• Journal of the Earthquake Engineering Society of Korea
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• v.17 no.2
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• pp.71-77
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• 2013

The uniform hazard spectra for seven major cities in Korea, Seoul, Daejeon, Daegu, Busan, Gwangju, Ulsan, and Inchon are suggested. Probabilistic seismic hazard analyses were performed using the attenuation equations derived from seismology research in Korea since 2000 and the seismotectonic models selected by expert assessment. For the estimation of the uniform hazard spectra, the seismic hazard curves for several frequencies and PGAs were calculated by using the spectral attenuation equations. The seismic hazards (annual exceedance probability) calculated for the 7 metropolises ranged from about $1.4305{\times}0^{-4}/yr$ to $1.7523{\times}10^{-4}/yr$ and averaged out at about $1.5902{\times}10^{-4}/yr$ with a log standard deviation of about 0.085 at 0.2 g. The uniform hazard spectra with recurrence intervals of 500, 1000, and 2500 years estimated by using the calculated mean seismic hazard on the frequencies presented peak values at 10.0 Hz, and the log standard deviations of the difference between metropolises ranged from about 0.013 to 0.209. In view of the insignificant difference between the estimated uniform hazard spectra obtained for the considered metropolises, the mean uniform hazard spectrum was estimated. This mean uniform hazard spectrum is expected to be used as input seismic response spectrum for rock sites in Korea.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.10a
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• pp.297-303
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• 1998

The uniform hazard spectrum of Wolsong Nuclear Power plant Site is computed in order to estimate probabilistically the characteristics of spectral ground response. The spectral hazard values calculated from the seismic zoning maps proposed by eight seismologist are combined with equal weight to produce a uniform hazard spectrum. The uniform hazardd spectra corresponding to reference probabilities of 1.0 $\times$10-4/year and 1.0$\times$10-5/year are presented, which largely depend on the spectral attenuation relation. The computational results of this study contribute to verify the conservatism of the design ground spectrum of Wolsong Nuclear Power Plant.

• Fire Science and Engineering
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• v.31 no.1
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• pp.26-35
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• 2017

Since the Northridge earthquake (1994) and Kobe earthquake (1995), the concept of performance-based design has been actively introduced to design major structures and buildings. Recently, the seismic design code was established for fire protection facilities. Therefore, the important fire protection facilities should be designed and constructed according to the seismic design code. Accordingly, uniform hazard spectra (UHS), with annual exceedance probabilities, corresponding to the performance level, such as operational, immediate occupancy, life safety, and collapse prevention, are required for performance-based design. Using the method of probabilistic seismic hazard analysis (PSHA), the uniform hazard spectra for 5 major cities in Korea with a recurrence period of 500, 1,000, and 2,500 years corresponding to frequencies of (0.5, 1.0, 2.0, 5.0, 10.0)Hz and PGA, were analyzed. The expert panel was comprised of 10 members in seismology and tectonics. The ground motion prediction equations and several seismo tectonic models suggested by 10 expert panel members in seismology and tectonics were used as the input data for uniform hazard spectrum analysis. According to sensitivity analysis, the parameter of spectral ground motion prediction equations has a greater impact on the seismic hazard than seismotectonic models. The resulting uniform hazard spectra showed maximum values of the seismic hazard at a frequency of 10Hz and also showed the shape characteristics, which are similar to previous studies and related technical guides for nuclear facilities.

• Journal of the Korean earth science society
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• v.37 no.3
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• pp.162-172
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• 2016

Since the Northridge earthquake in 1994 and the Kobe earthquake in 1995 occurred, the concept of performance based design has been introduced for designing various kinds of important structures and buildings. Uniform hazard spectra (UHS), with annual exceedance probabilities, corresponding to the performance level of each structure, are required for performance-based design. The probabilistic seismic hazard analysis was performed using spectral ground motion prediction equations, which were developed from both Korean Peninsula and Central and Eastern US region, and several seismotectonic models suggested by 10 expert panel members in seismology and tectonics. The uniform hazard spectra for 5 highly populated cities in Korea, with recurrence period of 500, 1,000, and 2,500 years using the seismic hazard at the frequencies of 0.5, 1.0, 2.0, 5.0, 10.0 Hz and Peak ground acceleration (PGA) were analyzed using the probabilistic seismic hazard analysis. The sensitivity analysis suggests that spectral ground motion prediction equations impact much more on seismic hazard than what seismotectonic models do. The uniform hazard spectra commonly showed a maximum hazard at the frequency of 10 Hz and also showed the similar shape characteristics to the previous study and related technical guides to nuclear facilities.

• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.6
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• pp.301-309
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• 2019

A methodology to assess seismic fragility of a nuclear power plant (NPP) using a conditional mean spectrum is proposed as an alternative to using a uniform hazard response spectrum. Rather than the single-scenario conditional mean spectrum, which is the conventional conditional mean spectrum based on a single scenario, a multi-scenario conditional mean spectrum is proposed for the case in which no single scenario is dominant. The multi-scenario conditional mean spectrum is defined as the weighted average of different conditional mean spectra, each one of which corresponds to an individual scenario. The weighting factors for scenarios are obtained from a deaggregation of seismic hazards. As a validation example, a seismic fragility assessment of an NPP containment structure is performed using a uniform hazard response spectrum and different single-scenario conditional mean spectra and multi-scenario conditional mean spectra. In the example, the number of scenarios primarily influences the median capacity of the evaluated structure. Meanwhile, the control frequency, a key parameter of a conditional mean spectrum, plays an important role in reducing logarithmic standard deviation of the corresponding fragility curves and corresponding high confidence of low probability of failure (HCLPF) capacity.

