Johann Facciorusso

Influence of uncorrected accelerogram processing techniques on Newmark's rigid block displacement evaluation

Design seismic motion represents a fundamental issue of many geotechnical applications. In more complex numerical procedures, input motion is required in the complete form of an accelerogram, whereas in simplified prediction methods it is generally expressed by means of synthetic parameters such as peak ground acceleration, peak ground velocity, Arias intensity, etc. The aim of this paper is to show the sensitiveness of these parameters to small changes in the characteristics of the accelerogram associated with the filtering procedures used for reducing digitisation errors, instrument distortions, etc. and the influence of the consequent uncertainties on geotechnical applications. More specifically this paper examines the incidence of processing techniques of uncorrected records from Italian accelerograph network on slope displacement evaluation based on Newmarks rigid block model.

CPT-Based Liquefaction Case History from the 2012 Emilia Earthquake in Italy

AbstractSignificant and widespread liquefaction phenomena were observed after the main shock of the Emilia earthquake (Italy) on May 20, 2012. A considerable number of surveys were subsequently performed to accurately test the susceptibility to liquefaction of soil deposits affected by the most severe liquefaction-induced effects and damage. Ground surface morphology was defined in detail by means of LIDAR survey results; subsoil stratigraphy and water table level were inferred from CPT tests and soundings; physical properties and mechanical parameters of soils were obtained from laboratory tests or indirectly inferred from the results of a large number of CPT tests carried out in the area. Two main sandy layers susceptible to liquefaction were identified and appropriately characterized. Seismic loading induced by the main shocks of the sequence was carefully estimated from the peak ground acceleration map produced by the National Institute of Geophysics and Volcanology. More than 90 sites were examined i...

Soil Liquefaction During the Emilia, 2012 Seismic Sequence: Investigation and Analysis

In the framework of a Project issued by the Italian National Institute of Geophysics and Volcanology (INGV) a Research Unit (RU) has been granted with the commitment to provide a link between the seismic shaking and the triggering of ground failures such as liquefaction. The main goals have regarded both the enlargement of the base of observables for a better constrain of the seismic hazard assessments and the analysis of the triggering and causative factors of permanent ground deformations. Nevertheless, when analyzing the non-linear soil response under which liquefaction occur, some insights into site-effects have been also provided, thus contributing to the general task of the site-specific hazard. The paper illustrates the analyses and investigations carried out within the aim of the project, some of them are still provisional due to the huge amount of data produced and the strong effort required to analyze all the matters related to the observed phenomena.

A Methodology for Advanced Seismic Microzoning Using 2D Analyses: The Case Study of Barberino di Mugello, Florence, Italy

The here presented study was developed in the frame of the VEL/DOCUP projects promoted by the Regional Government of Tuscany (Central Italy) in order to mitigate the risk from earthquake. It concerns the assessment of local seismic effects aimed at drawing up a detailed seismic microzoning map for an area including some villages, industrial and commercial settlements close to the most important town of western Mugello, one of the highest seismicity zones of the Northern Apennine Chain. Geological subsoil modelling and geotechnical characterization of the area under study were performed by using the results of an in-depth survey including in situ and laboratory tests. On the basis of geomorphologic and lithostratigraphic data, a first level of seismic zoning map was prepared aimed to recognize areas involved in different kinds of geotechnical phenomena (amplification, slope-instability, liquefaction, etc.) and several representative cross sections were then identified for the whole area under study. Numerical 2D analyses were implemented on the selected cross sections to quantify the local seismic response on ground surface. The performed analyses allowed to recognize zones with different seismic response in term of a suitable selected amplification factor and to draw a Level 3 seismic microzonation map according to the procedure recommended by the Italian guidelines for microzoning. In this paper the results of two-dimensional local seismic response analyses and advanced seismic microzonation mapping for the area under study are presented and discussed.

Soil Liquefaction Analyses in a Test-Area Affected by the 2012 Emilia-Romagna Earthquake (Italy)

Significant and widespread liquefaction effects were observed in the area of San Carlo and Mirabello villages during the Emilia-Romagna earthquake of May 20 and 29, 2012. After the earthquake, an intensive program of laboratory and in situ (mostly CPT’s) tests was carried out in the affected area. The stratigraphic and geotechnical conditions have been found to predispose the soil deposits to liquefaction phenomena. The triggering conditions, i.e. the design earthquake parameters, have been evaluated according to the most recent seismic hazard analyses and local seismic response analyses. The liquefaction risk, expressed in term of liquefaction potential index (LPI), was determined by using the CPT-based simplified method of Robertson and Wride. The obtained results are not consistent with the observed liquefaction effects and the liquefaction risk seems to be systematically underestimated. In the present paper the reason of this underestimation is investigated and a possible correction for applying the simplified cyclic stress approaches is proposed.

Local Seismic Response Prediction and Design Building Code Provisions : The Case Study of Senigallia, Italy

