• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.10a
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• pp.345-352
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• 1998

Free-field ground motion during earthquake is significantly affected by the local site conditions and the behavior of structure is influenced by ground motion, it is essential to perform the reliable site characterization and to determine the site specific earthquake response. In this study, case study of site specific ground response evaluation was performed at Inchon area. Step by step procedures for site characterization and one-dimensional site response analysis were introduced and the importance of site specific analysis was verified.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1588-1595
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• 2005

In this study, the installation location of accelerometer and accelerograph for dam are investigated in the field to establish of emergency action against dam failure when earthquake occur and to guarantee the results of seismic stability of dams which are analysed with dynamic analysis method during 1999 to 2003 by KOWACO. By a comparative study concerning of domestic and foreign guidelines of seismic strong motion instrumentation for dams, "Guidelines of Seismic Strong-Motion Instrumentation Installation, Operation and Maintenance for Dams" is established to set up the standard of seismic strong-motion instrumentation for dam, are supervised by KOWACO There is some problems in taking a measure of stability of dams when earthquake event occur because the existing seismic strong motion instruments are operated independently. This make difficult to confirm the occurrence of seismic event. For that reason, in this study the plan of unified operation and maintenance system for strong-motion instrument for dams is designed. It will make possible real-time seismic monitoring, data transmission and receiving, giving warning for earthquake, and exchanging data with national seismic network.

• Earthquakes and Structures
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• v.2 no.2
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• pp.171-187
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• 2011

Rational scaling of design earthquake ground motions for tall buildings is essential for safer, risk-based design of tall buildings. This paper provides the structural designers with an insight for more rational scaling based on drift and input energy demands. Since a resonant sinusoidal motion can be an approximate critical excitation to elastic and inelastic structures under the constraint of acceleration or velocity power, a resonant sinusoidal motion with variable period and duration is used as an input wave of the near-field and far-field ground motions. This enables one to understand clearly the relation of the intensity normalization index of ground motion (maximum acceleration, maximum velocity, acceleration power, velocity power) with the response performance (peak interstory drift, total input energy). It is proved that, when the maximum ground velocity is adopted as the normalization index, the maximum interstory drift exhibits a stable property irrespective of the number of stories. It is further shown that, when the velocity power is adopted as the normalization index, the total input energy exhibits a stable property irrespective of the number of stories. It is finally concluded that the former property on peak drift can hold for the practical design response spectrum-compatible ground motions.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.497-504
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• 1998

In the nonlinear dynamic structural analysis, the given ground excitation as an input should be well defined. Because of the lack of recorded accelerograms in Korea, it is required to generate an artificial earthquake by a stochastic model of ground excitation with various dynamic properties rather than recorded accelerograms. It is well own that earthquake motions are generally non-stationary with time-varying intensity and frequency content. Many researchers have proposed non-stationary random process models. Yeh and Wen (1990) proposed a non-stationary stochastic process model which can be modeled as components with an intensity function, a frequency modulation function and a power spectral density function to describe such non-stationary characteristics. This model is based on the simulation for the strong-motion earthquakes with magnitude greater than approximately 5.0~6.0, because it will be not only expected to cause structural damage but also involved the characteristics of earthquake motions. Also, the recorded earthquake motion within this range are still very scarce in Korea. Thus, it is necessary to verify the model by the application of it to the mid-magnitude (approximately 4.0~6.0) earthquakes actually recorded in domestic or foreign area. The purpose of the paper is to generate an artificial earthquake using the model of Yeh and Wen in the area with low seismicity.

• Earthquakes and Structures
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• v.16 no.4
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• pp.487-499
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• 2019

Energy-based seismic design of structures has gradually become prominent in today's structural engineering investigations because of being more rational and reliable when it is compared to traditional force-based and displacement-based methods. Energy-based approaches have widely taken place in many previous studies and investigations and undoubtedly, they are going to play more important role in future seismic design codes, too. This paper aims to compute the maximum earthquake energy input to elastic single-degree-of-freedom (SDOF) systems for selected real ground motion records. A data set containing 100 real ground motion records which have the same site soil profiles has been selected from Pacific Earthquake Research (PEER) database. Response time history (RTH) analyses have been conducted for elastic SDOF systems having a constant damping ratio and natural periods of 0.1 s to 3.0 s. Totally 3000 RTH analyses have been performed and the maximum mass normalized earthquake input energy values for all records have been computed. Previous researchers' approaches have been compared to the results of RTH analyses and an approach which considers the pseudo-spectral velocity with Arias Intensity has been proposed. Graphs of the maximum earthquake input energy versus the maximum pseudo-spectral velocity have been obtained. The results show that there is a good agreement between the maximum input energy demands of RTH analysis and the other approaches and the maximum earthquake input energy is a relatively stable response parameter to be used for further seismic design and evaluations.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.18-25
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• 2005

