• Geomechanics and Engineering
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• v.13 no.3
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• pp.411-429
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• 2017

A Spectral Element Method for 3D seismic wave propagation simulation is derived based on the three-dimensional fluctuating elastic dynamic equation. Considering the 3D real terrain and the attenuation characteristics of the medium, the topographic effect of Wenchuan earthquake is simulated by using the Spectral Element Method (SEM) algorithm and the ASTER DEM model. Results show that the high PGA (peak ground acceleration) region was distributed along the peak and the slope side away from the epicenter in the epicenter area. The overall distribution direction of high PGA and high PGV (peak ground velocity) region is parallel to the direction of the seismogenic fault. In the epicenter of the earthquake, the ground motion is to some extent amplified under the influence of the terrain. The amplification effect of the terrain on PGA is complicated. It does not exactly lead to amplification of PGA at the ridge and the summit or attenuation of PGA in the valley.

• Geomechanics and Engineering
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• v.9 no.2
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• pp.125-144
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• 2015

This paper presents the probabilistic seismic microzonation of densely populated Kolkata city, situated on the world's largest delta island with very soft alluvial soil deposit. At first probabilistic seismic hazard analysis of Kolkata city was carried out at bedrock level and then ground motion amplification due to sedimentary deposit was computed using one dimensional (1D) wave propagation analysis SHAKE2000. Different maps like fundamental frequency, amplification at fundamental frequency, peak ground acceleration (PGA), peak ground velocity (PGV), peak ground displacement (PGD), maximum response spectral acceleration at different time period bands are developed for variety of end users, structural and geotechnical engineers, land use planners, emergency managers and awareness of general public. The probabilistically predicted PGA at bedrock level is 0.12 g for 50% exceedance in 50 years and maximum PGA at surface level it varies from 0.095 g to 0.18 g for same probability of exceedance. The scenario of simulated ground motion revealed that Kolkata city is very much prone to damage during earthquake.

• Journal of the Korean earth science society
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• v.37 no.1
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• pp.52-61
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• 2016

The purpose of the study was to create a probabilistic seismic hazard map using the input data that reflected the seismo-tectonic characteristics of the Korean Peninsula by applying USGS program (Harmsen (2008). The program was partly modified for the purpose of this study. The uncertainty of input parameters given by specialists was reflected in calculating the seismic hazard values by logic tree method. The general pattern of PGA was quite sensitive and similar to the shape of areal source. The probabilistic seismic hazard map showed the contour distribution of peak acceleration (%g) with 10% probability of exceedance in 5, 10, 20, 50, 100, 250, and 500 years. The result showed that the peak ground acceleration (PGA) values of the northern peninsula were almost half values of the southern peninsula except Hwanghae province. The general trend of the hazard map extended in the direction of NW-SE from Whanghae province to south-eastern regions of the peninsula. The values in northern part of Kangwon province were relatively lower than other areas in the southern peninsula. The maps produced through this study are considered valuable in regulating the seismic safety of the major facilities in the Korean Peninsula.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.581-586
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• 1997

The objective of this study is to investigate the behavior of a 1/5-scale 3-story nonductile reinforced concrete frame subjected to earthquake excitation. For this purpose, Taft N21E earthquake accelerogram was simulated by using 3m${\times}$5m shaking table. When the input acceleration is compared to that of output, it can be found that simulation of shaking table is excellent. From the results of test with Taft N21E earthquake accelerogram adjusted to peak ground acceleration(PGA) 0.06g and 0.12g(maximum acceleration in korea seismic code) the model responded in elastic behavior and it is found that the existing building in our country are safe against the levels of PGA 0.06g and 0.12g.

• Journal of the Korean Geotechnical Society
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• v.35 no.12
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• pp.135-145
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• 2019

The slope collapse can be classified into internal and external factors. Internal factors are engineering factors inherent in the formation of slopes such as soil depth, slope angle, shear strength of soil, and external factors are external loading such as earthquakes. The external factor for earthquake can be expressed by various values such as peak ground acceleration (PGA), peak ground velocity (PGV), Arias coefficient (I), natural period (T_p), and spectral acceleration (S_aT=1.0). Specially, PGA is the most typical value that defines the magnitude of the ground motion of an earthquake. However, it is not enough to consider the displacement in the slope which depends on the duration of the earthquake even if the vibration has the same peak ground acceleration. In this study, numerical analysis of two-dimensional plane strain conditions was performed on engineered block, and slope responses due to seismic motion of scaling PGA to 0.2 g various event scenarios was analyzed. As a result, the response of slope is different depending on the presence or absence of sliding block; it is shown that slope response depend on the seismic wave triggering sliding block than the input motion factors.

