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11.
This paper presents a method to assess and quantify changes in performance states of systems. The method is based on survey data containing performance states graded in a suitable scale. The changes in performance states are modelled using an association matrix obtained as a frequency table of measured performance states before and after an influential incident. Performance deviation, for both negative effects induced by a harmful incident and positive effects due to a constructive incident, is modelled. Relative change in performance is quantified by defining loss and gain matrices. Hadamard products of loss/gain matrices and the association matrix obtained from survey data are used to quantify performance deviation matrices. Finally, the overall change in performance is defined in terms of a performance deviation index, which is obtained by using the sum of the elements of performance deviation matrices. This index can be negative, zero or positive, and its value represents the degree of change in performance. A negative index indicates loss in performance; a zero index implies no measurable change, and a positive index means a gain in performance. An example application of the presented methodology for earthquake-induced damage and the subsequent restoration of residential buildings in South Iceland is presented. 相似文献
12.
Sigbjørn Hervik 《Astrophysics and Space Science》2003,283(4):673-678
The early time behaviour of brane-world models is analysed in the presence of anisotropic stresses. It is shown that that
the initial singularity cannot be isotropic, unless there is also an isotropic fluid stiffer than radiation present. Also,
a magnetic Bianchi type I brane-world is analysed in detail. It is known that the Einstein equations for the magnetic Bianchi
type I models are in general oscillatory and are believed to be chaotic, but in the brane-world model this chaotic behaviour
does not seem to be possible.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
Quantification of ground-motion parameters and response spectra in the near-fault region 总被引：2，自引：1，他引：1
R. Rupakhety S. U. Sigurdsson A. S. Papageorgiou R. Sigbj?rnsson 《Bulletin of Earthquake Engineering》2011,9(4):893-930
This study focuses on the characteristics of near-fault ground motions in the forward-direction and structural response associated
with them. These ground motions are narrow-banded in nature and are characterized by a predominant period at which structures
excited by them are severely affected. In this work, predominant period is defined as the undamped natural period of a single-degree-of-freedom
(SDOF) oscillator at which its 5% damped linear elastic pseudo-spectral velocity (PSV) contains a clear and dominant peak. It is found that a linear relationship exists between predominant period and seismic
moment. An empirical equation describing this relationship is presented by using a large set of accelerograms. Attenuation
equations are developed to estimate peak ground velocity (PGV) as a function of earthquake magnitude and source-to-site distance. In addition, a predictive equation for spectral shapes
of PSV (i.e., PSV normalized by PGV) is presented as a continuous function of the undamped natural period of SDOF oscillators. The model is independent of PGV, and can be used in conjunction with any available PGV attenuation relation applicable to near-fault ground motion exhibiting forward-directivity effects. Furthermore, viscous
damping of the SDOF is included in the model as a continuous parameter, eliminating the use of so-called damping correction
factors. Finally, simple equations relating force reduction factors and displacement ductility of elasto-plastic SDOF systems
are presented. 相似文献
14.
Frequency-wavenumber (f-k) spectra of seismic strong-motion array data are useful in estimating back-azimuth and apparent propagation velocity of seismic waves arriving at the array. Such estimates are required to model wave passage effects while studying spatial variability of strong ground motion. Although periodogram-based spectral estimates are commonly used, practical applications based on them encounter limitations, such as, lack of objective criteria for selecting a proper smoothing window and its associated bandwidth, and relatively large variance of the estimated spectral quantities. We present an alternative spectral estimate based on parametric time series modelling approach. The well-known autoregressive (AR) time series model is used in a system-based approach to estimate the spectral matrix of auto- and cross-spectral densities. Such spectral estimates are found to be smoother than the windowed periodogram estimates, and can directly be used in f-k spectral analysis. We present an example application of the proposed technique using strong-motion data recorded by the SMART-1 array in Taiwan during the January 29 1981 $M_{L}$ 6.3 earthquake. Our results, in terms of back azimuth and apparent propagation velocity, are found to be in excellent agreement with those reported in the literature. 相似文献
15.
Ground-Motion Prediction Equations (GMPEs) for inelastic displacement and ductility demands of constant-strength SDOF systems 总被引：1，自引：1，他引：0
The objective of this paper is to present ground-motion prediction equations for ductility demand and inelastic spectral displacement
of constant-strength perfectly elasto-plastic single-degree-of-freedom (SDOF) oscillators. Empirical equations have been developed
to compute the ductility demand as a function of two earthquake parameters; moment magnitude, and source-to-site distance;
one site parameter, the ground type; and three oscillator parameters, an undamped natural period, critical damping ratio,
and the mass-normalized yield strength. In addition, a comparative study of the proposed model with selected previous studies
and recommendations of Eurocode 8 is presented. Proposed equations can easily be incorporated in existing probabilistic seismic
hazard analysis (PSHA) software packages with the introduction of an additional parameter. This leads to hazard curves for
inelastic spectral displacement, which can provide better estimates of target displacement for nonlinear static procedures
and an efficient intensity measure for probabilistic seismic demand analysis (PSDA). Proposed equations will be useful in
performance evaluation of existing structures. 相似文献
16.
In this article we present the modelling of uncertainty in strong-motion studies for engineering applications, particularly
for the assessment of earthquake hazard. We examine and quantify the sources of uncertainty in the basic variables involved
in ground motion estimation equations, including those associated with the seismological parameters, which we derive from
a considerable number of strong-motion records. Models derived from regression analysis result in ground motion equations
with uncertain parameters, which are directly related to the selected basic variables thus providing an uncertainty measure
for the derivative variable. These uncertainties are exemplified and quantified. An alternative approach is presented which
is based on theoretical modelling defining a functional relationship on a set of independent basic variables. Uncertainty
in the derivative variable is then readily obtained when the uncertainties of the basic variables have been defined. In order
to simplify the presentation, only the case of shallow strike-slip earthquakes is presented. We conclude that the uncertainty
is approximately the same as given by the residuals typical for regression modelling. This implies that uncertainty in ground
motion modelling cannot be reduced below certain limits, which is in accordance with findings reported in the literature.