Stochastic ground-motion method is adopted to simulate horizontal PGA values for the offshore Uljin earthquake recorded at nationwide seismic stations. For this purpose, the Fourier spectra are calculated at every stations based on comprehensive results of wave propagation and site effect which were previously revealed through inversion process applied to large accumulated spectral D/B. In addition, the apparent source spectrum of the offshore Uljin earthquake is estimated by removing the path and site response from the observed spectra. The distance dependent time-duration model is revised by iteratively fitting the PGA values generated by using the raw spectra data to the observed PGA data. The stochastic ground-motion method predicts the observed PGA values within a error of ${\sigma}_{log10}=0.1$. Transfer functions of a site relative to another site are estimated based on the error residual of the inversion results and used to convert PGA values at multiple stations to expected PGA values at a reference station of TJN. The converted PGA values can be used as basic data to evaluate the ground-motion attenuation relations developed for seismic hazard analysis that concerns the large damaging earthquakes.

• Earthquakes and Structures
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• v.9 no.5
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• pp.1091-1114
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• 2015

The adequacy of a number of advanced earthquake Intensity Measures (IMs) to predict the structural damage of earthquake resistant 3D R/C buildings is investigated in the present paper. To achieve this purpose three symmetric in plan and three asymmetric 5-storey R/C buildings are analyzed by nonlinear time history analysis using 74 bidirectional earthquake records. The two horizontal accelerograms of each ground motion are applied along the structural axes of the buildings and the structural damage is expressed in terms of the maximum and average interstorey drift as well as the overall structural damage index. For each individual pair of accelerograms the values of the aforementioned seismic damage measures are determined. Then, they are correlated with several strong motion scalar IMs that take into account both earthquake and structural characteristics. The research identified certain IMs which exhibit strong correlation with the seismic damage measures of the studied buildings. However, the degree of correlation between IMs and the seismic damage depends on the damage measure adopted. Furthermore, it is confirmed that the widely used spectral acceleration at the fundamental period of the structure is a relatively good IM for medium rise R/C buildings that possess small structural eccentricity.

• Earthquakes and Structures
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• v.8 no.6
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• pp.1481-1497
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• 2015

Vertical earthquake ground motion may magnify vertical dynamic responses of structures, and thus cause serious damage to bridges. As main support structures, piers and bearings play an important role in vertical seismic response analysis of girder bridges. In this study, the pier and bearing are simplified as a vertical series spring system without mass. Then, based on the assumption of small displacement, the equation of motion governing the simply-supported straight girder bridge under vertical ground motion is established including effects of vertical deformation of support structures. Considering boundary conditions, the differential quadrature method (DQM) is applied to discretize the above equation of motion into a MDOF (multi-degree-of-freedom) system. Then seismic responses of this MDOF system are calculated by a step-by-step integration method. Effects of support structures on vertical dynamic responses of girder bridges are studied under different vertical strong earthquake motions. Results indicate that support structures may remarkably increase or decrease vertical seismic responses of girder bridges. So it is of great importance to consider effects of support structures in structural seismic design of girder bridges in near-fault region. Finally, optimization of support structures to resist vertical strong earthquake motions is discussed.

• Journal of the Earthquake Engineering Society of Korea
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• v.25 no.1
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• pp.33-42
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• 2021

The design response spectrum presented in the seismic design standard reflects the characteristics of the tectonic environment at a site. However, since the design response spectrum does not represent the ground motion with a specific earthquake magnitude or distance, input ground motions for response history analysis need to be selected reasonably. It is appropriate to use observed ground motions recorded in Korea for the seismic design. However, recently recorded ground motions in the Gyeongju (2016) or Pohang (2017) earthquakes are not compatible with the design response spectrum. Therefore, it is necessary to convert the recorded ground motion in Korea to a model similar to the design response spectrum. In this study, several approaches to adjust the spectral acceleration level at each period range were tested. These are the intrinsic and scattering attenuation considering the earthquake environment, magnitude, distance change by the green function method, and a rupture propagation direction's directivity effect. Using these variables, the amplification ratio for the representative natural period was regressed. Finally, the optimum condition compatible with the design response spectrum was suggested, and the validation was performed by converting the recorded ground motion.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1997.04a
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• pp.128-135
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• 1997

The indirect boundary integral equation is formulated to analyze the behavior of a cavity in a multilayered half-plane subjected to earthquake waves. This formulation uses the fundamental solutions that are numerically calculated by the generalized transmission and reflection coefficient method. The free surface of the cavity without external excitation influences the behavior of the half-plane. Consequently this analysis adds the consideration of scattering-field into the analysis and the total motion field of the cavity is decomposed into the free-field and scattering-field motions. The free-field motion is obtained from the modification of the transmission and reflection coefficient method. The scattering-field motion is calculated is calculated by the indirect boundary value problem which has the ficticious boundaries and sources. In this study, P wave, SV wave, SH wave, and Rayleigh wave are analyzed respectively.