• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.257-259
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• 2008

Acceleration time history (ATH) used in the seismic analysis should envelop a target power spectral density (PSD) function in addition to the design response spectrum in order to have sufficient energy at each frequency for the purpose of ensuring adequate load. Even though design regulations require the ATH used in seismic analysis to meet a target PSD function, the reason that ATHs meet to a target PSD function is not described. Thus, artificial ATHs for high PSD function and artificial ATHs for low PSD function are generated. And then elastic and inelastic single-degree-of-freedom (SDOF) systems are loaded with these artificial time histories as the earthquake load. As a result, linear response and inelastic response of SDOF systems are affected by PSD function.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.265-268
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• 2008

The safety of a tunnel under seismic motion is most often evaluated by ovalling deformation of tunnel. This paper research about tunnel's longitudinal deformation. Because of spatial variation of seismic ground motion, the longitudinal structures like tunnel are likely to experience relative displacements along longitudinal direction. The spatially variable ground motion can be estimated by coherency function obtained empirically, and can be considered from different arrival times of ground motion. As a result of estimating tunnel's relative displacements at maximum curvature of tunnel, the displacements and curvatures estimated by coherency function affect the tunnel's safety more than different arrival times. However, if tunnel's displacements by coherency function superpose on displacements by different arrival times, the relative displacements and curvatures of tunnel will be more severe. Therefore, to estimate accurately tunnel's deformation in longitudinal direction has to consider both coherency and wave passage effects.

• Earthquakes and Structures
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• v.18 no.2
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• pp.163-170
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• 2020

Floor acceleration plays a major role in the seismic design of nonstructural components and equipment supported by structures. Large floor acceleration may cause structural damage to or even collapse of buildings. For precision instruments in high-tech factories, even small floor accelerations can cause considerable damage in this study. Six P-wave parameters, namely the peak measurement of acceleration, peak measurement of velocity, peak measurement of displacement, effective predominant period, integral of squared velocity, and cumulative absolute velocity, were estimated from the first 3 s of a vertical ground acceleration time history. Subsequently, a new predictive algorithm was developed, which utilizes the aforementioned parameters with the floor height and fundamental period of the structure as the new inputs of a support vector regression model. Representative earthquakes, which were recorded by the Structure Strong Earthquake Monitoring System of the Central Weather Bureau in Taiwan from 1992 to 2016, were used to construct the support vector regression model for predicting the peak floor acceleration (PFA) of each floor. The results indicated that the accuracy of the predicted PFA, which was defined as a PFA within a one-level difference from the measured PFA on Taiwan's seismic intensity scale, was 96.96%. The proposed system can be integrated into the existing earthquake early warning system to provide complete protection to life and the economy.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.269-272
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• 2008

The seismic fragility curves of a structure represents the probability of exceeding the prescribed structural damage given various levels of ground motion intensityand the seismic fragility curve is essential to evaluation of structural performance and assessment of risk and loss of structures. The purpose of this paper is to develop seismic fragility functions for bridge structures in Koreaby reviewing those of advanced countries. Therefore, at first, we investigated development conditions of the seismic fragility functions. And the next highway bridges in Korea are classified into a number of categories and several typical bridges are selected to estimate seismic fragilities for using this analysis method in Korea. Finally, fragility curves for PSC Box girder bridge are estimated. The results show that the bridge classification and damage state play an important role in estimation of seismic damage and seismic fragility analysis for bridge structures.

• Earthquakes and Structures
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• v.27 no.3
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• pp.227-237
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• 2024

The incidence angle of seismic excitation relative to the two orthogonal major axes of structures has been a subject of considerable research interest. Previous studies have primarily focused on single-storey symmetric and asymmetric structures, suggesting a minimal effect of incidence angle on structural behavior. This research extends the investigation to multi-storey structures, including vertically irregular configurations, using a comprehensive set of 20 near fault and 20 far field seismic excitation. The study employs nonlinear time-history analysis with a bidirectional hysteresis model to capture inelastic deformations accurately. Various structural models, including one-storey and two- storey regular structures (R1, R2) and vertically irregular structures with setbacks in one direction (IR1) and both directions (IR2), are analysed. The analysis reveals that the incidence angle has no discernible impact over the response of regular multi-storey structures. However, vertically irregular structures exhibit notable responses at corner columns, which decrease towards central columns, irrespective of the incidence angle. This response is attributed to the inherent mass distribution and stiffness irregularities rather than the angle of seismic excitation. The findings indicate that for both near fault and far field seismic excitation, the incidence angle's impact remains marginal even for complex structural configurations. Consequently, the study suggests that the angle of incidence of seismic excitation need not be a primary consideration in the seismic design of both regular and vertically irregular structures. These conclusions are robust across various structural models and seismic excitation characteristics, providing a comprehensive understanding the impact of incidence angle on seismic response.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.563-574
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• 2008

Most of earthquake-induced geotechnical hazards have been caused by the site effects relating to the amplification of ground motion, which are strongly influenced by the local geologic conditions such as soil thickness or bedrock depth and soil stiffness. In this study, an integrated GIS-based information system for geotechnical data, called geotechnical information system (GTIS), was constructed to establish a regional counterplan against earthquake-induced hazards at an urban area, Daejeon, which is represented as a hub of research and development in Korea. To build the GTIS for the area of interesting, pre-existing geotechnical data collections were performed across the extended area including the study area and a walk-over site survey was additionally carried out to acquire surface geo-knowledge data. For practical application of the GTIS used to estimate the site effects at the area of interesting, seismic microzoning map of the characteristic site period was created and presented as regional synthetic strategy for earthquake-induced hazards prediction. In addition, seismic zonation for site classification according to the spatial distribution of the site period was also performed to determine the site amplification coefficients for seismic design and seismic performance evaluation at any site in the study area. Based on the case study on seismic zonations at Daejeon, it was verified that the GIS-based GTIS was very useful for the regional prediction of seismic hazards and also the decision support for seismic hazard mitigation.