• Journal of the Korean GEO-environmental Society
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• v.10 no.7
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• pp.111-115
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• 2009

In Korea, the probabilistically developed seismic hazard maps are used with deterministically derived seismic site coefficients in developing the design response spectrum of a specific site. Even though the seismic hazard maps and seismic site coefficients are incompatible, the current design code ignores such incompatibility. If the seismic hazard map and seismic coefficients are both developed in identical probabilistic framework, such problems can be solved. Unfortunately, the available method cannot be use to derive "true" probabilistic site coefficients. This study uses the ground motion time histories, which were developed as the result of a new probabilistic seismic hazard analysis in the companion paper, as input motions in performing one-dimensional equivalent linear site response analyses, from which the uniform hazard response spectra are generated. Another important characteristic of the hazard response spectra are that the uncertainties and randomness of the ground properties are accounted for. The uniform hazard spectra are then used to derive probabilistic site coefficients. Comparison of probabilistic and deterministically site coefficients demonstrate that there is a distinct discrepancy between two coefficients.

• Earthquakes and Structures
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• v.8 no.3
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• pp.681-697
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• 2015

Iran as one of the countries located on the Alpine-Himalayan seismic belt has recently experienced a few number of catastrophic earthquakes. A well-known index of how buildings are affected by earthquakes is through assessment of probable Peak Ground Acceleration (PGA) and structures' response spectra. In this research, active faults around Kerman and Birjand, two major cities in eastern parts of Iran, have been considered. Seismic catalogues are gathered to categorize effects of surrounding faults on seismicity of the region. These catalogues were further refined with respect to time and space based on Knopoff-Gardner algorithm in order to increase statistical independency of events. Probabilistic Seismic Hazard Analysis (PSHA) has been estimated for each of cities regarding 50, 100, 200 and 500 years of structures' effective life-span. These results subsequently have been compared with Deterministic Seismic Hazard Analysis (DSHA). It has been observed that DSHA not necessarily suggests upper bound of PSHA results. Furthermore, based on spectral Ground Motion Prediction Equations (GMPEs), Uniform Hazard Spectra (UHS) and spectral acceleration were provided for 2% and 10% levels of probability of exceedance. The results show that increasing source-to-site distance leads to spectral acceleration reduction regarding each fault. In addition, the spectral acceleration rate of variation would increase if the source-to-site distance decreases.

• Nuclear Engineering and Technology
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• v.41 no.10
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• pp.1243-1254
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• 2009

The paper discusses the methodology and the use of probabilistic seismic hazard analysis (PSHA) for nuclear power plants from a European perspective. The increasing importance of risk-informed approaches in the nuclear oversight process observed in many countries has contributed to increasing attention to PSHA methods. Nevertheless significant differences with respect to the methodology of PSHA are observed in Europe. The paper gives an overview on actual projects and discusses the differences in the PSHA-methodology applied in different European countries. These differences are largely related to different approaches used for the treatment of uncertainties and to the use of experts. The development of a probabilistic scenario-based approach is identified as a meaningful alternative to the development of uniform hazard spectra or uniform confidence spectra.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.3
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• pp.35-42
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• 2012

We propose a probabilistic method to evaluate the uniform hazard spectra (UHS) of the soil of nuclear power plant(NPP) sites corresponding to that of a bedrock site. To do this, amplification factors on the surface of soil sites were estimated through site response analysis while considering the uncertainty in the earthquake ground motion and soil deposit characteristics. The amplification factors were calculated by regression analysis with spectral acceleration because these two factors are mostly correlated. The proposed method was applied to the evaluation of UHS for the KNGR (Korean Next Generation Reactor) and the APR1400 (Advanced Power Reactor 1400) nuclear power plant sites of B1, B4, C1 and C3. The most dominant frequency range with respect to the annual frequency of earthquakes was evaluated from the UHS analysis. It can be expected that the proposed method will improve the results of integrated risk assessments of NPPs rationally. We expect also that the proposed method will be applied to the evaluation of the UHS and of many other kinds of soil sites.

• Structural Engineering and Mechanics
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• v.37 no.2
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• pp.233-251
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• 2011

The seismic provisions of the current edition (2005) of the National Building Code of Canada (NBCC) differ significantly from the earlier edition. The current seismic provisions are based on the uniform hazard spectra corresponding to 2% probability of exceedance in 50 years, as opposed to the seismic hazard level with 10% probablity of exeedance in 50 years used in the earlier edition. Moreover, the current code is presented in an objective-based format where the design is performed based on an acceptable solution. In the light of these changes, an assessment of the expected performance of the buildings designed according to the requirements of the current edition of NBCC would be very useful. In this paper, the seismic performance of a set of six, twelve, and eighteen story buildings of regular geometry and with concrete moment resisting frames, designed for Vancouver western Canada, has been evaluated. Although the effects of non-structural elements are not considered in the design, the non-structural elements connected to the lateral load resisting systems affect the seismic performance of a building. To simulate the non-structural elements, infill panels are included in some frame models. Spectrum compatible artificial ground motion records and scaled actual accelerograms have been used for evaluating the dynamic response. The performance has been evaluated for each building under various levels of seismic hazard with different probabilities of exceedance. From the study it has been observed that, although all the buildings achieved the life-safety performance as assumed in the design provisions of the building code, their performance characteristics are found to be non-uniform.