• Proceedings of the KSR Conference
• /
• 2010.06a
• /
• pp.872-879
• /
• 2010

High rock-fill embankment is relatively flexible, which makes crest of embankment subject to excessive amplification in displacement due to earthquake loading. To overcome problems related with site response in high embankment, it is essential to evaluate shear-wave velocity profile of the embankment with improved accuracy and reliability. In this aspect, an experimental research was performed to answer how to perform surface-wave tests and to analyze measurements at an embankment site with a sloping ground surface. Unlike flat ground surface, sloping ground may hamper and slow down propagation of surface waves due to multiple reflections and refractions in embankment. To figure out this reasoning for the effect of multiple reflections and refractions due to sloping surface, surface wave tests were performed at a reservoir embankment of Chung-Song in North KyeongSang Province. Parameters involved in surface wave tests at non-flat surface, including source directionality, geometry-related constraint and frequency components in source function, were investigated using field measurements.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.7 no.4
• /
• pp.23-30
• /
• 2003

The result of recent seismic hazard analysis indicates that the ground motion response spectra for Korean nuclear power plant site have relatively large frequency acceleration contents. In the ordinary seismic fragility analysis of nuclear power plant structures and equipments, the safety margin of design ground response spectrum is directly used as a response spectrum shape factor. The effects of input response spectrum shape on the floor response spectrum were investigated by performing the direct generation of floor response spectrum from the ground response spectrum. The safety margin included in the design ground response spectrum should be considered as a floor response spectrum shape factor for the seismic fragility analysis of the equipments located in a building.

• Earthquakes and Structures
• /
• v.13 no.2
• /
• pp.193-200
• /
• 2017

To overcome the difficulty of performing multi-point response spectrum analysis for engineering structures under spatially varying ground motions (SVGM) using the general finite element code such as ANSYS, an approach has been developed by improving the modelling of the input ground motions in the spectral analysis. Based on the stochastic vibration analyses, the cross-power spectral density (c-PSD) matrix is adopted to model the stationary SVGM. The design response spectra are converted into the corresponding PSD model with appropriate coherency functions and apparent wave velocities. Then elements of c-PSD matrix are summarized in the row and the PSD matrix is transformed into the response spectra for a general spectral analysis. A long-span high-pier bridge under multiple support excitations is analyzed using the proposed approach considering the incoherence, wave-passage and site-response effects. The proposed approach is deemed to be an efficient numerical method that can be used for seismic analysis of large engineering structures under SVGM.

• Geomechanics and Engineering
• /
• v.18 no.6
• /
• pp.639-650
• /
• 2019

Time-domain commercial codes are widely used to evaluate the seismic behavior of tunnels. Those tools offer a good insight into the performance and the failure mechanism of tunnels under earthquake loading. Viscous damping is generally employed in the dynamic analysis to consider damping at very small strains in some cases, and the Rayleigh damping is commonly used one. Many procedures to obtain the damping parameters have been proposed but they are seldom discussed. This paper illustrates the influence of the Rayleigh damping formulation on the tunnel visco-elastic behavior under earthquake. Four Rayleigh damping determination procedures and three soil shear velocity profiles are accounted for. The results show significant differences in the free-field and in the tunnel response caused by different procedures. The difference is somewhat decreased when the soil site fundamental frequency is increased. The conventional method which consists of using solely the first soil natural mode to determine the viscous damping parameters may lead to an unsafe seismic design of the tunnel. In general, using five times site fundamental frequency to obtain the damping formulation can provide relatively conservative results.

• Journal of Korean Society of societal Security
• /
• v.2 no.2
• /
• pp.69-74
• /
• 2009

The purpose of this research is to assess the aseismic safety for the large-sized waste landfill site based on the results from liquefaction potential analysis. For successful achievement of research, the simplified liquefaction analysis and detailed liquefaction analysis using data from lab test and seismic response analysis are executed. Based on the simplified liquefaction analysis, the possibility of liquefaction is occurred at only BH-14 with maximum acceleration 0.169 g. Therefore, liquefaction possibility of BH-14 is evaluated by the detailed liquefaction analysis again. The safety factor greater than 1.0 from the result of analysis at BH-14 guarantees safety of liquefaction.

