• Title, Summary, Keyword: ground motion

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Scaled and unscaled ground motion sets for uni-directional and bi-directional dynamic analysis

  • Kayhan, Ali Haydar
    • Earthquakes and Structures
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    • v.10 no.3
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    • pp.563-588
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    • 2016
  • In this study, solution models are proposed to obtain code-compatible ground motion record sets which can be used for both uni-directional and bi-directional dynamic analyses. Besides scaled, unscaled ground motion record sets are obtained to show the utility and efficiency of the solution models. For scaled ground motion sets the proposed model is based on hybrid HS-Solver which integrates heuristic harmony search (HS) algorithm with the spreadsheet Solver add-in. For unscaled ground motion sets HS based solution model is proposed. Design spectra defined in Eurocode-8 for different soil types are selected as target spectra. The European Strong Motion Database is used to get ground motion record sets. Also, a sensitivity analysis is conducted to evaluate the effect of different HS solution parameters on the solution accuracy. Results show that the proposed solution models can be regarded as efficient ways to develop scaled and unscaled ground motion sets compatible with code-based design spectra.

Seismic fragility curves using pulse-like and spectrally equivalent ground-motion records

  • Surana, Mitesh
    • Earthquakes and Structures
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    • v.19 no.2
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    • pp.79-90
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    • 2020
  • 4- and 8-storey reinforced-concrete frame buildings are analyzed under the suites of the near-fault pulse-like, and the corresponding spectrally equivalent far-fault ground-motion records. Seismic fragility curves for the slight, moderate, extensive, and complete damage states are developed, and the damage probability matrices, and the mean loss ratios corresponding to the Design Basis Earthquake and the Maximum Considered Earthquake hazard levels are compared, for the investigated buildings and sets of ground-motion records. It is observed that the spectrally equivalent far-fault ground-motion records result in comparable estimates of the fragility curve parameters, as that of the near-fault pulse-like ground-motion records. As a result, the derived damage probability matrices and mean loss ratios using two suites of ground-motion records differ only marginally (of the order of ~10%) for the investigated levels of seismic hazard, thus, implying the potential for application of the spectrally equivalent ground-motion records, for seismic fragility and risk assessment at the near-fault sites.

Estimation of Path Attenuation Effect from Ground Motion in the Korean Peninsula using Stochastic Point-source Model (추계학적 점지진원 모델을 사용한 한반도 지반 운동의 경로 감쇠 효과 평가)

  • Jee, Hyun Woo;Han, Sang Whan
    • Journal of the Earthquake Engineering Society of Korea
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    • v.24 no.1
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    • pp.9-17
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    • 2020
  • The stochastic point-source model has been widely used in generating artificial ground motions, which can be used to develop a ground motion prediction equation and to evaluate the seismic risk of structures. This model mainly consists of three different functions representing source, path, and site effects. The path effect is used to emulate decay in ground motion in accordance with distance from the source. In the stochastic point-source model, the path attenuation effect is taken into account by using the geometrical attenuation effect and the inelastic attenuation effect. The aim of this study is to develop accurate equations of ground motion attenuation in the Korean peninsula. In this study, attenuation was estimated and validated by using a stochastic point source model and observed ground motion recordings for the Korean peninsula.

Statistical evaluation of drift demands of rc frames using code-compatible real ground motion record sets

  • Kayhan, Ali Haydar;Demira, Ahmet
    • Structural Engineering and Mechanics
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    • v.60 no.6
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    • pp.953-977
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    • 2016
  • Modern performance-based design methods require ways to determine the factual behavior of structures subjected to earthquakes. Drift ratio demands are important measures of structural and/or nonstructural damage of the structures in performance-based design. In this study, global drift ratio and interstory drift ratio demands, obtained by nonlinear time history analysis of three generic RC frames using code-compatible ground motion record sets, are statistically evaluated. Several ground motion record sets compatible with elastic design spectra defined for the local soil classes in Turkish Earthquake Code are used for the analyses. Variation of the drift ratio demands obtained from ground motion records in the sets and difference between the mean of drift ratio demands calculated for ground motion sets are evaluated. The results of the study indicate that i) variation of maximum drift ratio demands in the sets were high; ii) different drift ratio demands are calculated using different ground motion record sets although they are compatible with the same design spectra; iii) the effect of variability due to random causes on the total variability of drift ratio demands is much larger than the effect of variability due to differences between the mean of ground motion record sets; iv) global and interstory drift ratio demands obtained for different ground motion record sets can be accepted as simply random samples of the same population at %95 confidence level. The results are valid for all the generic frames and local soil classes considered in this study.

Simulation method of ground motion matching for multiple targets and effects of fitting parameter variation on the distribution of PGD

  • Wang, Shaoqing;Yu, Ruifang;Li, Xiaojun;Lv, Hongshan
    • Earthquakes and Structures
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    • v.16 no.5
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    • pp.563-573
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    • 2019
  • When generating spectrum-compatible artificial ground motion in engineering practices, the effect of the variation in fitting parameters on the distribution of the peak ground displacement (PGD) has not yet drawn enough attention. In this study, a method for simulating ground motion matching for multiple targets is developed. In this method, a frequency-dependent amplitude envelope function with statistical parameters is introduced to simulate the nonstationarity of the frequency in earthquake ground motion. Then, several groups of time-history acceleration with different temporal and spectral nonstationarities were generated to analyze the effect of nonstationary parameter variations on the distribution of PGD. The following conclusions are drawn from the results: (1) In the simulation of spectrum-compatible artificial ground motion, if the acceleration time-history is generated with random initial phases, the corresponding PGD distribution is quite discrete and an uncertain number of PGD values lower than the limit value are observed. Nevertheless, the mean values of PGD always meet the requirement in every group. (2) If the nonstationary frequencies of the ground motion are taken into account when fitting the target spectrum, the corresponding PGD values will increase. A correlation analysis shows that the change in the mean and the dispersion values, from before the frequencies are controlled to after, correlates with the modal parameters of the predominant frequencies. (3) Extending the maximum period of the target spectrum will increase the corresponding PGD value and, simultaneously, decrease the PGD dispersion. Finally, in order to control the PGD effectively, the ground motion simulation method suggested in this study was revised to target a specified PGD. This novel method can generate ground motion that satisfies not only the required precision of the target spectrum, peak ground acceleration (PGA), and nonstationarity characteristics of the ground motion but also meets the required limit of the PGD, improving engineering practices.