• 한국방재학회:학술대회논문집
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• 2009.02b
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• pp.43-50
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• 2009

Strong ground motion attenuation relationship represents a comprehensive trend of ground shakings at sites with distances from the source, geology, local soil conditions, and others. It is necessary to develop an attenuation relationship with careful considerations of characteristics of the target area for reliable seismic hazard/risk assessments. In the study, observed ground motions from the January 2007 magnitude 4.9 Odaesan earthquake and the events occurring in the Gyeongsang provinces are compared with the previously proposed ground attenuation relationships in the Korean Peninsula to select most appropriate one. In the meantime, a few strong ground motion attenuation relationships are proposed and introduced in HAZUS, which have been designed for the Western United States and the Central and Eastern United States. The selected relationship from the ones for the Korean Peninsula has been compared with attenuation relationships available in HAZUS. Then, the attenuation relation for the Western United States proposed by Sadigh et al. (1997) for the Site Class B has been selected for this study. Reliability of the assessment will be improved by using an appropriate attenuation relation. It has been used for the earthquake loss estimation of the Gyeongju area located in southeast Korea using the deterministic method in HAZUS with a scenario earthquake (M=6.7). Our preliminary estimates show 15.6% damage of houses, shelter needs for about three thousands residents, and 75 life losses in the study area for the scenario events occurring at 2 A.M. Approximately 96% of hospitals will be in normal operation in 24 hours from the proposed event. Losses related to houses will be more than 114 million US dollars. Application of the improved methodology for loss estimation in Korea will help decision makers for planning disaster responses and hazard mitigation.

• Journal of the Korean Geotechnical Society
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• v.25 no.1
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• pp.5-19
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• 2009

Most of earthquake-induced geotechnical hazards have been caused by the site effects relating to the amplification of ground motion, which is strongly influenced by the local geologic conditions such as soil thickness or bedrock depth and soil stiffness. In this study, an integrated GIS-based information system for geotechnical data, called geotechnical information system (GTIS), was constructed to establish a regional counterplan against earthquake-induced hazards at an urban area of Daejeon, which is represented as a hub of research and development in Korea. To build the GTIS for the area concerned, pre-existing geotechnical data collections were performed across the extended area including the study area and site visits were additionally carried out to acquire surface geo-knowledge data. For practical application of the GTIS used to estimate the site effects at the area concerned, seismic zoning map of the site period was created and presented as regional synthetic strategy for earthquake-induced hazards prediction. In addition, seismic zonation for site classification according to the spatial distribution of the site period was also performed to determine the site amplification coefficients for seismic design and seismic performance evaluation at any site in the study area. Based on this case study on seismic zonations in Daejeon, it was verified that the GIS-based GTIS was very useful for the regional prediction of seismic hazards and also the decision support for seismic hazard mitigation.

• Geophysics and Geophysical Exploration
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• v.13 no.3
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• pp.268-276
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• 2010

Earthquake Hazard Mitigation Law was activated into force on March 2009. By the law, the obligation to monitor the effect of earthquake on the facilities was extended to many organizations such as gas company and local governments. Based on the estimation of National Emergency Management Agency (NEMA), the number of free-surface acceleration stations would be expanded to more than 400. The advent of internet protocol and the more simplified operation have allowed the quick and easy installation of seismic stations. In addition, the dynamic range of seismic instruments has been continuously improved enough to evaluate damage intensity and to alert alarm directly for earthquake hazard mitigation. For direct visualization of damage intensity and area, Real Time Intensity COlor Mapping (RTICOM) is explained in detail. RTICOM would be used to retrieve the essential information for damage evaluation, Peak Ground Acceleration (PGA). Destructive earthquake damage is usually due to surface waves which just follow S wave. The peak amplitude of surface wave would be pre-estimated from the amplitude and frequency content of first arrival P wave. Earthquake Early Warning (EEW) system is conventionally defined to estimate local magnitude from P wave. The status of EEW is reviewed and the application of EEW to Odesan earthquake is exampled with ShakeMap in order to make clear its appearance. In the sense of rapidity, the earthquake announcement of Korea Meteorological Agency (KMA) might be dramatically improved by the adaption of EEW. In order to realize hazard mitigation, EEW should be applied to the local crucial facilities such as nuclear power plants and fragile semi-conduct plant. The distributed EEW is introduced with the application example of Uljin earthquake. Not only Nation-wide but also locally distributed EEW applications, all relevant information is needed to be shared in real time. The plan of extension of Korea Integrated Seismic System (KISS) is briefly explained in order to future cooperation of data sharing and utilization.

• Journal of the Korean earth science society
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• v.29 no.7
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• pp.559-566
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• 2008

Ground shaking recorded during the January 20, 2007, $M_L$ 4.8 Odaesan earthquake (Korea) were used to investigate the role of the crustal structure in producing a strong ground motion, which includes the identification of the phases responsible for the strong ground motion and their implications for seismic hazard assessment. Analyses of strong-motion data together with waveform simulation revealed that critical and post-critical reflections from the crust-mantle boundary are responsible for the abnormal ground motions. This result demonstrates that the crustal structure should be taken into consideration in studies of seismic hazard mitigation even in the areas of relatively low seismicity.