• Wind and Structures
• /
• v.16 no.4
• /
• pp.373-391
• /
• 2013

This is the first of two companion papers that analyse ten years of on-site monitoring data for the Confederation Bridge to determine the validity of the original wind speeds and wind loads predicted in 1994 when the bridge was being designed. The check of the original design values is warranted because the design wind speed at the middle of Northumberland Strait was derived from data collected at shore-based weather stations, and the design wind loads were based on tests of section and full-aeroelastic models in the wind tunnel. This first paper uses wind, tilt, and acceleration monitoring data to determine the static and dynamic responses of the bridge, which are then used in the second paper to derive the static and dynamic wind loads. It is shown that the design ten-minute mean wind speed with a 100-year return period is 1.5% less than the 1994 design value, and that the bridge has been subjected to this design event once on November 7, 2001. The dynamic characteristics of the instrumented spans of the bridge including frequencies, mode shapes and damping are in good agreement with published values reported by others. The on-site monitoring data show bridge response to be that of turbulent buffeting which is consistent with the response predicted at the design stage.

• Journal of the Korean Geotechnical Society
• /
• v.37 no.12
• /
• pp.7-23
• /
• 2021

Underground utility tunnels, which contribute to supply of electricity, communication, water and heat, are critical lifelines of an urban area. In case service is discontinued or functional disruption happens, there will be a huge socio-economic impact. For the improved seismic design and evaluation of underground structures, this study proposes a ground displacement measure when the site is subjected to a scenario earthquake based on hazard-consistent source spectra and site amplification/attenuation. This measure provides a rational estimation of ground displacement and can be an alternative to existing response displacement methods.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2007.09a
• /
• pp.266-292
• /
• 2007

Round Robin Test (RRT) on ground response analyses was conducted for three sites in Korea based on several site investigation data, which include borehole logs with the N values from standard penetration test (SPT) for all three sites and additionally cone tip resistance profiles for two sites. Three input earthquake motions together with the site investigation data were provided for the RRT. A total of 12 teams participating in this RRT presented the results of ground response analyses using equivalent-linear and/or nonlinear method. Each team determined input geotechnical properties by using empirical relationships and literatures based on own judgment, with the exception of the input motions. Herein, the characteristics of input motions were compared in terms of the frequency and period, and the selection of the depth to bedrock, on which the motions is impinged, was discussed considering geologic conditions in Korea. Furthermore, a variety of geotechnical properties such as shear wave velocity profiles and soil nonlinear curves were investigated with the input properties used in this RRT.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 1998.04a
• /
• pp.212-219
• /
• 1998

Dynamic analyses are performed for the wood structure modeled as a SDOF hysteretic system. The hysteresis model presented is a modified version of Takeda model. The comparison between the results of numerical simulation and the experimental results show good agreements in overall tendencies. The response of wood structure subjected to artificially generated earthquakes considering site effects is studied. It appears that the response is very strongly influenced by the intensity and the frequency contents of the ground motion.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.25 no.5
• /
• pp.223-232
• /
• 2021

The spatial variation characteristics of seismic motions at the nuclear power plant's site and structures were analyzed using earthquake records obtained at the Fukushima nuclear power plant during the Great East Japan Earthquake. The ground responses amplified as they approached the soil surface from the lower rock surface, and the amplification occurred intensively at about 50 m near the ground. Due to the soil layer's nonlinear characteristics caused by the strong seismic motion, the ground's natural frequency derived from the response spectrum ratio appeared to be smaller than that calculated from the shear wave velocity profile. The spatial variation of the peak ground acceleration at the ground surface of the power plant site showed a significant difference of about 0.6 g at the maximum. As a result of comparing the response spectrums at the basement of the structure with the design response spectrum, there was a large variability by each power plant unit. The difference was more significant in the Fukushima Daiichi site record, which showed larger peak ground acceleration at the surface. The earthquake motions input to the basement of the structure amplified according to the structure's height. The natural frequency obtained from the recorded results was lower than that indicated in the previous research. Also, the floor response spectrum change according to the location at the same height was investigated. The vertical response on the foundation surface showed a significant difference in spectral acceleration depending on the location. The amplified response in the structure showed a different variability depending on the type of structure and the target frequency.