• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.767-772
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• 2002

Free-field ground motion during earthquake is significantly affected by the local site conditions and it is essential in the seismic design to perform the accurate site-specific ground response analysis. In this paper, one-dimensional seismic characteristics of waste landfill are studied based on the vertical propagation of horizontal shear waves through the column of soil/waste. Seismic response analysis is peformed for short-period, long-period and artificial earthquake ground motions using a computer program for seismic response analysis of horizontally layered soil deposits. The computed peak ground accelerations are compared with the values calculated according to Korean seismic design guidelines. The analysis result shows that the long-period earthquake causes the largest peak ground acceleration while the artificial earthquake results in the smallest one.

• Journal of the Earthquake Engineering Society of Korea
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• v.17 no.6
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• pp.279-291
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• 2013

The seismic damage of non-structural components, such as communication facilities, causes direct economic losses as well as indirect losses which result from social chaos occurring with downtime of communication and financial management network systems. The current Korean seismic code, KBC2009, prescribes the design criteria and requirements of non-structural components based on their elastic response. However, it is difficult for KBC to reflect the dynamic characteristics of structures where non-structural components exist. In this study, both linear and nonlinear time history analyses of structures with various analysis parameters were carried out and floor acceleration spectra obtained from analyses were compared with both ground acceleration spectra used for input records of the analyses and the design floor acceleration spectrum proposed by National Radio Research Agency. Also, this study investigates to find out the influence of structural dynamic characteristics on the floor acceleration spectra. The analysis results show that the acceleration amplification is observed due to the resonance phenomenon and such amplification increases with the increase of building heights and with the decrease of structure's energy dissipation capacities.

• 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.

• Structural Engineering and Mechanics
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• v.69 no.3
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• pp.293-306
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• 2019

In current seismic design codes, various elastic design acceleration spectra are defined considering different seismological and soil characteristics and are widely used tool for calculation of seismic loads acting on structures. Response spectrum analyses directly use the elastic design acceleration spectra whereas time history analyses use acceleration records of earthquakes whose acceleration spectra fit the design spectra of seismic codes. Due to the fact that obtaining coherent structural response quantities with the seismic design code considerations is a desired circumstance in dynamic analyses, the response spectra of earthquake records used in time history analyses had better fit to the design acceleration spectra of seismic codes. This paper evaluates structural response distributions of multi-story reinforced concrete frames obtained from nonlinear time history analyses which are performed by using the scaled earthquake records compatible with various elastic design spectra. Time domain scaling procedure is used while processing the response spectrum of real accelerograms to fit the design acceleration spectra. The elastic acceleration design spectra of Turkish Seismic Design Code 2007, Uniform Building Code 1997 and Eurocode 8 are considered as target spectra in the scaling procedure. Soil classes in different seismic codes are appropriately matched up with each other according to $V_{S30}$ values. The maximum roof displacements and the total base shears of considered frame structures are determined from nonlinear time history analyses using the scaled earthquake records and the results are presented by graphs and tables. Coherent structural response quantities reflecting the influence of elastic design spectra of various seismic codes are obtained.

• Earthquakes and Structures
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• v.4 no.5
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• pp.557-585
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• 2013

The recent huge earthquake ground motion records in Japan result in the reconsideration of seismic design forces for nuclear power stations from the view point of seismological research. In addition, the seismic design force should be defined also from the view point of structural engineering. In this paper it is shown that one of the occurrence mechanisms of such large acceleration in recent seismic records (recorded in or near massive structures and not free-field ground motions) is due to the interaction between a massive building and its surrounding soil which induces amplification of local mode in the surface soil. Furthermore on-site investigation after earthquakes in the nuclear power stations reveals some damages of soil around the building (cracks, settlement and sand boiling). The influence of plastic behavior of soil is investigated in the context of interaction between the structure and the surrounding soil. Moreover the amplification property of the surface soil is investigated from the seismic records of the Suruga-gulf earthquake in 2009 and the 2011 off the Pacific coast of Tohoku earthquake in 2011. Two methods are introduced for the analysis of the non-stationary process of ground motions. It is shown that the non-stationary Fourier spectra can detect the temporal change of frequency contents of ground motions and the displacement profile integrated from its acceleration profile is useful to evaluate the seismic behavior of the building and the surrounding soil.

