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Kostinakis K.,Aristotle University of Thessaloniki | Athanatopoulou A.,Aristotle University of Thessaloniki | Morfidis K.,Institute of Engineering Seismology and Earthquake Engineering ITSAK EPPO
Engineering Structures | Year: 2015

The present paper investigates the correlation between a large number of widely used ground motion intensity measures (IMs) and the corresponding damage to medium-rise 3D, R/C buildings. To accomplish this purpose the seismic performance of two symmetric and two asymmetric in plan 5-storey buildings subjected to 64 bidirectional earthquake ground motions are determined. Structural performance is expressed in terms of the maximum and the average interstorey drift as well as the overall structural damage index and it is determined for many angles of seismic incidence. For each individual pair of accelerograms and each seismic input angle the values of the aforementioned seismic damage measures are determined. Then, the correlation between the damage measures and the IMs is evaluated. The results reveal that the spectral acceleration at the fundamental period of the structure shows the strongest correlation with the maximum and average interstorey drifts, followed by the velocity related seismic IMs. Moreover, the vast majority of the examined ground motion IMs are proved to be inadequate to predict the overall structural damage index of frame-wall (dual) systems. © 2014 Elsevier Ltd.

Maufroy E.,French National Center for Scientific Research | Chaljub E.,French National Center for Scientific Research | Hollender F.,French National Center for Scientific Research | Hollender F.,CEA Cadarache Center | And 15 more authors.
Bulletin of the Seismological Society of America | Year: 2015

In a low-seismicity context, the use of numerical simulations becomes essential due to the lack of representative earthquakes for empirical approaches. The goals of the EUROSEISTEST Verification and Validation Project (E2VP) are to provide (1) a quantitative analysis of accuracy of the current, most advanced numerical methods applied to realistic 3D models of sedimentary basins (verification) and (2) a quantitative comparison of the recorded ground motions with their numerical predictions (validation). The target is the EUROSEISTEST site located within the Mygdonian basin, Greece. The site is instrumented with surface and borehole accelerometers, and a 3D model of the medium is available. The simulations are performed up to 4 Hz, beyond the 0.7 Hz fundamental frequency, thus covering a frequency range at which ground motion undergoes significant amplification. The discrete representation of material heterogeneities, the attenuation model, the approximation of the free surface, and nonreflecting boundaries are identified as the main sources of differences among the numerical predictions. The predictions well reproduce some, but not all, features of the actual site effect. The differences between real and predicted ground motions have multiple origins: the accuracy of source parameters (location, hypocentral depth, and focal mechanism), the uncertainties in the description of the geological medium (damping, internal sediment layering structure, and shape of the sediment-basement interface). Overall, the agreement reached among synthetics up to 4 Hz despite the complexity of the basin model, with code-to-code differences much smaller than predictions-to-observations differences, makes it possible to include the numerical simulations in site-specific analysis in the 3D linear case and low-to-intermediate frequency range. © 2015, Seismological Society of America. All rights reserved.

Hobiger M.,CNRS Institute of Earth Sciences | Cornou C.,CNRS Institute of Earth Sciences | Wathelet M.,CNRS Institute of Earth Sciences | Di Giulio G.,Institute of Engineering Seismology and Earthquake Engineering ITSAK EPPO | And 8 more authors.
Geophysical Journal International | Year: 2013

The knowledge of the local soil structure is important for the assessment of seismic hazards. A widespread, but time-consuming technique to retrieve the parameters of the local underground is the drilling of boreholes. Another way to obtain the shear wave velocity profile at a given location is the inversion of surface wave dispersion curves. To ensure a good resolution for both superficial and deeper layers, the used dispersion curves need to cover a wide frequency range. This wide frequency range can be obtained using several arrays of seismic sensors or a single array comprising a large number of sensors. Consequently, these measurements are time-consuming. A simpler alternative is provided by the use of the ellipticity of Rayleigh waves. The frequency dependence of the ellipticity is tightly linked to the shear wave velocity profile. Furthermore, it can be measured using a single seismic sensor. As soil structures obtained by scaling of a given model exhibit the same ellipticity curve, any inversion of the ellipticity curve alone will be ambiguous. Therefore, additional measurements which fix the absolute value of the shear wave velocity profile at some points have to be included in the inversion process. Small-scale spatial autocorrelationmeasurements orMASWmeasurements can provide the needed data. Using a theoretical soil structure, we show which parts of the ellipticity curve have to be included in the inversion process to get a reliable result and which parts can be omitted. Furthermore, the use of autocorrelation or high-frequency dispersion curves will be highlighted. The resulting guidelines for inversions including ellipticity data are then applied to real data measurements collected at 14 different sites during the European NERIES project. It is found that the results are in good agreement with dispersion curve measurements. Furthermore, the method can help in identifying the mode of Rayleigh waves in dispersion curve measurements. © The Authors 2012. Published by Oxford University Press on behalf of The Royal Astronomical Society.

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