• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.652-659
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• 2005

Even in moderate to low seismic regions like Korean peninsular where wind loading usually governs the structural design of a tall building, the probable structural impact of the design basis earthquake or the maximum credible earthquake on the selected structural system should be considered at least in finalizing the design. In this study, by using response spectrum analysis and linear time history analysis method, seismic performance evaluation was conducted for wind-designed concentrically braced steel highrise buildings. Both spectrum-compatible artificial accelerograms and recorded accelerograms were used as input ground motions for the time history analysis. The analysis results showed that wind-designed concentrically braced steel highrise buildings possess significantly increased elastic seismic capacity due to the system overstrength resulting from the wind-serviceability criterion and the width-to-thickness ratio limits on steel members. Time history analysis results generally tended to underestimate the seismic response as compared to those of response spectrum analysis.

• Steel and Composite Structures
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• v.25 no.4
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• pp.473-484
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• 2017

In this study a seismic retrofit scheme for a building structure was presented using steel plate slit dampers. The energy dissipation capacity of the slit damper used in the retrofit was verified by cyclic loading test. Genetic algorithm was applied to find out the optimum locations of the slit dampers satisfying the target displacement. The seismic retrofit of the model structure using the slit dampers was compared with the retrofit with enlarging shear walls. A simple damper distribution method was proposed using the capacity spectrum method along with the damper distribution pattern proportional to the inter-story drifts. The validity of the simple story-wise damper distribution procedure was verified by comparing the results of genetic algorithm. It was observed that the capacity-spectrum method combined with the simple damper distribution pattern leaded to satisfactory story-wise distribution of dampers compatible with the optimum solution obtained from genetic algorithm.

• Earthquakes and Structures
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• v.3 no.6
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• pp.869-887
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• 2012

Ground motion scaling techniques are actively debated in the earthquake engineering community. Considerations such as what amplitude, over what period range and to what target spectrum are amongst the questions of practical importance. In this paper, the effect of various ground motion scaling approaches are explored using three reinforced concrete prototypical building models of 8, 12 and 20 stories designed to respond nonlinearly under a design level earthquake event in the seismically active Southern California region. Twenty-one recorded earthquake motions are selected using a probabilistic seismic hazard analysis and subsequently scaled using four different strategies. These motions are subsequently compared to spectrally compatible motions. The nonlinear response of a planar frameidealized building is evaluated in terms of plasticity distribution, floor level acceleration and uncorrelated acceleration amplification ratio distributions; and interstory drift distributions. The most pronounced response variability observed in association with the scaling method is the extent of higher mode participation in the nonlinear demands.

• Earthquakes and Structures
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• v.15 no.1
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• pp.29-44
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• 2018

A ground-motion prediction equation (GMPE) for the Korean Peninsula, especially for South Korea, is developed based on synthetic ground motions generated using a ground motion model derived from instrumental records from 11 recent earthquakes of $M_L$>4.5 in Korea, including the Gyeongju earthquake of Sept. 12. 2016 ($M_L$5.8). PSAs of one standard deviation from the developed GMPE with $M_W$ 6.5 at hypocentral distances of 15 km and 25 km are compared to the design spectrum (soil condition, $S_B$) of the Korean Building Code 2016 (KBC), indicating that: (1) PSAs at short periods around 0.2 sec can be 1.5 times larger than the corresponding KBC PSA, and (2) SD's at periods longer than 2 sec do not exceed 8 cm. Although this comparison of the design spectrum with those of the GMPE developed herein intends to identify the characteristics of the scenario earthquake in a lower-seismicity region such as South Korea, it does not mean that the current design spectrum should be modified accordingly. To develop a design spectrum compatible with the Korean Peninsula, more systematic research using probabilistic seismic hazard analysis is necessary in the future.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.179-186
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• 2009

This paper describes the design and implementation for spread spectrum FTS encoder and decoder. The FTS command format is defined by 64 bit encrypted packet that contains all required information relayed between the ground and the vehicle. Encryption is accomplished using the Tripple-DES encryption algorithm in block encryption form. The proposed FTS encoder and decoder is using the Convolution Encoding and Viterbi Decoding for forward error correction. The Spread Spectrum Modulation is done using a PN code, which is 256 bit gold code. The simulation result shows that the designed FTS decoder is compatible with the designed FTS encoder.

• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.5
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• pp.279-288
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• 2019

Safety-related cabinets and their electrical parts, such as relays and switches in nuclear power plants, should maintain continuous functioning, as well as structural safety according to the nuclear regulatory guidelines. Generally, an electrical part is qualified if its functioning is maintained without abnormality during excitement by motion compatible with the test response spectrum, which is larger than its in-cabinet response spectrum (ICRS). ICRS can be determined by shake-table test or dynamic analysis. Since existing cabinets in use can hardly be stopped and moved, dynamic analysis is preferred over shake-table test in determining ICRS. The simple method, suggested by the Electric Power Research Institute (EPRI) to determine ICRS, yields conservative or non-conservative results from time to time. In order to determine that the ICRS is better than EPRI method in a simple way, Ritz method considering global and local plate behaviors was suggested by Gupta et al. In this paper, the Ritz method is modified in order to consider the rocking and frame behaviors simultaneously, and it is applied to a simple numerical example for verification. ICRS is determined by Ritz method and compared with the results by finite element method (FEM). Based on this numerical example, recommendations for using Ritz method are suggested.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.1
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• pp.25-29
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• 1997

Amplication factor spectrum, using the observed strong ground motions database, has been obtained and compared with Standard Response Spectrum. The observed ground motions from the Miramichi, Nohanni, Sagueray and New Madrid Earthquake (19 vertical components, 36 horizontal components), which are estimated to represent domestic seismotectonic characteristics such as seismic sources, attenuation, and site effect, are used for the analysis of amplification factor spectrum. Amplication factors have been calculated by comparing the observed peak ground motions with results form responses to the observed horizontal and vertical ground motions. The comparison shows that the amplification factors resultant from this study exceed those of Standard Response Spectrum of relatively higher frequencies. The result implles that the characteristics of the seismic strong ground motion, which may represent the domestic seismotectonic characteristics differ from of standard Response Spectrum, especillay of higher frequencies.

• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.968-980
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• 2023

The dynamic structural responses are sensitive to the time-frequency content of seismic waves, and seismic input motions in time-history analysis are usually required to be compatible with design response spectra according to nuclear codes. In order to generate spectra-compatible input motions while maintaining the intrinsic non-stationarity of seismic waves, an improved time-domain approach is proposed in this paper. To maintain the nonstationary characteristics of the given seismic waves, a new time-frequency envelope function is constructed using the Hilbert amplitude spectrum. Based on the intrinsic mode functions (IMFs) obtained from given seismic waves through variational mode decomposition, a new corrective time history is constructed to locally modify the given seismic waves. The proposed corrective time history and time-frequency envelope function are unique for each earthquake records as they are extracted from the given seismic waves. In addition, a dimension reduction iterative technique is presented herein to simultaneously superimpose corrective time histories of all the damping ratios at a specific frequency in the time domain according to optimal weights, which are found by the genetic algorithm (GA). Examples are presented to show the capability of the proposed approach in generating spectra-compatible time histories, especially in maintaining the nonstationary characteristics of seismic records. And numerical results reveal that the modified time histories generated by the proposed method can obtain similar dynamic behaviors of AP1000 nuclear power plant with the natural seismic records. Thus, the proposed method can be efficiently used in the design practices.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.440-447
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• 2000

In order to evaluate the cost effectiveness of seismic isolation for bridges in low and moderate seismic region, a method of calculation minimum life-cycle cost of seismic-isolated bridges under specific acceleration level and soil condition is developed. Input ground motion is modeled as spectral density function compatible with response spectrum for combination of acceleration coefficient and site coefficient. Failure probability is calculated by spectrum analysis based on random vibration theories to simplify repetitive calculations in the minimization procedure. Ductility of piers and its effects on cost effectiveness are considered by stochastic linearization method. Cost function and cost effectiveness index are defined by taking into consideration the characteristics of seismic isolated bridges. Limit states for calculation of failure probability are defined on superstructure, isolator and pier, respectively. The results of example design and analysis show that seismic isolation is more cost-effective in low and moderate seismic region than in high seismic region.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.177-184
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• 2005

Even in moderate to low seismic regions like Korean peninsular where wind loading usually governs the structural design of a tall building, the probable structural impact of the design basis earthquake or the maximum credible earthquake on the selected structural system should be considered at least in finalizing the design. In this study, by using response spectrum analysis and time history analysis method, seismic performance evaluation was conducted for wind-designed concentrically braced steel highrise buildings. Input ensemble was normalized to be compatible with expected peak ground acceleration. The analysis results showed that wind-designed concentrically braced steel highrise buildings possess significantly increased elastic seismic capacity due to the system overstrength resulting from the wind-serviceability criterion and the width-to-thickness ratio limits on steel members. The time history analysis tended to significantly underestimated the seismic response as compared to response spectrum analysis. Further detailed studies regarding selection and scaling scheme of input ground motions is needed.