Institute of Engineering Seismology and Earthquake Engineering EPPO

Thessaloníki, Greece

Institute of Engineering Seismology and Earthquake Engineering EPPO

Thessaloníki, Greece

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Savvaidis A.,Institute of Engineering Seismology and Earthquake Engineering EPPO | Margaris B.,Institute of Engineering Seismology and Earthquake Engineering EPPO | Theodoulidis N.,Institute of Engineering Seismology and Earthquake Engineering EPPO | Lekidis V.,Institute of Engineering Seismology and Earthquake Engineering EPPO | And 14 more authors.
Central European Journal of Geosciences | Year: 2014

To estimate the seismic response according to Eurocode (EC8) and almost all other national codes, site conditions have to be properly characterized so that soil amplification and the corresponding peak ground motion can be calculated. In this work, different geophysical and geotechnical methods are combined in order to define the detailed ground conditions in selected sites of the Hellenic Accelerometric Network (HAN) in Crete. For this purpose, the geological information of the sites and shear wave velocity, calculated from surface wave measurements, is used. Additionally, ground acceleration data recorded through HAN have been utilized from intermediate depth earthquakes in the broader area of South Aegean Sea. Using the recorded ground motion data and the procedure defined in EC8, the corresponding elastic response spectrum is calculated for the selected sites. The resulting information is compared to the values defined in the corresponding EC8 spectrum for the seismic zone that includes the island of Crete. The comparison shows that accurate definition of ground type through geological, geotechnical and geophysical investigations is important. However, our current comparison focuses on the distribution of values rather than the absolute values of EC8-prescribed spectra, and the results should be considered in this context. © Versita sp. z o.o.


Loupasakis C.,National Technical University of Athens | Tsangaratos P.,National Technical University of Athens | Rozos D.,National Technical University of Athens | Rondoyianni Th.,National Technical University of Athens | And 11 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

The specification of the near surface ground conditions is highly important for the design of civil constructions. These conditions determine primarily the ability of the foundation formations to bear loads, the stress - strain relations and the corresponding settlements, as well as the soil amplification and corresponding peak ground motion in case of dynamic loading. The static and dynamic geotechnical parameters as well as the ground-type/soil-category can be determined by combining geotechnical and geophysical methods, such as engineering geological surface mapping, geotechnical drilling, in situ and laboratory testing and geophysical investigations. The above mentioned methods were combined, through the Thalis "Geo-Characterization" project, for the site characterization in selected sites of the Hellenic Accelerometric Network (HAN) in the area of Crete Island. The combination of the geotechnical and geophysical methods in thirteen (13) sites provided sufficient information about their limitations, setting up the minimum tests requirements in relation to the type of the geological formations. The reduced accuracy of the surface mapping in urban sites, the uncertainties introduced by the geophysical survey in sites with complex geology and the 1D data provided by the geotechnical drills are some of the causes affecting the right order and the quantity of the necessary investigation methods. Through this study the gradual improvement on the accuracy of site characterization data is going to be presented by providing characteristic examples from a total number of thirteen sites. Selected examples present sufficiently the ability, the limitations and the right order of the investigation methods. © 2015 Copyright SPIE.


Salonikios T.N.,Institute of Engineering Seismology and Earthquake Engineering EPPO | Sextos A.G.,Aristotle University of Thessaloniki | Kappos A.J.,Aristotle University of Thessaloniki
Steel and Composite Structures | Year: 2012

The paper addresses some key issues related to the design of composite slabs with cold-formed profiled steel sheets. An experimental programme is first presented, involving six composite slab specimens tested with a view to evaluating Eurocode 4 (EC4) provisions on testing of composite slabs. In four specimens, the EC4-prescribed 5000 load cycles were applied using different load ranges resulting from alternative interpretations of the reference load Wt. Although the rationale of the application of cyclic loading is to induce loss of chemical bond between the concrete plate and the steel sheet, no such loss was noted in the tests for either interpretation of the range of load cycles. Using the recorded response of the specimens the values of factors m and k (related to interface shear transfer in the composite slab) were determined for the specific steel sheet used in the tests, on the basis of three alternative interpretations of the related EC4 provisions. The test results confirmed the need for a more unambiguous description of the m-k test and its interpretation in a future edition of the Code, as well as for an increase in the load amplitude range to be used in the cyclic loading tests, to make sure that the intended loss of bond between the concrete slab and the steel sheet is actually reached. The study also included the development of a special-purpose software that facilitates design of composite slabs; a parametric investigation of the importance of m-k values in slab design is presented in the last part of the paper.


