의 지진파가 터널 및 교량 등의 피해에 큰 연관성이 있기 때문으로 유추된다. 개발된 취약도 곡선으로부터 보통 이상(DL > 1)의 피해에 대해 SA_T3.0 = 0.1g일 때 2%의 피해확률을 예측하였으며, SA_T3.0 = 0.2g일 때 23.9%의 피해확률을 예측하였다.

• 한국물환경학회지
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• 제34권1호
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• pp.1-9
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• 2018

In this study, the load of the river was calculated by using the actual data of the Yeong-bon C1, Yeong-bon C2, Yeong-bon C3 monitoring points of the Yeong-san river watershed to determine the excess. As a result, the BOD is 75.83 % at the Yeong-bon C1 and the five-year average value is higher than at other points. The Yeong-bon C3 was 72.15 % and Yeong-bon C2 was analyzed as 68.78 %. The five-year average of the T-P was 71.95 % for the Yeong-bon C2 and 69.86 % for the Yeong-bon C3 and 69.16 % for Yeong-bon C1; these levels exceeded the target water quality standards of 50 %. As a result of analyzing the pollutant load, we found that the Yeong-bon C1 has been highly affected by the nonpoint pollution source because the excess rate is high in the upper section of the flow rate. The Yeong-bon C2 showed a high excess rate in the lower part of the flow rate, and it was estimated that the influence of the point pollution source was large. The excess rate of the Yeong-bon C3 is small in the interval deviation, and it was evaluated as being affected by both point and non-point pollution sources. The TMDL monitoring network data were used to estimate the exceed ratio for the target water quality assessment, and the implementation evaluation was made by the flow exceedance probability interval to analyze the monitoring data so that the data could be utilized according to the purpose of the measurement network.

• 한국화재소방학회논문지
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• 제31권1호
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• pp.26-35
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• 2017

미국 노스리지 지진(1994)과 일본 고베지진(1995) 발생 이후 다양한 구조물 및 건축물을 설계 할 때 성능기반 내진설계 개념을 적용하고 있다. 최근 국내 소방시설물에 대해서도 내진설계기준이 제정되어 내진설계 규정에 따라 적합하게 설계되어야 한다. 성능기반 설계가 도입되면서 구조물 중요도에 따라 기능수행, 즉시복구, 인명보호, 붕괴방지 등 각각의 성능에 적합한 연발생빈도의 등재해도 스펙트럼이 요구되고 있다. 확률론적 방법을 적용하여 국내 주요 5개 도시에 대해 등재해도 스펙트럼(uniform hazard spectrum)을 분석하였다. 지진 및 지체구조 관련된 전문가 패널은 10인이며 전문가 패널이 제시한 다수의 지진지체구조구 모델 및 다양한 지진동 감쇠식을 적용하였다. 분석대상 진동수는 (0.5, 1.0, 2.0, 5.0, 10.0) Hz이고 또한 PGA(최대지반가속도) 결과를 이용하여 500년, 1,000년 및 2,500년 등 3개 주요 성능기준에 해당하는 재현주기에 대해 등재해도 스펙트럼을 분석하였다. 민감도 분석에 의하면 지진지체구조 구 모델 변수보다 지반진동 감쇠식 변수가 지진재해도에 보다 큰 영향을 주는 것으로 분석되었다. 일반적으로 등재해도 스펙트럼은 10 Hz에서 최대 지진재해도를 보여 주었고, 기존 연구 및 관련 기술기준에 제시된 등재해도 스펙트럼의 수준 및 모양 특성과 대단히 유사하였다.

• 한국지구과학회지
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• 제37권3호
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• pp.162-172
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• 2016

최근 미국 노스리지 지진(1994)과 일본 고베 지진(1995) 발생 이후 다양한 구조물 및 건축물을 설계할 때 성능 기반 설계 개념이 적극적으로 도입되고 있다. 성능기반 설계가 도입되면서 구조물 각각의 성능에 적합한 연발생빈도의 등재해도 스펙트럼이 요구되고 있다. 10 인의 지진 및 지체구조 전문가가 제시한 국내 및 미국 중동부에서 개발된 스펙트럴 지반진동 감쇠식과 다수의 지진지체구조구 모델을 사용하였다. 인구 밀도가 높은 5개 주요 도시에 대해 확률론적 방법을 이용하여 등지진재해도 스펙트럼을 분석하였다. 0.5, 1.0, 2.0, 5.0, 10.0 Hz 및 PGA에 대해 확률론적 지진재해도 결과를 이용하여 500년, 1,000년 및 2,500년의 3개 재현주기에 대해 등재해도 스펙트럼을 분석하였다. 민감도 분석 결과 각각의 고유 진동수에 해당하는 지반진동 감쇠식이 지진지체구조구 모델에 비하여 지진재해도에 보다 커다란 영향을 주었다. 마지막으로 등재해도 스펙트럼은 공통적으로 10 Hz에서 최대값을 보여 주었고, 원자력 관련 기술기준 또는 기존 연구에서 제시된 등지진재해도 스펙트럼과 수준과 모앙 특성에서 유사성을 보여주었다.