• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.707-714
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• 2009

The design response spectrum generally used in Korea is decided by the site coefficients determined by deterministic methodology, while it is based on probabilistic seismic hazard analysis. The design response spectrum has to be made using probabilistic method which includes uncertainties of ground motions and ground properties for coincide with probabilistic methodology of seismic hazard analysis. In this study probabilistic site coefficients were developed, which were defined by the results of site response analysis using a set of ground motion that was compatible with present seismic hazard map. The design response spectrum defined by probabilistic seismic coefficients resulted in lower spectrum in long period area and larger spectrum in short period area. Also, the maximum spectral accelerations in site class D and site class E were lower than one in site class C while in the previous design response spectrum the maximum spectral acceleration increased from site class A to E.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.113-124
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• 2006

Despite the site classification method was improved in the previous study, the response spectrum would be required to be modified by adjusting the integration interval to calculate the site coefficients because the response spectra did not match well the average spectral accelerations obtained by site response analyses in the range of long periods. In this paper, new response spectra for each site categories were determined by adjusting the integration interval of long-period site coefficient $F_{v}$ from $0.4{\sim}2.0$ to $0.4{\sim}1.5$ second. It matched well the average spectral accelerations and new response spectrum, and it was also improved compared to the current site classification system.

• Ocean Systems Engineering
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• v.8 no.3
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• pp.281-312
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• 2018

Characteristics of a turbulence wind model control the magnitude and frequency distribution of wind loading on floating offshore wind turbines (FOWTs), and an in-depth understanding of how wind spectral characteristics affect the responses, and ultimately the design cost of system components, is in shortage in the offshore wind industry. Wind spectrum models as well as turbulence intensity curves recommended by the International Electrotechnical Commission (IEC) have characteristics derived from land-based sites, and have been widely adopted in offshore wind projects (in the absence of site-specific offshore data) without sufficient assessment of design implications. In this paper, effects of wind spectra and turbulence intensities on the strength or extreme responses of a 5 MW floating offshore wind turbine are investigated. The impact of different wind spectral parameters on the extreme blade loads, nacelle accelerations, towertop motions, towerbase loads, platform motions and accelerations, and mooring line tensions are presented and discussed. Results highlight the need to consider the appropriateness of a wind spectral model implemented in the strength design of FOWT structures.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.141-148
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• 2006

This study describes a generation of artificial earthquake wane compatible with seismic design spectrum. In seismic response analysis of building structures, the input ground accelerations have considerable effect on dynamic characteristics of structures. Therefore, it is important to properly select input ground motions for seismic response analysis. In this paper, the artificial earthquake wave are generated according to previously recorded earthquake waves in past earthquake events. The artificial wave have identical phase angles to the recorded earthquake wane, and their overall response spectra are compatible with seismic design spectrum with 5% of critical viscous damping. Each simulated earthquake wave has a identical phase angles to the original recorded ground acceleration, and match to design response spectra in the range of period from 0.02 to 10.0 seconds. It is concluded that the artificial earthquake waves simulated in this paper ate applicable as input ground motions for a seismic response analysis of building structures.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.7_spc
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• pp.527-536
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• 2016

This paper investigates seismic damage potential of recent September 12 M5.8 Gyeongju earthquake from diverse earthquake engineering perspectives using the accelerograms recorded at three stations near the epicenter. In time domain, strong motion durations are evaluated based on the accelerograms and compared with statistical averages of the ground motions with similar magnitude, epicentral distance and soil conditions, while Fourier analysis using FFT is performed to identify damaging frequency contents contained in the earthquake. Effective peak ground accelerations are evaluated from the calculated response spectra and compared with apparent peak ground accelerations and the design spectrum in KBC 2016. All these results are used to consistently explain the reason why most of seismic damage in the earthquake was concentrated on low-rise stiff buildings but not quite significant. In order to comparatively appraise the damage potential, the constant ductility spectrum constructed from the Gyeongju earthquake is compared with that of the well-known 1940 El Centro earthquake. Deconvolution analysis by using one accelerogram speculated to be recorded at a stiff soil site is also performed to estimate the soil profile conforming to the response spectrum characteristics. Finally, response history analysis for 39- and 61-story tall buildings is performed as a case study to explain significant building vibration felt on the upper floors of some tall buildings in Busan area during the Gyeongju earthquake. Seismic design and retrofit implications of M5.8 Gyeongju earthquake are summarized for further research efforts and improvements of relevant practice.