Raptakis D.,Aristotle University of Thessaloniki | Makra K.,Institute of Engineering Seismology and Earthquake Engineering EPPO
Engineering Geology | Year: 2015

We present a detailed study of investigation of various shear wave velocity, VS, profiles at the TST site of the Euroseistest test-site. We benefit from the availability of 62 VS models derived from earthquake records, conventional seismic prospecting, and seismic noise array measurements. Five groups of models provided from many different non-invasive and invasive methods (seismic interferometry, stress-strain analysis, annealing simulation, surface wave inversion, cross-hole and down-hole tests, and seismic noise array measurements) lead to averaged VS profiles. The estimate of VS models that we obtain differs depending on the technique used. In such cases, it becomes clear that, it is better to understand the differences and not simply compute an average. The percentage of the observed disparity with respect to the average reference model albeit is small, becomes significant at certain depths and is associated with the existence of strong vertical discontinuities, thus introducing an uncertainty on the interface definition between the main formations. On the other hand, the use of VS profiles in ground simulation studies (especially 2D or 3D) usually implies the need to represent them as gradient functions. Testing representative generalized power law functions, we found that they fail to predict reliably the VS model for the total thickness of sediments. To overcome this, a third order polynomial function is proposed. Finally, we test the sensitivity of average VSz index widely used in soil categorization and site amplification studies and find that all VS models, either measured or proposed, are equivalent in terms of VSz vanishing any discrimination between layering as well as models. © 2015 Elsevier B.V.


Savvaidis A.,Institute of Engineering Seismology and Earthquake Engineering EPPO | Margaris B.,Institute of Engineering Seismology and Earthquake Engineering EPPO | Theodoulidis N.,Institute of Engineering Seismology and Earthquake Engineering EPPO | Lekidis V.,Institute of Engineering Seismology and Earthquake Engineering EPPO | And 19 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

For the seismic action estimation according to Eurocode (EC8) one has to characterize site conditions and suitably estimate soil amplification and corresponding peak ground motion for the site. For this reason, as specified, one has to define a design spectrum through the ground-type/soil-category (S), and the peak ground acceleration (PGA) of the reference return period (TNCR) for the corresponding seismic zone and for structural technical requirements chosen by the designer. Ground type is defined through geophysical/geotechnical parameters, i.e. (a) the average shear wave velocity up to 30 meters depth, (b) the Standard Penetration Test blow-count, and (c) the undrained shear strength of soil. Through the GEO-CHARACTERIZATION THALIS-PROJECT we combine different geophysical and geotechnical methods in order to more accurately define the ground conditions in selected sites of the Hellenic Accelerometric Network (HAN) in the area of Crete Island. More specifically in the present efforts, geological information shear wave velocity and attenuation model calculated from seismic surface geophysical measurements is used. Additionally we utilize the ground acceleration recorded through HAN from intermediate depth earthquakes in the broader area of South Aegean Sea. Using the recorded ground motion data and the procedure defined in EC8, the corresponding elastic response spectrum is calculated for selected sites. The resulting information are compared with the values defined for the corresponding EC8 spectrum for the seismic zone comprising the island of Crete. As a final outcome of this work we intend to propose regional normalized elastic spectra for seismic design of structures and urban development planning and compare them with Eurocode. © 2013 SPIE.


Zargli E.,Institute of Engineering Seismology and Earthquake Engineering EPPO | Liodakis S.,University of Aegean | Kyriakidis P.,University of Aegean | Kyriakidis P.,University of California at Santa Barbara | Savvaidis A.,Institute of Engineering Seismology and Earthquake Engineering EPPO
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

Continuous topography from Digital Elevation Model (DEM) data is frequently segmented into terrain classes based on local morphological characteristics of terrain elevation, e.g., local slope gradient and convexity. The resulting classes are often used as proxies for the average shear wave velocity up to 30 m, and the determination of ground types as required by the Eurocode (EC8) for computing elastic design spectra. In this work, we investigate the links between terrain related variables, particularly slope gradient, extracted for the area of Greece from the Shuttle Radar Topography Mission (SRTM) 30 arc second global topographic data available from the United States Geological Survey (USGS), with: (a) the global terrain classification product of Iwahashi and Pike (2007) in which 16 terrain types are identified for the same spatial resolution, and (b) information on geological units extracted at the same resolution from the geological map of Greece at a scale of 1/500000 as published from the Institute of Geology and Mineral Exploration (IGME). An interpretation of these links is presented within the context of understanding the reliability of using geology, slope and terrain classes for site characterizations of earthquake risk in a high seismicity area like Greece. Our results indicate that slope is a somewhat biased proxy for solid rocks, whereas in Alluvial deposits the distance to and type of the nearest geological formation appears to provide qualitative information on the size of the sedimentary deposit. © 2013 SPIE.

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