• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.4
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• pp.759-768
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• 2015

The ground motions of large dimensional structures such as long span bridges at different stations during an earthquake, are inevitably different, which is known as the ground motion spatial variation effect. There are many causes that may result in the spatial variability in seismic ground motion, e.g., the wave passage effect due to the different arrival times of waves at different locations; the loss of coherency due to seismic waves scattering in the heterogeneous medium of the ground; the site amplification effect owing to different local soil properties. In previous researches, the site amplification effects have not been considered or considered by a single-layered soil model only. In this study, however, the ground motion amplification and filtering effects are evaluated by multi-layered soil model. Spatially varying ground motion at the sites with different number of layers, depths, and soil characteristics are generated and the variation characteristics of ground motion time histories according to the correlation of coherency loss function and soil conditions are evaluated. For the bridge system composed of two unit bridges, seismic behavior characteristics are analyzed using the generated seismic waves as input ground motion. Especially, relative displacement due to coherency loss and site effect which can cause the unseating and pounding between girders are evaluated. As a result, considering the soil conditions of each site are always important and should not be neglected for an accurate structural response analysis.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.5 s.51
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• pp.11-23
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• 2006

This paper evaluates the seismic response of multi-span prestressed concrete girder bridges typically found in the New Madrid Seismic Zone region of the central United States. Using detailed nonlinear analytical models and synthetic ground motion records for Memphis, TN, nonlinear response history analyses are performed for two levels of ground motion: 10% probability of exceedance (PE) in 50 years, and 2% probability of exceedance (PE) in 50 years. The results show that the bridge performance is very good fur the 10% PE in 50 years ground motion level. However, the performance for the 2% PE in 50 years ground motion is not so good because it results in highly inelastic behavior of the bridge. Impact between decks results in large ductility demands on the columns, and failure of the bearings that support the girders. It is found that making the superstructure continuous, which is commonly performed for reducing dead load moments and maintenance requirements, results in significant improvement in the seismic response of prestressed concrete girder bridges.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.137-144
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• 2019

For the structures near the seismogenic fault, the evaluation of seismic performance against near-fault ground motions is important as well as for design ground motions. In this study, characteristics of seismic behaviors and seismic performance of the pile-bent bridge constructed on the thick soft soil site with various weak soil layers were analyzed. The input ground motions were synthesized by the directivity pulse parameters for intra-plate regions. The ground motion acceleration histories of each layer were obtained by one-dimensional site response analysis. Each soil layer was modeled by equivalent linear springs, and multi-support excitations with different input ground motions at each soil spring were applied for nonlinear seismic analyses. The analysis result by the near-fault ground motions and ground motions matched to design spectra were compared. In case of the near fault ground motion input, the bridge behaved within the elastic range but the location of the maximum moment occurred was different from the result of design ground motion input.

• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.5
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• pp.181-190
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• 2022

In assessing the seismic safety of nuclear power plants, it is essential to analyze the structures using the observed ground motion. In particular, spatial variation in which the characteristics of the ground motion record differ may occur if the location is different within the site and even if the same earthquake is experienced. This study analyzed the spatial variation characteristics of the ground motion observed at the structure and site using the earthquake records measured at the Hamaoka nuclear power plant. Even if they were located on the same floor within the same unit, there was a difference in response depending on the location. In addition, amplification was observed in Unit 5 compared to other units, which was due to the rock layer having a slower shear wave velocity than the surrounding bedrock. Significant differences were also found in the records of the structure's foundation and the free-field surface. Based on these results, the necessity of considering spatial variation in the observed records was suggested.

• Structural Engineering and Mechanics
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• v.21 no.1
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• pp.83-100
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• 2005

This paper presents results from a study to extend a performance-based shearwall selection procedure to take into account the contributions of nonstructural finish materials (such as stucco and gypsum wallboard), construction quality issues, and their effects on the displacement performance of engineered wood shearwalls subject to seismic loading. Shearwall performance is evaluated in terms of peak displacements under seismic loading (characterized by a suite of ordinary ground motion records) considering different combinations of performance levels (drift limits) and seismic hazard. Shearwalls are analyzed using nonlinear dynamic time-history analysis with global assembly hysteretic parameters determined by fitting to actual shearwall test data. Peak displacement distributions, determined from sets of analyses using each of the ground motion records taken to characterize the seismic hazard, are postprocessed into performance curves, design charts, and fragility curves which can be used for risk-based design and assessment applications.

• Earthquakes and Structures
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• v.15 no.6
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• pp.605-616
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• 2018

In this paper, an extended Cloud analysis method is developed for seismic fragility assessment of existing highway bridges in the southeast Queensland region. This method extends the original Cloud analysis dataset by performing scaled Cloud analyses. The original and scaled Cloud datasets are then paired to generate seismic fragility curves. The seismic hazard in this region is critically reviewed, and the ground motion records are selected for the time-history analysis based on various record selection criteria. A parametric highway bridge model is developed in the OpenSees analysis software, and a sampling technique is employed to quantify the uncertainties of highway bridges ubiquitous in this region. Technical recommendations are also given for the seismic performance evaluation of highway bridges in such low-to-moderate seismic zones. Finally, a probabilistic fragility study is conducted by performing a total of 8000 time-history analyses and representative bridge fragility curves are generated. It is illustrated that the seismic fragility curves generated by the proposed extended Cloud analysis method are in close agreement with those which are obtained by the rigorous incremental dynamic analysis method. Also, it reveals that more than 50% of highway bridges existing in southeast Queensland will be damaged subject to a peak ground acceleration of 0.14 g.

