• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.1
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• pp.21-28
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• 1999

The objective of the study is to develop attenuation equations of the ground motions in the southern part of the Korean peninsula. The earthquake source characteristics and the medium properties were estimated from available instrumental earthquake records and used as input parameters. The peak ground accelerations(PGA) and pseudo-velocity response spectra(PSV) were simulated by the random vibration theory. The attenuation equations for the PGA and PSV were constructed in terms of local magnitudes and hypocentral distances.

• Earthquakes and Structures
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• v.11 no.2
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• pp.327-346
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• 2016

The 2012 Emilia (Italy) earthquakes struck a highly industrialized area including several thousands of industrial prefabricated buildings. Due to the lack of specific design and detailing for earthquake resistance, precast reinforced concrete (RC) buildings suffered from severe damages and even partial or total collapses in many cases. The present study reports a data inventory of damages from field survey on prefabricated buildings. The damage database concerns more than 1400 buildings (about 30% of the total precast building stock in the struck region). Making use of the available shakemaps of the two mainshocks, damage distributions were related with distance from the nearest epicentre and corresponding Pseudo-Spectral Acceleration for a period of 1 second (PSA at 1 s) or Peak Ground Acceleration (PGA). It was found that about 90% of the severely damaged to collapsed buildings included into the database stay within 16 km from the epicentre and experienced a PSA larger than 0.12 g. Moreover, 90% of slightly to moderately damaged buildings are located at less than 25 km from the epicentre and were affected by a PSA larger than 0.06 g. Nevertheless, the undamaged buildings examined are almost uniformly distributed over the struck region and 10% of them suffered a PSA not lower than 0.19g. The damage distributions in terms of the maximum experienced PGA show a sudden increase for $PGA{\geq}0.28g$. In this PGA interval, 442 buildings were collected in the database; 55% of them suffered severe damages up to collapse, 32% reported slight to moderate damages, whereas the remaining 13% resulted undamaged.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.1
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• pp.37-45
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• 2012

In an effort to further exploit the peak ground-motion acceleration (PGA) information per second available in real time by the enacted law, bracketed summations of the PGA per second ($BSPGA_k$) for 30 seconds based on the records with a rate of 100 samples were compared with the cumulative absolute velocity (CAV) and earthquake intensities based on a worldwide database of records from small-to-large earthquakes. The CAV, currently in use as an earthquake damage indicator for nuclear power plants due to its strong correlation with the earthquake intensity, has the disadvantage of requiring a massive amount of digital data with a rate of more than 100 samples per second. The comparative study shows that the $BSPGA_k$ is well correlated with the CAV over the wide range of strong ground-motion levels, which suggests that the $BSPGA_k$ is one of the new promising ground-motion parameters especially useful for rapid earthquake alert notifications through an earthquake monitoring network. Based on the domestic database of records from small-to-moderate earthquakes with felt reports, it is also observed that the $BSPGA_k$ is comparable to the CAV and better than the PGA in predicting the intensity by using the correlation relation.

• Structural Engineering and Mechanics
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• v.42 no.5
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• pp.631-644
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• 2012

Current seismic codes require from the seismically designed structures to be capable to withstand inelastic deformation. Many studies dealt with the development of different inelastic spectra with the aim to simplify the evaluation of inelastic deformation and performance of structures. Recently, the concept of inelastic spectra has been adopted in the global scheme of the performance-based seismic design through capacity-spectrum methods. In this paper, the median of the ductility demand ratio for 80 ground motions are presented for different levels of normalized yield strength, defined as the yield strength coefficient divided by the peak ground acceleration (PGA). The influence of the post-to-preyield stiffness ratio on the ductility demand is investigated. For fixed levels of normalized yield strength, the median ductility versus period plots demonstrated that they are independent of the earthquake magnitude and epicentral distance. Determined by regression analysis of the data, two design equations have been developed; one for the ductility demand as function of period, post-to-preyield stiffness ratio, and normalized yield strength, and the other for the inelastic deformation as function of period and peak ground acceleration valid for periods longer than 0.6 seconds. The equations are useful in estimating the ductility and inelastic deformation demands for structures in the preliminary design. It was found that the post-to-preyield stiffness has a negligible effect on the ductility factor if the yield strength coefficient is greater than the PGA of the design ground motion normalized by gravity.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.5
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• pp.35-44
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• 2011

PGA (Peak Ground Acceleration) is the parameter which indicates the peak value for strong ground motion and is mainly due to the intensity of the seismic wave. Usually, seismic waves can consist of different characteristics and can have different effects on structures. Therefore, it may be undesirable that the effects of a seismic wave are evaluated only based on the PGA. In this study, time history analysis was executed with a single degree of freedom model for inelastic seismic analysis. The numerical model was assumed to be a perfect elasto-plastic model. Input accelerations were made with El Centro NS (1940), other earthquake records and artificial earthquakes. The displacement ductility demand and cumulative dissipated energy, which were calculated from other artificial earthquakes, were compared. As a result, different responses from other seismic waves which have the same PGA were identified. Therefore, an index which could reflect both seismic and structural characteristics is needed. The SI (Spectrum Intensity) scale which could be obtained from integration by parts of the velocity response spectrum could be an index reflecting the inelastic seismic response of structures. It can be possible to identify from correlation analysis among the SI scale, displacement ductility demand and cumulative dissipated energy that the SI scale is sufficient to be an index for the inelastic response of structures under seismic conditions.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.7_spc
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• pp.425-434
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• 2016