Finally we discuss the implications of the presented methodology in hazard analyses, which is sensitive to the truncation
of the internal error term, commonly given as an integral part of ground motion estimation equations. The presented methodology
does not suffer from this shortcoming; it does not require truncation of the error term and yields realistic hazard estimates.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
Methodology for geohazard assessment for hydropower projects 总被引：1，自引：0，他引：1
Fjóla G. Sigtryggsdóttir Jónas Th. Snæbjörnsson Lars Grande Ragnar Sigbjörnsson 《Natural Hazards》2015,79(2):1299-1331
18.
K. AfifChaouch B. Tiliouine M. Hammoutene R. Sigbjörnsson R. Rupakhety 《Bulletin of Earthquake Engineering》2016,14(4):1195-1217
Spatial variability of ground motions has significant influence on dynamic response of extended structures such as bridges and tunnels. In this study, the widely used finite-source ground motion simulation approach, the so-called Empirical Green’s Function (EGF) method, is extended to synthesize seismic motions across an array of stations located at bedrock in the epicentral region of the 1980 El-Asnam region (North-West Algeria). The target event being simulated is the October 10 1980 \( M_{s} = 7.2 \) Earthquake, and the EGF is obtained from the ground motion recorded at Sogedia Factory station during the 8 November 1980 \( M_{L} = 5.6 \) aftershock. Coherency functions are then estimated from the simulated ground accelerations. A parametric study investigating the influence of shear wave velocity, earthquake magnitude, and epicentral distance is conducted by simulating ground acceleration for different scenarios using the Hybrid Green’s Function method. The main finding of the study is that finite source effects can cause significant loss in coherency at bedrock in the near-field. In the far-field, the source effect alone does not seem to produce incoherent motion, which implies that scattering and local site effects could be dominating there. Furthermore, coherency functions are found to be more sensitive to inter-station separation in the near-field than in the far-field. Increasing shear wave velocity seems to increase coherency functions, and larger earthquakes seem to produce more incoherent motion than smaller ones. The simulation method presented here produces incoherent motion mainly due to the finite source effect, while path effects are partially accounted for through the EGF, and local site effects are not considered. In this sense, the estimated coherency functions represent that of plane waves. A parametric model of plane wave coherency is calibrated and presented based on the simulation results. The results indicate that the parametric model can be used as a first approximation, and at least an upper bound of lagged coherency in the near-field region of the El-Asnam Earthquake scenario. This model could be useful in random vibration analysis or generation of spatially variable ground motion for time history analysis of lifeline structures in the study area. 相似文献
19.
Assessment of ground motion variability and its effects on seismic hazard analysis: a case study for iceland 总被引：1，自引：1，他引：0
Teraphan Ornthammarath John Douglas Ragnar Sigbj?rnsson Carlo Giovanni Lai 《Bulletin of Earthquake Engineering》2011,9(4):931-953
Probabilistic seismic hazard analysis (PSHA) generally relies on the basic assumption that ground motion prediction equations
(GMPEs) developed for other similar tectonic regions can be adopted in the considered area. This implies that observed ground
motion and its variability at considered sites could be modelled by the selected GMPEs. Until now ground-motion variability
has been taken into account in PSHA by integrating over the standard deviation reported in GMPEs, which significantly affects
estimated ground motions, especially at very low probabilities of exceedance. To provide insight on this issue, ground-motion
variability in the South Iceland Seismic Zone (SISZ), where many ground-motion records are available, is assessed. Three statistical
methods are applied to separate the aleatory variability into source (inter-event), site (inter-site) and residual (intra-event
and intra-site) components. Furthermore, the current PSHA procedure that makes the ergodic assumption of equality between
spatially and temporal variability is examined. In contrast to the ergodic assumption, several recent studies show that the
observed ground-motion variability at an individual location is lower than that implied by the standard deviation of a GMPE.
This could imply a mishandling of aleatory uncertainty in PSHA by ignoring spatial variability and by mixing aleatory and
epistemic uncertainties in the computation of sigma. Station correction coefficients are introduced in order to capture site
effects at different stations. The introduction of the non-ergodic assumption in PSHA leads to larger epistemic uncertainty,
although this is not the same as traditional epistemic uncertainty modelled using different GMPEs. The epistemic uncertainty
due to the site correction coefficients (i.e. mean residuals) could be better constrained for future events if more information
regarding the characteristics of these seismic sources and path dependence could be obtained. 相似文献
20.
Rotation-invariant measures of earthquake response spectra 总被引：1，自引：1，他引：0
A new procedure for combining the response spectra of two horizontal components of recorded ground motion is presented. The presented formulation accounts for different orientations of accelerometer sensors and derives the maximum and the expected (mean) horizontal response spectra at a site, both of which are invariant to rotation of sensor axes. The maximum response spectrum is derived as the peak resultant response of single degree of freedom oscillators subjected to the as-recorded ground acceleration. The expected spectrum is derived by projecting the displacement response (due to as-recorded motion) along two orthogonal axes to a principal axes in which the displacement responses are uncorrelated. This property is used to formulate an approximation for the expected response spectrum over all possible sensor orientations. A large set of accelerometric data from Europe and the Middle East is used to demonstrate the applicability of the proposed response spectral measures. 相似文献