With the aim to contribute to the discussion on the validation of European and Italian design building code spectra, this paper describes and discusses the results obtained by means of equivalent linear analyses performed in a number of well documented test sites located alongside the Adriatic coast, in the town of Senigallia, Central Italy. Given the medium intensity shaking expected in the area (peak ground acceleration of 0.20g at ‘rock-like’ formation with a return period of 475 years) and the likely strain levels that can be induced on soils, and also given the geomorphologic characteristics of the site (mainly consisting of a Plio-Pleistocene clayey-marly bedrock underlying Quaternary plain deposits and alluvial terraces where 2-D effects appear to be not influent) a 1-D linear equivalent model was employed for seismic site response evaluation. The seismic response analyses were performed on eight different soil profiles where dynamic soil properties were accurately measured. In order to reduce the input seismic ground motions uncertainties Both real selected acceleration time histories and simulated accelerograms obtained by a seismic wave propagation model were assumed in the analyses,. The obtained results are synthesised in this paper and the elastic response spectra obtained at ground surface are compared with those provided by Eurocode 8 for the corresponding ground types. The practical significance, implications and applications of the spectra obtained with respect to the relevant prescriptions of the recently established Italian building codes for seismic areas are also discussed. RÉSUMÉ Afin de contribuer à la discussion sur la validation des Eurocodes et des règlements parasismiques italiens pour les bâtiments, cet article se propose de montrer et d’examiner les résultats d’analyses de la réponse sismique locale menées par un modèle 1-D linéaire équivalent dans un certain nombre de ‘test sites’ bien documentés qui se trouvent le long de la côte adriatique, dans la ville de Senigallia (Italie centrale). En considérant aussi bien l’intensité moyenne-basse du séisme attendu dans la zone étudiée (pic d’accélération 0.20g sur formation rocheuse pour une période de retour de 475 ans) que les caractéristiques géomorphologiques du site, consistant principalement d’une Plio-Pléistocène roche-substratum marno-argileuse située en dessous de dépôts de plaine alluviale et de terrasses étagées où les effets 2-D n’ont pas d’influence, les analyses de la réponse sismique locale ont été menées par un modèle 1-D linéaire équivalent. L’étude a été effectué sur onze verticales où les propriétés dynamiques du terrain ont été soigneusement mesurées. Afin de limiter les incertitudes liées à la donnée sismique, on a employé des enregistrements sismiques réels comme des signaux sismiques simulés. Dans cet article sont présentés les résultats numériques des analyses; les spectres de réponse obtenus sont confrontés aux spectres établis par l’Eurocode 8 et par les récents règlements parasismiques italiens pour les correspondants types de sous-sol.

Dynamic Soil Properties and Site Coefficients for Aseismic Building Design in Some Typical Soil Deposits of the Marche Region, Italy

bstract— Although in Central Italy seismicity is lly moderate and the maximum expected local Richter tudes are about 6-6.5, in the past many urban ents and villages have experienced, even during low ity earthquakes, very severe damage, which can be ted to the sharp topography or the presence of thick ts or the particular dynamic properties of the soils. fore, in order to provide new updated guidelines for c building design, great research effort has been aimed quantification of site responses in various Italian ical centres over the latest years. Moreover, since ode 8 (EC8) will be adopted within a short period in ies of the European Union, these studies have also aimed at controlling reliability of EC8 spectra for sites. This paper describes the research developed for fects evaluation at Offida, a historical centre in The e with important monuments and environmental ge. A specific program of seismological investigations, ting in measuring low amplitude earthquakes and tremors, and geotechnical testing, including boreholes, ic field and laboratory tests, was carried out. A y of methods were utilised and compared, considering nt earthquake scenarios and ground motions. The ed spectra were finally compared with those proposed rocode 8.

Liquefaction Hazard Maps of the Harbour Area of Gioia Tauro (Italy) by Geo-Statistical Methods

This paper reports the results of a case study of liquefaction assessment and mapping carried out in the harbour area of Gioia Tauro, in the southern part of Italy. The area, lying on a flat plain prevalently constituted in the first 20 meters below the ground level by cohesionless loose soils, struck by several historical earthquakes with intensity superior to VIII MCS, was the object of extensive seismological, geological and geotechnical surveys. The cyclic resistance ratio and the liquefaction potential index were estimated from numerous but not equispatially distributed in the area CPT and SPT profiles. Therefore geo-statistical method were applied to draw up reliable liquefaction hazard maps including uncertainties of estimated risk.

Protezione sismica di alcuni centri di interesse storico culturale in Garfagnana : il caso di Castelnuovo Garfagnana

Seismic protection of historical urban nuclei in Garfagnana: an example Garfagnana region was repeatedly struck by destructive earthquakes up until quite recently. The region is mainly mountainous and very rocky, and is crossed by different systems of active faults. Many urban nuclei are situated on steep hillside and along deep valleys. The morphological and geotechnical conditions are favourable for producing topographic and stratigraphic amplification effects. The physical phenomena associated to these effects, generally disregarded in risk analyses on large scale and from the Italian seismic building code, have been object, in the last twenty years, of extensive research of the scientific community. The present research describes a few preliminary analyses for the site effects evaluation in the historical centre of Castelnuovo Garfagnana.

Investigation of the Seismic Soil-Structure Interaction on a Concrete Instrumental Building

SUMMARY Experience has shown that soil-structure interaction can play an important role on structural behaviour during earthquakes. A complete soil-structure interaction analysis consists of two parts: a site response analysis for free field motions and an interaction analysis for structural response. In the present study the effects of soil-structure interaction are evaluated on a two-storey concrete building about 10 m high with a rectangular horizontal section of about 11m x 28 m. The building, of public interest, is equipped with several accelerometers. The structure and the foundation system were idealised by a 3-D finite elements model, while the underlying soil is represented by a semi-infinite visco-elastic 1-D model. The soil-structure interaction analysis was performed by using the substructuring method implemented by the SASSI2000 numerical code. The accelerograms recorded during a low magnitude earthquake (ML = 4) by a free field seismic station, about 5m away from the building, were adopted as the seismic input motion. In this paper the results of the numerical analyses obtained in some significant nodes of the structure are presented both in time and frequency domain, and compared with the seismic recordings; moreover the influence of the structure on the ground motion is evaluated by comparing the free field actual motion with the numerical modelling results at the boundary between the soil and the foundation.