Site specific ground motion simulation and seismic response analysis for microzonation of Kolkata

  • Roy, Narayan;Sahu, R.B.
    • Geomechanics and Engineering
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    • v.4 no.1
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    • pp.1-18
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    • 2012
  • The spatial variation of ground motion in Kolkata Metropolitan District (KMD) has been estimated by generating synthetic ground motion considering the point source model coupled with site response analysis. The most vulnerable source was identified from regional seismotectonic map for an area of about 350 km radius around Kolkata. The rock level acceleration time histories at 121 borehole locations in Kolkata for the vulnerable source, Eocene Hinge Zone, due to maximum credible earthquake (MCE) moment magnitude 6.2 were generated by synthetic ground motion model. Soil investigation data of 121 boreholes were collected from the report of Soil Data Bank Project, Jadavpur University, Kolkata. Surface level ground motion parameters were determined using SHAKE2000 software. The results are presented in the form of peak ground acceleration (PGA) at rock level and ground surface, amplification factor, and the response spectra at the ground surface for frequency 1.5 Hz, 3 Hz, 5 Hz and 10 Hz and 5% damping ratio. Site response study shows higher PGA in comparison with rock level acceleration. Maximum amplification in some portion in KMD area is found to be as high as 3.0 times compared to rock level.

Effects of Vertical Ground Motion on Rocking Response of Free Standing Structure (연직지반운동이 자립형 구조체의 Rocking 거동에 미치는 영향)

  • 최인길;전영선
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.169-176
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    • 1997
  • In this study, vertical ground motion effects on rocking response of free standing structure are investigated. Based on the mathematical model, computer program is developed using Kutta's Fourth-Order Method. Using the program, several parametric studis are performed to predict the effects of vertical ground motion. From the results of this study, it can be found that the vertical ground motion may overturn the structure which is stable under the horizontal ground motion, stabilize the structure which overturns due to horizontal ground motion alone, and delay the time of overturning of the structure or greatly reduce the rocking of the structure. It is concluded that the effect of vertical ground motion on the rocking response of free standing structure is apparently not systematic.

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Characterization and modeling of near-fault pulse-like strong ground motion via damage-based critical excitation method

  • Moustafa, Abbas;Takewaki, Izuru
    • Structural Engineering and Mechanics
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    • v.34 no.6
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    • pp.755-778
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    • 2010
  • Near-fault ground motion with directivity or fling effects is significantly influenced by the rupture mechanism and substantially different from ordinary records. This class of ground motion has large amplitude and long period, exhibits unusual response spectra shapes, possesses high PGV/PGA and PGD/PGA ratios and is best characterized in the velocity and the displacement time-histories. Such ground motion is also characterized by its energy being contained in a single or very few pulses, thus capable of causing severe damage to the structures. This paper investigates the characteristics of near-fault pulse-like ground motions and their implications on the structural responses using new proposed measures, such as, the effective frequency range, the energy rate (in time and frequency domains) and the damage indices. The paper develops also simple mathematical expressions for modeling this class of ground motion and the associated structural responses, thus eliminating numerical integration of the equations of motion. An optimization technique is also developed by using energy concepts and damage indices for modeling this class of ground motion for inelastic structures at sites having limited earthquake data.

A Study on Characteristics and Dynamic Response Spectrum of Near Fault Ground Motions (근거리지진의 특성과 동적응답스펙트럼에 관한 연구)

  • Bang, Myung-Seok;Han, Sung-Ho
    • Journal of the Korean Society of Safety
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    • v.20 no.3
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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.

Empirical ground motion model for Vrancea intermediate-depth seismic source

  • Vacareanu, Radu;Demetriu, Sorin;Lungu, Dan;Pavel, Florin;Arion, Cristian;Iancovici, Mihail;Aldea, Alexandru;Neagu, Cristian
    • Earthquakes and Structures
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    • v.6 no.2
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    • pp.141-161
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    • 2014
  • This article presents a new generation of empirical ground motion models for the prediction of response spectral accelerations in soil conditions, specifically developed for the Vrancea intermediate-depth seismic source. The strong ground motion database from which the ground motion prediction model is derived consists of over 800 horizontal components of acceleration recorded from nine Vrancea intermediate-depth seismic events as well as from other seventeen intermediate-depth earthquakes produced in other seismically active regions in the world. Among the main features of the new ground motion model are the prediction of spectral ordinates values (besides the prediction of the peak ground acceleration), the extension of the magnitudes range applicability, the use of consistent metrics (epicentral distance) for this type of seismic source, the extension of the distance range applicability to 300 km, the partition of total standard deviation in intra- and inter-event standard deviations and the use of a national strong ground motion database more than two times larger than in the previous studies. The results suggest that this model is an improvement of the previous generation of ground motion prediction models and can be properly employed in the analysis of the seismic hazard of Romania.