• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.6
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• pp.329-339
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• 2019

The strategy for the management of earthquakes is shifting from post recovery to prevention; therefore, seismic performance management requires quantitative predictions of damage and the establishment of strategies for initial responses to earthquakes. Currently, seismic performance evaluation for seismic management in Korea consists of two stages: preliminary evaluation and detailed evaluation. Also, the priority of seismic performance management is determined in accordance with the preliminary evaluation. As a deterministic method, preliminary evaluation quantifies the physical condition and socio-economic importance of a facility by various predetermined indices, and the priority is decided by the relative value of the indices; however, with the deterministic method it is difficult to consider any uncertainty related to the return-year, epicenter, and propagation of seismic energy. Also this method cannot support tasks such as quantitative socio-economic damage and the provision of data for initial responses to earthquakes. Moreover, indirect damage is often greater than direct damage; therefore, a method to quantify damage is needed to enhance accuracy. In this paper, a Seismic Risk Assessment is used to quantify the cost of damage of road facilities in Pohang city and to support decision making.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.14 no.2
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• pp.32-40
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• 2018

Since 2000, the frequency of earthquakes beyond the 5.0 magnitude quake has been increasing in the Korean peninsula. For instance, the 5.0-magnitude earthquake in Baekryong-do in 2003 has occurred, and recent earthquake with Gyeongju(2016) and Pohang(2017) measured respectively magnitude of 5.2 and 5.8 on the Richter scale. As results, the public concern and anxiety about earthquakes are increasing, and therefore it is necessarily required for social infrastructure to reinforce seismic design and energy production facilities directly related to the national economy and security. This study represents the analysis of seismic performance evaluation methodology such as Seismic Margin Assessment (SMA), Seismic Probabilistic Risk Assessment (SPRA), High Confidence Low Probability Failure (HCLPF) in nuclear power plants in order to develop optimal seismic performance improvement. Current methodologies to evaluate nuclear power plants are also addressed. Through review of the nuclear structure evaluation past and current trend, it contributes to be the basis for the improvement of evaluation techniques on the next generation of nuclear power plants.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.3
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• pp.121-128
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• 2021

Piloti-type buildings in Korea are usually composed of lower frames and upper shear wall structures. Piloti-type buildings have been seriously damaged during earthquakes because of the construction of soft and weak stories. Piloti-type buildings with edge cores are two-way unsymmetric planes. This paper analyzed and obtained the dynamic response for structures modeled using a multistory two-way asymmetric system. The numerical results, obtained using the Newmark-β method, show the time-history responses and trends of maximum displacements and shear forces. The purpose of this study is to evaluate the effect of reinforcement on dynamic response when a shear wall or brace is reinforced in the corner opposite the piloti.

• Korean Journal of Agricultural Science
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• v.50 no.3
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• pp.469-484
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• 2023

In this study, three types of structures-stepped gabion retaining walls, vertical gabion retaining walls, and parapets-were installed on the dam floor crest to prevent the overflow of deteriorative homogeneous reservoirs. The acceleration response, displacement behavior, and pore water pressure ratio behavior were compared and evaluated using shaking-table model tests. The experimental conditions were set to 0.154 g in consideration of the domestic standard and the seismic acceleration range according to the magnitude of the earthquake, and the input waveform was applied with Pohang, Gongen, and artificial earthquake waves. The acceleration response according to the design ground acceleration increased as the height of the embankment increased, and the observed value were larger in the range of 1.1 to 2.1 times the input acceleration for all structures. The horizontal and vertical displacements exhibited maximum values on the upstream slope, and the embankment was evaluated as stable and included within the allowable range for all waveforms. The settlement ratio considering the similarity law exhibited the least change in the case of the parapet structure. The amplification ratio was 1.1 to 1.5 times in all structures, with the largest observed in the dam crest. The maximum excess pore water pressure ratio was in the range of 0.010 - 0.021, and the liquefaction evaluation standard was within 1.0, which was considered very stable.

• Economic and Environmental Geology
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• v.51 no.2
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• pp.149-166
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• 2018

Many large earthquakes have continuously been reported and resulted in significant human casualties and extensive damages to properties globally. The accident of Fukushima nuclear power plant in Japan was caused by a mega-tsunami, which is a secondary effect associated with the Tohoku large earthquake (M=9.0, 2011. 3. 11.). Most earthquakes occur by reactivation of pre-existing active faults. Therefore, the importance of paleoseismological study have greatly been increased. The Korean peninsula has generally been considered to be a tectonically stable region compared with neighboring countries such as Japan and Taiwan, because it is located on the margin of the Eurasian intra-continental region. However, the recent earthquakes in Gyeongju and Pohang have brought considerable insecurity on earthquake hazard. In particular, this region should be secure against earthquake, because many nuclear facilties and large industrial facilities are located in this area. However, some large earthquakes have been reported in historic documents and also several active faults have been reported in southeast Korea. This study explains the evaluation methods of geological structures on active fault, fault damage zone, the relationship between earthquake and active fault, and respect distance. This study can contribute to selection of safe locations for nuclear facilities and to earthquake hazards and disaster prevention.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.6
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• pp.821-831
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• 2019