• Fire Science and Engineering
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• v.22 no.1
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• pp.10-15
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• 2008

In this study, seismic design in sprinkler head pipeline of water extinguishing system has been carried out. This study describes a generation of artificial earthquake wave compatible with seismic design spectrum, and also analyzed the dynamic response spectra by the simulated earthquake motion. This study constructed powerful engineering base for seismic design, and presented seismic design techniques of water and gas extinguishing piping system. Also, this study readied basis that can apply seismic design and performance estimation of fire fighting system and performance rating as well as pipeline of water extinguishing system from result of this research. Hereafter, if additional research by earthquake magnitude and ground kind is approached, reliance elevation, safety raising and performance based design of fire fighting system see to achieve.

• 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.26 no.6
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• pp.687-707
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• 2007

High-tech facilities engaged in the production of semiconductors and optical microscopes are extremely expensive, which may require time-domain analysis for seismic resistant design in consideration of the most critical directions of seismic ground motions. This paper presents a framework for generating three-dimensional critical seismic ground acceleration time histories compatible with the response spectra specified in seismic design codes. The most critical directions of seismic ground motions associated with the maximum response of a high-tech facility are first identified. A new numerical method is then proposed to derive the power spectrum density functions of ground accelerations which are compatible with the response spectra specified in seismic design codes in critical directions. The ground acceleration time histories for the high-tech facility along the structural axes are generated by applying the spectral representation method to the power spectrum density function matrix and then multiplied by envelope functions to consider nonstationarity of ground motions. The proposed framework is finally applied to a typical three-story high-tech facility, and the numerical results demonstrate the feasibility of the proposed approach.

• Earthquakes and Structures
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• v.3 no.3_4
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• pp.549-561
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• 2012

Many building foundations are embedded, however it is not easy to compact the backfill around the foundation especially for the deeply embedded ones. The soil condition around the embedded foundation may affect the seismic response of a building due to the weak contact between the soil and the foundation. In this paper, the response accelerations in the short-period range and at the period of 1 second (in the long-period range) for a seismic design spectrum specified in the IBC design code were compared considering perfect and poor backfills to investigate the effect of backfill compaction around the embedded foundation. An in-house finite-element software (P3DASS) which has the capability of horizontal pseudo-3D seismic analysis with linear soil layers was used to perform the seismic analyses of the structure-soil system with an embedded foundation. Seismic analyses were carried out with 7 bedrock earthquake records provided by the Pacific Earthquake Engineering Research Center (PEER), scaling the peak ground accelerations to 0.1 g. The results indicate that the poor backfill is not detrimental to the seismic response of a building, if the foundation is not embedded deeply in the soft soil. However, it is necessary to perform the seismic analysis for the structure-soil system embedded deeply in the soft soil to check the seismic resonance due to the soft soil layer beneath the foundation, and to compact the backfill as well as possible.

• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.5
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• pp.269-277
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• 2019

In a seismic design, a structural demand by an earthquake load is determined by design response spectra. The ground motion is a three-dimensional movement; therefore, the design response spectra in each direction need to be assigned. However, in most design codes, an identical design response spectrum is used in two horizontal directions. Unlike these design criteria, a realistic seismic input motion should be applied for a seismic evaluation of structures. In this study, the definition of horizontal spectral acceleration representing the two-horizontal spectral acceleration is reviewed. Based on these methodologies, the horizontal responses of observed ground motions are calculated. The data used in the analysis are recorded accelerograms at the stations near the epicenters of recent earthquakes which are the 2007 Odeasan earthquake, 2016 Gyeongju earthquake, and 2017 Pohang earthquake. Geometric mean-based horizontal response spectra and maximum directional response spectrum are evaluated and their differences are compared over the period range. Statistical representation of the relations between geometric mean and maximum directional spectral acceleration for horizontal direction and spectral acceleration for vertical direction are also evaluated. Finally, discussions and suggestions to consider these different two horizontal directional spectral accelerations in the seismic performance evaluation are presented.