The correlation between the ground motion intensity measure parameters of earthquakes (original) (raw)
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Statistical analysis of peaks and directivity of earthquake ground motion
Earthquake Engineering & Structural Dynamics, 1995
Conversion factors are useful for attenuation and damage estimation relationships. These factors among different definitions of peaks (i.e. larger, average and resultant) for peak ground motion indices and acceleration response spectrum were investigated. A large number of horizontal acceleration records recorded at 76 free-field sites of the Japan Meteorological Agency were used in this study. Two orthogonal horizontal components were combined in the time domain to get the maximum resultant peak ground motion indices and acceleration response spectrum in the horizontal plane. From the analysis, the means of the larger/resultant ratio were found to be 0.934 for acceleration, 0926 for velocity, and 0.913 for displacement. A similar decreasing trend was observed for the means of the average/resultant ratio of the ground motion indices and acceleration response spectrum. The directivity of peak ground motion indices was also examined. It was found that the peak ground motion is more likely to occur in the transverse direction than in other directions. This trend is more prominent in the long-period contents of ground motion.
Journal of Earthquake and Tsunami, 2012
Intensity measure (IM) which describes the strength of an earthquake record plays an important role in the seismic performance assessment of structures. An improved IM that can reduce the variability in seismic demands helps reducing the number of records necessary to predict the seismic performance with sufficient accuracy. In this study, an improved RMS-based IM is developed based on the results obtained from incremental dynamic analyses of short-to relatively long-period frames under an ensemble of near-fault pulse-like earthquake records. It is observed that the root-mean-square value of pseudo spectral accelerations, (Sa) rms , is generally superior to that of spectral velocities, (Sv) rms , in seismic demand prediction under near-fault records. To compute (Sa) rms as IM, two appropriate period ranges are suggested for short- and moderated-to relatively long-period frames, respectively. Comparing the efficiency of (Sa) rms with several advanced IMs shows that (Sa) rms is more e...
This paper reviews alternative selection procedures based on established methods for incorporating strong ground motion records within the framework of seismic design of structures. Given the fact that time history signals recorded at a given site constitute a random process which is practically impossible to reproduce, considerable effort has been expended in recent years on processing actual records so as to become 'representative' of future input histories to existing as well as planned construction in earthquake-prone regions. Moreover, considerable effort has been expended to ensure that dispersion in the structural response due to usage of different earthquake records is minimized. Along these lines, the aim of this paper is to present the most recent methods developed for selecting an 'appropriate' set of records that can be used for dynamic analysis of structural systems in the context of performance-based design. A comparative evaluation of the various alternatives available indicates that the current seismic code framework is rather simplified compared to what has actually been observed, thus highlighting both the uncertainties and challenges related to the selection of earthquake records.
Seismic design practices and response analyses of infrastructures have conventionally used peak ground acceleration (PGA), velocity (PGV), displacement (PGD) or spectral intensities such as spectral acceleration (Sa) and displacement (Sd) as an intensity measure (IM) of an earthquake. Previous studies showed that the conventional IMs might not be always the most desirable parameters for correlating with seismic responses and damage of structures. The correlation between earthquake IMs and seismic responses of buildings were thoroughly investigated, whereas it is not sufficiently studied yet for nuclear power plant (NPP) structures. In this study, we perform a series of time-history analyses to identify the best IMs for seismic responses of NPP components. In particular, high-frequency and low-frequency ground motions are separately investigated. An advanced power reactor NPP in Korea, APR1400, is selected for numerical analyses where containment building, auxiliary building, and internal structure are modelled using OpenSees, a platform for earthquake engineering simulations. Seismic responses of these components are obtained in terms of the maximum drift ratio and floor spectral acceleration. A series of Pearson's correlation coefficients are calculated to recognize the correlation between each of 23 earthquake IMs and responses of NPP structures. The numerical results reveal that, for the high-frequency motions, the strong correlated IMs are specific energy density (SED), characteristic intensity, root-mean-square of velocity, and Arias intensity. The poor correlated IMs are the ratio of PGV/PGA, predominant period (Tp), mean period, and cumulative absolute velocity. In case of low-frequency ground motions, the best indicators are A95 parameter, PGA, sustained maximum acceleration, effective peak acceleration. On the other hand, the weak correlated parameters are SED, PGD, Sv(T1), Sd(T1), and Tp.