The 9.12 earthquake (2016.9.12., M_L=5.8) and Pohang (2017.11.15., M_L=5.4) caused social and economic damage, resulting in a greater public interest in earthquakes than in the past. In the U.S., Japan and Chile, which have high frequency of earthquakes, infrastructure facilities are already managed based on probabilistic seismic hazard analysis (PSHA) and ground motion prediction equation (GMPE) to prepare for and respond to seismic disasters. In South Korea, the aforementioned PSHA and GMPE models have been developed independently through individual researchers. However, the limited disclosure of basic data, calculation methods, and final results created during the model development poses a problem of deploying new data without updating the earthquake that occurs every year. Therefore, this paper describes how to create flatfile, which is the basic data of GMPE, and how to process for seismic waves, and how to create intensity measures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.4
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• pp.353-362
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• 2020

Korea was recognized as a relatively safe area for earthquake. However, due to considerable damage to facilities caused by the earthquake in Gyeongju and Pohang, interest in the maintenance and repair of structures is increasing. So interest in vibration damping technology applicable to existing structures is also increasing. However, vibration damping technology has a problem in that its usability is reduced due to damage of the damping device when a strong earthquake occurs. Recently, in order to solve such a problem, study is being conducted to apply a superelastic shape memory alloys (SSMA) capable of recentering bracing. Therefore, in this study, nonlinear dynamic analysis is performed to evaluate the seismic performance of the buckling-restrained braced frame (BRBF) applied SSMA to bracing.

• Journal of the Korean Geophysical Society
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• v.1 no.1
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• pp.23-30
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• 1998

Fault-plane solutions of the December 13, 1996 Yeongweol earthquake with magnitude 4.5 is obtained using the grid test technique. Thirty polarities of P waves recorded at KMA, KIGAM, KSRS and JAPAN stations are used for the event. The obtained fault plane solution shows strike-slip motion with significant amount of thrust component. The orientation of the fault is 180±20° in strike, 50±5° in dip and 150±5° in rake, or 292±3° in strike, 65±5° in dip and 30±10° in rake. These solutions are similar to those of earthquakes occurred at Sagju (Jan. 7, 1980), Pohang (Apr. 15, 1981) and offshore Gunsan (Oct. 6, 1976). The compressional axis of the stress field is trending from ENE to WSW, which is consistent with the previously defined typical regional tectonic stress orientation in and around Korean Peninsula.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.2
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• pp.15-22
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• 2020

In this paper, seismic ground motion generation method based on the observbation data from the Korea Meteorological Administration is proposed to predict the acceleration time history at an arbitrary location after earthquake. The proposed method assumes that the magnitude of the seismic accelrations obtained from the near stations decreases linearly with the distance from the epicenter to the corresponding station and the accelerations measured at the adjacent stations are assumed to have similar maximum acceleration and time shape functions. These two assumptions allow for the prediction of seismic acceleartion motion without geotechnical information where no seismic accelerometer is installed. This study verified the applicability of the prediction method using seismic observation data from Gyeongju Earthquake (2016), Pohang Earthquake (2017) and Sangju Earthuqkae (2019). The comparison results show that the proposed method is effective for predicting the seismic acceleration response spectrum and time history at arbitary locations.

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.5
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• pp.197-209
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• 2020

Evidence of liquefaction during the 2017 Pohang earthquake has highlighted the urgent need to evaluate the current seismic design standard for liquefaction in Korea, particularly the liquefaction triggering standard. With the simplified method, which is the most popular method for evaluating liquefaction triggering, the factor of safety for liquefaction triggering is calculated via the cyclic stress ratio (CSR) and the cyclic resistance ratio (CRR). The parameters in the CSR and CRR have undergone changes over time based on new research findings and lessons learned from liquefaction case-histories. Hence, the current design standard for liquefaction triggering evaluation in Korea should also reflect these changes to achieve seismic safety during future earthquakes. In this study, liquefaction susceptibility criteria were discussed initially and this was followed by a review of the current liquefaction triggering codes/guidelines in other countries and Korea. Next, the parameters associated with the CSR such as the maximum ground acceleration, stress reduction factor, magnitude scaling factor, and overburden correction factor were discussed in detail. Then, the evaluation of the CRR using the SPT N-value and CPT qc-value was elaborated along with overburden and clean-sand correction factors. Based on this review of liquefaction triggering evaluation standards, recommendations are made for improving the current seismic design standard related to liquefaction triggering in Korea.