This study investigates important parameters used to determine an effective peak ground acceleration (EPGA) based on the characteristics of response spectra of historical earthquakes occurred at Korean peninsula. EPGAs are very important since they are implemented in the Korean Building Code for the seismic design of new structures. Recently, the Gyeongju earthquakes with the largest magnitude in earthquakes measured at Korea took place and resulted in non-structural and structural damage, which their EPGAs should need to be evaluated. This paper first describes the basic concepts on EPGAs and the EPGAs of the Gyeongju earthquakes are then evaluated and compared according to epicentral distances, site classes and directions of seismic waves. The EPGAs are dependant on normalizing factors and ranges of period on response spectrum constructed with the Gyeongju earthquake records. Using the normalizing factors and the ranges of period determined based on the characteristics of domestic response spectra, this paper draw a conclusion that the EPGAs are estimated to be about 30 % of the measured peak ground accelerations (PGA).

• Structural Engineering and Mechanics
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• v.32 no.4
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• pp.563-581
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• 2009

In this paper, the peak horizontal ground acceleration over the bedrock (PGA) is calculated by a probabilistic seismic hazard assessment (PSHA). For this reason, at first, all the occurred earthquakes in a radius of 200 km of Sanandaj city have been gathered. After elimination of the aftershocks and foreshocks, the main earthquakes were taken into consideration to calculate the seismic parameters (SP) by Kijko (2000) method. The seismotectonic model of the considered region and the seismic sources of the region have been modeled. In this research, Sanandaj and its vicinity has been meshed as an 8 (vertical lines) * 10 (horizontal lines) and the PGA is calculated for each point of the mesh using the logic tree method and the five attenuation relationships (AR) with different weighted coefficient. These calculations have been performed by the Poisson distribution of four hazard levels. Then by using it, four regional maps of the seismic hazard regions have been provided for Sanandaj and its vicinity. The results show that the maximum and minimum value of PGA for the return periods of 75, 225, 475, 2475 years are (0.114, 0.074) (0.157, 0.101), (0.189, 0.121) and (0.266, 0.170), respectively.

• Journal of the Earthquake Engineering Society of Korea
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• v.22 no.3
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• pp.211-217
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• 2018

The Pohang earthquake with a magnitude of 5.4 occurred on November 15, 2018. The epicenter of this earthquake located in south-east region of the Korean peninsula. Since instrumental recording for earthquake ground motions started in Korea, this earthquake caused the largest economic and life losses among past earthquakes. Korea is located in low-to moderate seismic region, so that strong motion records are very limited. Therefore, ground motions recorded during the Pohang earthquake could have valuable geological and seismological information, which are important inputs for seismic design. In this study, ground motions associated by the 2018 Pohang earthquake are generated using the point source model considering domestic geological parameters (magnitude, hypocentral distance, distance-frequency dependent decay parameter, stress drop) and site amplification calculated from ground motion data at each stations. A contour map for peak ground acceleration is constructed for ground motions generated by the Pohang earthquake using the proposed model.

• Earthquakes and Structures
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• v.22 no.1
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• pp.53-64
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• 2022

This study proposes an intelligent semi-active isolation system combining a variable-stiffness control device and ground motion characteristic prediction. To determine the optimal control parameter in real-time, a genetic algorithm (GA)-fuzzy control law was developed in this study. Data on various types of ground motions were collected, and the ground motion characteristics were quantified to derive a near-fault (NF) characteristic ratio by employing an on-site earthquake early warning system. On the basis of the peak ground acceleration (PGA) and the derived NF ratio, a fuzzy inference system (FIS) was developed. The control parameters were optimized using a GA. To support continuity under near-fault and far-field ground motions, the optimal control parameter was linked with the predicted PGA and NF ratio through the FIS. The GA-fuzzy law was then compared with other control laws to verify its effectiveness. The results revealed that the GA-fuzzy control law could reliably predict different ground motion characteristics for real-time control because of the high sensitivity of its control parameter to the ground motion characteristics. Even under near-fault and far-field ground motions, the GA-fuzzy control law outperformed the FPEEA control law in terms of controlling the isolation layer displacement and the superstructure acceleration.

• Journal of the Korean Institute of Gas
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• v.4 no.3 s.11
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• pp.19-25
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• 2000

In order to prevent secondary disaster such as gas explosion which comes after a devastating magnitude earthquake, the seismic monitoring and transmission system for natural gas governor station was developed. To measure ground motions precisely and operate the seismic monitoring system efficiently, the position and method of accelerometer installation were recommended by the analysis of ground noise patterns of governor station. For making a decision on prompt shut-off of gas supplies in the event of a great earthquake, the real-time calculation algorithm of PGA(Peak Ground Acceleration) and SI(Spectrum Intensity) were developed and it has been implemented in the seismic monitoring and transmission system.