Development of ground motion time histories for seismic design
2011
Structural engineers need ground motion time histories for the analysis of the response of structures to earthquake ground shaking. In current practice, these time histories are usually spectrally matched to a uniform hazard response spectrum. At low probabilities, this spectrum is too "broadband" (i.e. large over an unrealistically broad range of periods), and envelopes a set of more appropriate design response spectra, termed conditional mean spectra. These concepts are illustrated using a site-specific probabilistic seismic hazard analysis of ground shaking in which ground motion time histories are spectrally matched to conditional mean spectra that were derived from the uniform hazard spectrum.
A comprehensive near-source strong motion database was compiled. The database includes over 2,800 free-field uncorrected peak ground acceleration (PGA) values from 48 worldwide earthquakes and more than 1,300 free-field response spectra from 33 worldwide earthquakes. The database includes the data recorded within 60 km of the causative fault from earthquakes ranging from 4.7 to 7.7 in magnitude. Attenuation models of PGA and response spectra for both the vertical and horizontal components were developed as functions of magnitude, source-to-site distance, type of faulting, and local soil conditions. The study clearly demonstrates the strong dependence of vertical-to-horizontal (V/H) spectral ratio on oscillator period, source-to-site distance, and local soil conditions. V/H shows a weaker and more limited dependence on magnitude and type of faulting. The largest short-period V/H ratios are observed to occur on Holocene Soil at short periods and short distances where they can reach values in excess of 1.5 at 0.1-sec period. The largest long-period V/H ratios are observed to occur on Hard Rock where they can reach values as high as 0.7. We conclude that the standard engineering practice of assigning V/H a value of two-thirds is unconservative at short periods, especially for unconsolidated soil, but conservative at long periods, and should be modified.
On the Calculation of Peak Ground Velocity for Seismic Performance Assessment
Earthquake Spectra, 2014
Ratios of pseudo-spectral velocity (averaged over the period range of 0.5 to 2 seconds and at a period of one second) to peak ground velocity (PGV) were computed for hundreds of ground-motion records selected from the PEER NGA Strong Motion Database. Two-stage regression analyses were performed to develop models for the ratios. The inter-event terms of the ratios have the trend to decrease moderately as moment magnitude increases and the intra-event residuals do not depend on distance. The results of this study provide the technical basis for a procedure presented in the ATC-58 Guideline to estimate PGV by scaling values of pseudo-spectral velocity.
Influence of Ground Motion Duration on the Structural Response at Multiple Seismic Intensity Levels
2019
This paper aims to investigate the effects of motion duration on the structural seismic demands, seeking potential correlations between motion durations and structural responses at several seismic intensity levels. Three seismic intensity levels with 100years, 475years, and 2475years earthquake return periods (RPs) are first considered for correlation computations. Spectrally matched ground motions are employed to isolate the contribution of duration from the effects of ground motion amplitudes and response spectral shape. Four single degree of freedom systems derived from four real reinforced concrete structures are studied, where both degrading and non-degrading equivalent SDOF systems are included for structural modeling. Results show a low positive correlation between motion duration and structural displacement demand, but this correlation increases with an increase in earthquake RP. It is also investigated whether or not this insignificant positive correlation has an impact on ...
Scaling and Selection of Ground Motion Records for Nonlinear Response History Analysis of Structures
2012
Accurate estimation of structural response for a given target hazard level requires a suitable set of ground-motion records that represents a pre-defined scenario event. With the aim of assessing the seismic performance of structural systems, this study presents a ground motion selection and scaling methodology. Given a relatively larger ground-motion database, the method uses the differences between individual records and corresponding estimations of a ground-motion prediction equation in order to determine the optimum subset of recordings. This way, the procedure provides a group of modified records whose median elastic spectral ordinate matches with the target intensity level without excessively manipulating the inherent aleatory variability in the selected recordings. Considering the sensitivity of overall structural response to the nonlinear behavior, the procedure approximately estimates the median and dispersion of inelastic structural response. The case study suggests that, ...