• Structural Engineering and Mechanics
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• 제59권4호
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• pp.653-669
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• 2016

Recent earthquakes worldwide show that a significant portion of the earthquake shaking happens in the vertical direction. This phenomenon has raised significant interests to consider the vertical ground motion during the seismic design and assessment of the structures. Strong vertical ground motions can alter the axial forces in the columns, which might affect the shear capacity of reinforced concrete (RC) members. This is particularly important for non-ductile RC frames, which are very vulnerable to earthquake-induced collapse. This paper presents the detailed nonlinear dynamic analysis to quantify the collapse risk of non-ductile RC frame structures with varying heights. An array of non-ductile RC frame architype buildings located in Los Angeles, California were designed according to the 1967 uniform building code. The seismic responses of the architype buildings subjected to concurrent horizontal and vertical ground motions were analyzed. A comprehensive array of ground motions was selected from the PEER NGA-WEST2 and Iran Strong Motions Network database. Detailed nonlinear dynamic analyses were performed to quantify the collapse fragility curves and collapse margin ratios (CMRs) of the architype buildings. The results show that the vertical ground motions have significant impact on both the local and global responses of non-ductile RC moment frames. Hence, it is crucial to include the combined vertical and horizontal shaking during the seismic design and assessment of non-ductile RC moment frames.

• 한국지진공학회논문집
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• 제20권5호
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• pp.331-340
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• 2016

It is important to select proper ground motions for obtaining accurate results from response history analyses. The purpose of this study is to propose an accurate and efficient method that does not require excessive computation for selecting and scaling ground motions to match target response spectrum mean and variance. The proposed method is conceptually simple and straightforward, and it does not use a simulation algorithm that requires a sophisticated subroutine program. In this method, the desired number of ground motions are sequentially scaled and selected from a ground motion library. The proposed method gives the best selection results using Sum of Square Error and has the smallest value(=0.14). Also, The accuracy and consistency of the proposed method are verified by comparing the selection results of the proposed method with those of existing methods.

• Earthquakes and Structures
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• 제20권1호
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• pp.87-96
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• 2021

Ground motions recorded in near-fault sites, where the rupture propagates toward the site, are significantly different from those observed in far-fault regions. In this research, finite element modeling is used to investigate the effect of pile cap stiffness on the seismic response of soil-pile-structure systems under near-fault ground motions. The Von Wolffersdorff hypoplastic model with the intergranular strain concept is applied for modeling of granular soil (sand) and the behavior of structure is considered to be non-linear. Eight fault-normal near-field ground motion records, recorded on rock, are applied to the model. The numerical method developed is verified by comparing the results with an experimental test (shaking table test) for a soil-pile-structure system. The results, obtained from finite element modeling under near-fault ground motions, show that when the value of cap stiffness increases, the drift ratio of the structure decreases, whereas the pile relative displacement increases. Also, the residual deformations in the piles are due to the non-linear behavior of soil around the piles.

• Structural Engineering and Mechanics
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• 제82권3호
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• pp.325-341
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• 2022

Previous major earthquakes indicated that the earthquake induced ground motions are typical non-stationary processes, which are non-stationary in both amplification and frequency. For the convenience of aseismic design and analysis, it usually assumes that the ground motions at structural supports are stationary processes. The development of time-frequency analysis technique makes it possible to evaluate the non-stationary responses of engineering structures subjected to non-stationary inputs, which is more general and realistic than the analysis method commonly used in engineering. In this paper, the wavelet-based stochastic vibration analysis methodology is adopted to calculate the non-stationary responses of multi-support structures. For comparison, the stationary response based on the standard random vibration method is also investigated. A frame structure and a two-span bridge are analyzed. The effects of non-stationary spatial ground motion and local site conditions are considered, and the influence of structural property on the structural responses are also considered. The analytical results demonstrate that the non-stationary spatial ground motions have significant influence on the response of multi-support structures.