• Nuclear Engineering and Technology
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• v.52 no.1
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• pp.192-205
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• 2020

Seismic design practices and seismic response analyses of civil structures and nuclear power plants (NPPs) have conventionally used the peak ground acceleration (PGA) or spectral acceleration (S_a) as an intensity measure (IM) of an earthquake. However, there are many other earthquake IMs that were proposed by various researchers. The aim of this study is to investigate the correlation between seismic responses of NPP components and 23 earthquake IMs and identify the best IMs for correlating with damage of NPP structures. Particularly, low- and high-frequency ground motion records are separately accounted in correlation analyses. An advanced power reactor NPP in Korea, APR1400, is selected for numerical analyses where containment and auxiliary buildings are modeled using SAP2000. Floor displacements and accelerations are monitored for the non- and base-isolated NPP structures while shear deformations of the base isolator are additionally monitored for the base-isolated NPP. A series of Pearson's correlation coefficients are calculated to recognize the correlation between each of the 23 earthquake IMs and responses of NPP structures. The numerical results demonstrate that there is a significant difference in the correlation between earthquake IMs and seismic responses of non-isolated NPP structures considering low- and high-frequency ground motion groups. Meanwhile, a trivial discrepancy of the correlation is observed in the case of the base-isolated NPP subjected to the two groups of ground motions. Moreover, a selection of PGA or S_a for seismic response analyses of NPP structures in the high-frequency seismic regions may not be the best option. Additionally, a set of fragility curves are thereafter developed for the base-isolated NPP based on the shear deformation of lead rubber bearing (LRB) with respect to the strongly correlated IMs. The results reveal that the probability of damage to the structure is higher for low-frequency earthquakes compared with that of high-frequency ground motions.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.2
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• pp.49-56
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• 2010

In general, the seismic intensity deduced from instrumental data has been evaluated from the empirical relation between the intensity and the PGA. From the point of view that the degree of earthquake damage is more closely associated with the seismic intensity than with the observed PGA, JMA developed the instrumental seismic intensity (JMA instrumental intensity) meter that estimate the real-time seismic intensity from the observed strong motion data to obtain a more correct estimate of earthquake damage. The purpose of the present study is to propose a practical application of the JMA instrumental intensity in Korea. Since the occurrence of strong earthquakes is scarce in the Korean Peninsula, there is an insufficiency of strong motion data. As a result, strong motion data were synthesized by a stochastic procedure to satisfy the characteristics of a seismic source and crustal attenuation of the Peninsula. Six engineering ground motion parameters, including the JMA instrumental intensity, were determined from the synthesized strong motion data. The empirical relations between the ground motion parameters were then analyzed. Cluster analysis to classify the parameters into groups was also performed. The result showed that the JMA acceleration ($a_0$) could be classified into similar group with the spectrum intensity and the relatively distant group with the CAV (Cumulative Absolute Velocity). It is thought that the $a_0$ or JMA intensity can be used as an alternative criterion in the evaluation of seismic damage. On the other hand, attenuation relation equations for PGA and $a_0$ to be used in the prediction of seismic hazard were derived as functions of the moment magnitude and hypocentral distance.

• Smart Structures and Systems
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• v.19 no.4
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• pp.415-429
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• 2017

This paper focuses on the impact of the wave passage effect on the long-span bridge. In order to make the wave passage effect more obvious, ground motion samples are selected from the near-fault ground motion of the 1999 Chi-Chi earthquake and an arch bridge with a 280m main span is selected as a bridge sample. The motion ground samples are divided into two groups according to the characteristics of near-fault. A sequence of fragility curves is developed. It is shown that the seismic damage is increased by the wave passage effect and the increase is more obvious in the near-fault ground motion.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.265-268
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• 2008

The safety of a tunnel under seismic motion is most often evaluated by ovalling deformation of tunnel. This paper research about tunnel's longitudinal deformation. Because of spatial variation of seismic ground motion, the longitudinal structures like tunnel are likely to experience relative displacements along longitudinal direction. The spatially variable ground motion can be estimated by coherency function obtained empirically, and can be considered from different arrival times of ground motion. As a result of estimating tunnel's relative displacements at maximum curvature of tunnel, the displacements and curvatures estimated by coherency function affect the tunnel's safety more than different arrival times. However, if tunnel's displacements by coherency function superpose on displacements by different arrival times, the relative displacements and curvatures of tunnel will be more severe. Therefore, to estimate accurately tunnel's deformation in longitudinal direction has to consider both coherency and wave passage effects.