• Journal of the Earthquake Engineering Society of Korea
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• v.22 no.5
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• pp.261-269
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• 2018

This study examines earthquake-induced sloshing effects on liquid storage tanks using computation fluid dynamics. To achieve this goal, this study selects an existing square steel tank tested by Seismic Simulation Test Center at Pusan National University as a case study. The model validation was firstly performed through the comparison of shaking table test data and simulated results for the water tank subjected to a harmonic excitation. For a realistic estimation of the wall pressure response of the water tank, three recorded earthquakes with similar peak ground acceleration are applied:1940 El Centro earthquake, 2016 Gyeongju earthquake, and 2017 Pohang earthquake. Wall pressures monitored during the dynamic analyses are examined and compared for different earthquake motions and monitoring points, using power spectrum density. Finally, the maximum dynamic pressure for three earthquakes is compared with the design pressure calculated from a seismic design code. Results indicated that the maximum pressure from the El Centro earthquake exceeds the design pressure although its peak ground acceleration is less than 0.4 g, which is the design acceleration. On the other hand, the maximum pressure due to two Korean earthquakes does not reach the design pressure. Thus, engineers should not consider only the peak ground acceleration when determining the design pressure of water tanks.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.2
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• pp.35-44
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• 1998

Because of the continual occurrence of minor and moderate earthquakes in Korean peninsula, it is generally considered that Korean is not located in a safe region against probable earthquake any more, even though being recognized as a safe country in earthquake. It is in particular noted that nowadays there has been much concern about unexpected tragedy due to probable earthquake since the disaster of 1995 kobe earthquake. Thus, the objective of this research is to develop appropriate design spectrum which could be practicably used in seismic design of important structures taking into consideration of local physical characteristics. Particularly, we have to keep in mind the lessons from 1985 Mexico earthquake which had disregarded deep research on local ground conditions, being a possible magnification phenomena of ground motions in weak soil layer. Various spectra has been described based on the analysis of historical earthquakes, and generate the artificial ground acceleration. Also, rational numbers of artificial ground acceleration is investigated by the seismic analysis for skew slab bridges.

• 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.

• Earthquakes and Structures
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• v.3 no.1
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• pp.59-81
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• 2012

A ductility inverse-mapping method for SDOF systems including passive dampers is proposed which enables one to find the maximum acceleration of ground motion for the prescribed maximum response deformation. In the conventional capacity spectrum method, the maximum response deformation is computed through iterative procedures for the prescribed maximum acceleration of ground motion. This is because the equivalent linear model for response evaluation is described in terms of unknown maximum deformation. While successive calculations are needed, no numerically unstable iterative procedure is required in the proposed method. This ductility inverse-mapping method is applied to an SDOF model of bilinear hysteresis. The SDOF models without and with passive dampers (viscous, viscoelastic and hysteretic dampers) are taken into account to investigate the effectiveness of passive dampers for seismic retrofitting of building structures. Since the maximum response deformation is the principal parameter and specified sequentially, the proposed ductility inverse-mapping method is suitable for the implementation of the performance-based design.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.487-494
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• 2005

In this study, a set of artificial earthquake time histories, which can be used for the earthquake-resistant design of seismically isolated highway bridges, was presented. In addition, adequateness of the generated ground accelerations was investigated. These were performed based on the seismic design standard for seismically isolated bridges. Total of 22 acceleration time histories were generated for each soil condition by the spectral method. The time histories were verified to meet the code provisions including (1) mean response spectrum at control frequencies, (2) EPGA (effective peak ground acceleration), and (3) correlation coefficient. Finally, the maximum response corresponding to four time histories and the mean response associated with seven time histories were computed using the generated acceleration time histories, which shows validity of the proposed artificial earthquake time histories.