• Geomechanics and Engineering
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• v.4 no.1
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• pp.1-18
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• 2012

The spatial variation of ground motion in Kolkata Metropolitan District (KMD) has been estimated by generating synthetic ground motion considering the point source model coupled with site response analysis. The most vulnerable source was identified from regional seismotectonic map for an area of about 350 km radius around Kolkata. The rock level acceleration time histories at 121 borehole locations in Kolkata for the vulnerable source, Eocene Hinge Zone, due to maximum credible earthquake (MCE) moment magnitude 6.2 were generated by synthetic ground motion model. Soil investigation data of 121 boreholes were collected from the report of Soil Data Bank Project, Jadavpur University, Kolkata. Surface level ground motion parameters were determined using SHAKE2000 software. The results are presented in the form of peak ground acceleration (PGA) at rock level and ground surface, amplification factor, and the response spectra at the ground surface for frequency 1.5 Hz, 3 Hz, 5 Hz and 10 Hz and 5% damping ratio. Site response study shows higher PGA in comparison with rock level acceleration. Maximum amplification in some portion in KMD area is found to be as high as 3.0 times compared to rock level.

• The Journal of Engineering Geology
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• v.33 no.2
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• pp.293-305
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• 2023

Three ground models are analyzed using a 1g shaking table and laminar shear box (LSB) to investigate the impact of the ground structure on seismic wave amplification during earthquakes. Multi-layer horizontal, embankment, and basin ground models are selected for this investigation, with each model being divided into dense and loose ground layers, Accelerometers are installed during the construction of each ground model to capture any seismic wave amplification owing th the propagation of an artificial seismic wave, sine wave sweep, and 10-Hz sine wave through a given ground model. The amplification of the tested seismic waves is analyzed using the observed peak ground acceleration and spectrum acceleration. The observed acceleration amplification in the multi-layer horizontal ground model is significantly higher the seismic waves that propagated across the dense ground-loose ground boundary compared with those that only propagated through the dense ground. Furthermore, the observed acceleration amplification gradually increases in the central part of the multi-layer embankment and basin models for the seismic waves that propagated across the dense ground-loose ground boundary.

• Journal of the Korean Geotechnical Society
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• v.36 no.11
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• pp.21-33
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• 2020

Ground response analysis has been conducted for each borehole data in Pohang area, using 1D equivalent linear method program, to investigate the applicability of amplification factor to estimate peak ground acceleration. Earthquake motions for ground response analysis were prepared by matching response spectrums for return period of 500, 1000, and 2400 years suggested by seismic design code (MOIS, 2017). Ground survey data were acquired from Geotechnical Information DB System. It has been confirmed that response spectrum obtained from ground response analysis showed good agreement with those from seismic design code irrespective of ground classification. However, PGA (Peak Ground Accelerations) of ground response analysis did not coincide with PGA calculated using amplification factor suggested by seismic design code.

• Earthquakes and Structures
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• v.24 no.6
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• pp.455-475
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• 2023

The present study investigates the non-linear soil-pile interaction using three-dimensional (3D) non-linear finite element models. The numerical models were validated by using the results of extensive pile load and shaking table tests. The pile performance in liquefiable and non-liquefiable soil has been studied by analyzing the liquefaction ratio, pile lateral displacement (LD), pile bending moment (BM), and frictional resistance (FR) results. The pile models have been developed for the different ground conditions. The study reveals that the results obtained during the pile load test and shaking cycles have good agreement with the predicted pile and soil response. The soil density, peak ground acceleration (PGA), slenderness ratio (L/D), and soil condition (i.e., dry and saturated) are considered during modeling. Four ground motions are used for the non-linear time history analyses. Consequently, design charts are proposed depended on the analysis results to be used for design practice. Eleven models have been used to validate the capability of these charts to capture the soil-pile response under different seismic intensities. The results of the present study demonstrate that L/D ratio slightly affects the lateral displacement when compared with other parameters. Also, it has been observed that the increasing in PGA and decreasing L/D decreases the excess pore water pressure ratio; i.e., increasing PGA from 0.1 g to 0.82 g of loose sand model, decrease the liquefaction ratio by about 50%, and increasing L/D from 15 to 75 of the similar models (under Kobe earthquake), increase this ratio by about 30%. This study reveals that the lateral displacement increases nonlinearly under both dry and saturated conditions as the PGA increases. Similarly, it is observed that the BM increases under both dry and saturated states as the L/D ratio increases. Regarding the acceleration histories, the pile BM was reduced by reducing the acceleration intensity. Hence, the pile BM decreased to about 31% when the applied ground motion switched from Kobe (PGA=0.82 g) to Ali Algharbi (PGA=0.10 g). This study reveals that the soil conditions affect the relationship pattern between the FR and the PGA. Also, this research could be helpful in understanding the threat of earthquakes in different ground characteristics.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.1
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• pp.41-48
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• 2024

In 2017, the Ministry of the Interior and Safety conducted research for the revision of seismic design standards and performed studies on standard design response spectra. As a result, the Common Application Guidelines for Seismic Design Standards were introduced, and these guidelines have been implemented in the national design standards of the Ministry of Land, Infrastructure, and Transport for practical use. However, it should be noted that the research for proposing standard design response spectra during the 2017 revision was conducted before the occurrence of the significant seismic events in South Korea, such as the 2016 Gyeongju Earthquake and the 2017 Pohang Earthquake. To account for these recent major earthquakes, this study adjusted the standard design spectra based on the records of the 2016 Gyeongju Earthquake and the 2017 Pohang Earthquake and conducted ground response analyses accordingly. The results revealed variations in peak ground acceleration (PGA) at the ground surface even within the same ground classification. It was confirmed that this variation can lead to overestimation or underestimation of seismic loads.