• 한국안전학회지
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• 제20권3호
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• pp.143-151
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• 2005

In this study, it is demonstrated that how the effect of the Near Fault Ground Motion affects the response of the structure. Considering the general characteristic of Near Fault Ground Motion the characteristics of Near Fault Ground Motions is analysed by elastic response spectrums, and the inelastic response spectrum is evaluated with the ductility and the yield strength to consider the inelastic behavior which couldn't be simulated through the elastic response spectrum. The result of this study shows that the effect of Near Fault Ground Motion should be considered in the long period range of long span structures but the domestic seismic design code was developed based on Far Fault Ground Motions, so the effects of Near Fault Ground Motions, which is very serious especially in large structures with a long period, are not considered. Therefore, the effect of the Near Fault Ground Motion has to be examined especially in the seismic performance evaluation of long period structure.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 봄 학술발표회 논문집
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• pp.243-249
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• 2003

The characteristics of harmonic phase angles and phase angle differences contained in earthquake ground motions such as El Centre 1530 NS, Taftl 1952 NS, Hachinohe 1968 NS and Mexico 1985 are figured, which have been mostly overlooked in contrast with the importance placed on harmonic amplitudes. And, energy input spectrum of structures excited by such an earthquake motion is expressed with smoothed Fourier amplitude spectrum. In dynamic response analysis, there must be earthquake ground accelerations which contain the phase angle, the phase angle difference and energy input spectrum characteristics of the zone considered to be constructed building structures. To make clear the importance of phase angle differences, 4-earthquake ground motions are normalized by 200 gal and energy input spectrum characteristics of normalized 4-earthquake ground motions are compared.

• 대한자원환경지질학회:학술대회논문집
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• 대한자원환경지질학회 1999년도 춘계 공동학술발표회
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• pp.116-119
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• 1999

Amplification factor spectrum, using the observed strong ground motions database in the Korean Peninsula, has been obtained and compared with Standard Response Spectrum, which was suggested by United States Nuclear Regulatory Committee. The observed und motions from the Yongwol and the Kyoungju, and the other recent Earthquakes, respectively, which ate supposed to represent domestic seismotectonic characteristics such as seismic source, attenuation of the propagation medium, and site specific effect, are used for the analysis of amplification factor spectrum. The database are slightly different from the those of the second study. Amplification factors hue been calculated by comparing the observed peak ground motions with results from responses to the observed horizontal na vertical ground motions. The comparison have shown that the amplification factors resultant from this study exceeds these of Standard Response Spectrum, The results suggest that the characteristics of seismic strong ground motion, which are supposed to represent the domestic seismotectonic characteristics, differs from those of Standard Response Spectrum, especially at higher frequencies. The results from the 2nd study are similar to those of 1st analysis.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.497-504
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• 2002

The characteristics of harmonic phase angles and phase angle differences contained in earthquake ground motions such as El Centre 1940 NS, Taft1 1952 NS, Hachinohe 1968 NS and Mexico 1985 are figured, which have been mostly overlooked in contrast with the importance placed on harmonic amplitudes. Recently, performance based design method is used for seismic design and seismic retrofitting, which needs nonlinear response analysis, there must be earthquake ground accelerations which contain the phase angle and the phase angle difference characteristics of the zone considered to be constructed building structures. To make clear the importance of phase angle differences, 4-earthquake ground motions are normalized by 200 gal and nonlinear response characteristics of normalized 4-earthquake ground motions are compared.

• Structural Engineering and Mechanics
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• 제62권4호
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• pp.497-506
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• 2017

A low damage self-centering braced frame equipped with post-tensioning strands is capable of directing damage to replaceable butterfly-shaped fuses. This paper investigates the seismic performance of rocking braced frame under near-field pulse-like ground motions compared to far-field records. A non-linear time history analysis is performed for twelve self-centering archetypes. A sensitivity analysis is carried out to examine the influences of ground motion types and modeling parameters. Findings represent the proper efficiency of the self-centering system under both far-field and near-field pulse-like ground motions.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1999년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.61-68
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• 1999

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 known 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 modulation function and a power spectral density function to describe such non-stationary characteristics. Satio and Wen(1994) proposed a non-stationary stochastic process model to generate earthquake ground motions which are compatible with design reponse spectrum at sites in Japan. this paper shows the process to modify power spectrum compatible with target design response spectrum for generating of nonstationary artificial earthquake ground motions. Target reponse spectrum is chosen by ATC14 to calibrate the response spectrum according to a give recurrence period.