Hybrid simulation of a multi‐span RC viaduct with plain bars and sliding bearings          下载免费PDF全文

Giuseppe Abbiati  Oreste S. Bursi  Philippe Caperan  Luigi Di Sarno  Francisco Javier Molina  Fabrizio Paolacci  Pierre Pegon 《地震工程与结构动力学》2015,44(13):2221-2240

This paper deals with the seismic response assessment of an old reinforced concrete viaduct and the effectiveness of friction‐based retrofitting systems. Emphasis was laid on an old bridge, not properly designed to resist seismic action, consisting of 12 portal piers that support a 13‐span bay deck for each independent roadway. On the basis of an OpenSEES finite element frame pier model, calibrated in a previous experimental campaign with cyclic displacement on three 1:4 scale frame piers, a more complex experimental activity using hybrid simulation has been devised. The aim of the simulation was twofold: (i) to increase knowledge of non‐linear behavior of reinforced concrete frame piers with plain steel rebars and detailing dating from the late 1950s; and (ii) to study the effectiveness of sliding bearings for seismic response mitigation. Hence, to explore the performance of the as built bridge layout and also of the viaduct retrofitted with friction‐based devices, at both serviceability and ultimate limit state conditions, hybrid simulation tests were carried out. In particular, two frame piers were experimentally controlled with eight‐actuator channels in the as built case while two frame piers and eight sliding bearings were controlled with 18‐actuator channels in the isolated case. The remaining frame piers were part of numerical substructures and were updated offline to accurately track damage evolution. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Time-dependent geochemistry of clinopyroxene from the Alban Hills (Central Italy): Clues to the source and evolution of ultrapotassic magmas     

Mario Gaeta  Carmela Freda  John N. Christensen  Luigi Dallai  Fabrizio Marra  Daniel B. Karner  Piergiorgio Scarlato 《Lithos》2006,86(3-4):330-346

We investigated chemical and isotopic compositions of clinopyroxene crystals from well age-constrained juvenile scoria clasts, lava flows, and hypoabyssal magmatic ejecta representative of the whole eruptive history of the Alban Hills Volcanic District. The Alban Hills is a Quaternary ultra-potassic district that was emplaced into thick limestone units along the Tyrrhenian margin of Italy. Alban Hills volcanic products, even the most differentiated, are characterised by low SiO₂ content. We suggest that the low silica activity in evolving magmas can be ultimately due to a decarbonation process occurring at the magma/limestone interface. According to the liquid line of descent we propose, the differentiation process is driven by crystallisation of clinopyroxene + leucite ± apatite ± magnetite coupled with assimilation of a small amount of calcite and/or with interaction with crustal CO₂. By combining age, chemical data, strontium and oxygen isotopic compositions, and REE content of clinopyroxene, we give insights into the evolution of primitive ultrapotassic magmas of the Alban Hills Volcanic District over an elapsed period of about 600 kyr. Geochemical features of clinopyroxene crystals, consistent with data coming from other Italian ultrapotassic magmas, indicate that Alban Hills primary magmas were generated from a metasomatized lithospheric mantle source. In addition, our study shows that the ⁸⁷Sr / ⁸⁶Sr and LREE/HREE of Alban Hills magmas continuously diminished during the 600–35 ka time interval of the Alban Hills eruptive history, possibly reflecting the progressive depletion of the metasomatized mantle source of magmas.  相似文献   

PAOLO: A Polarimeter Add‐On for the LRS Optics at a Nasmyth focus of the TNG     

S. Covino  E. Molinari  P. Bruno  M. Cecconi  P. Conconi  P. D'Avanzo  L. di Fabrizio  D. Fugazza  M. Giarrusso  E. Giro  F. Leone  V. Lorenzi  S. Scuderi 《Astronomische Nachrichten》2014,335(2):117-123

We describe a new polarimetric facility available at the Istituto Nazionale di AstroFisica / Telescopio Nazionale Galileo at La Palma, Canary islands. This facility, PAOLO (Polarimetric Add‐On for the LRS Optics), is located at a Nasmyth focus of an alt‐az telescope and requires a specific modeling in order to remove the time‐ and pointing position‐dependent instrumental polarization. We also describe the opto‐mechanical structure of the instrument and its calibration and present early examples of applications. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Connectivity and single/dual domain transport models: tests on a point-bar/channel aquifer analogue     

Diana Dell’Arciprete  Chiara Vassena  Fulvia Baratelli  Mauro Giudici  Riccardo Bersezio  Fabrizio Felletti 《Hydrogeology Journal》2014,22(4):761-778

In porous aquifers, groundwater flow and solute transport strongly depend on the sedimentary facies distribution at fine scale, which determines the heterogeneity of the conductivity field; in particular, connected permeable sediments could form preferential flow paths. Therefore, properly defined statistics, e.g. total and intrinsic facies connectivity, should be correlated with transport features. In order to improve the assessment of the relevance of this relationship, some tests are conducted on two ensembles of equiprobable realizations, obtained with two different geostatistical simulation methods—sequential indicator simulation and multiple point simulation (MPS)—from the same dataset, which refers to an aquifer analogue of sediments deposited in a fluvial point-bar/channel association. The ensembles show different features; simulations with MPS are more structured and characterised by preferential flow paths. This is confirmed by the analysis of transport connectivities and by the interpretation of data from numerical experiments of conservative solute transport with single and dual domain models. The use of two ensembles permits (1) previous results obtained for single realizations to be consolidated on a more firm statistical basis and (2) the application of principal component analysis to assess which quantities are statistically the most relevant for the relationship between connectivity indicators and flow and transport properties.  相似文献   

Deconstructing Italy: (Northern) Italians and their new perception of territoriality     

Fabrizio Eva 《GeoJournal》1999,48(2):101-107

The nineties will go down in Italian history as the decade of great political change. By way of emphasising this change, the media and politicians use the expressions `Prima Repubblica' and `Seconda Repubblica' (first and second republics), adopting the terminology used by the French for their `republics'. During the so-called First Republic (1948–1994), the centrist Christian Democrat Party represented the moderate political force in every government. However, the corruption trials of 1992–1993, which involved many of this party's members, led to its collapse at the ballot box. In northern Italy, a consequence of the demise of the Christian Democrats was the resounding success of the Lega Nord at the local government elections of 1993 and the general election of 1994. The Lega Nord based, and continues to base, its success on the use of ethno-nationalist slogans and catchcries. Italy has an ancient tradition – dating at least from the fall of the Roman Empire – of political and linguistic splintering. Given today's situation, this factor may have impacts at the level of the structure of the state: federalism, special statutes for regions and/or provinces, the decentralization of the state, and so on. For the first time for perhaps more than a century, in this new period of uncertain political change, Italians are increasingly viewing territory and its characteristics as politically relevant. Justifications for `national' cohesion are being rediscovered, or invented, at the local level, transforming it into political claims. Italians have begun to talk about relationships with territories and neighbouring groups from a different perspective. At present, traditional political parties and politicians are too slow and insufficiently focused in their response to the rising call for autonomy and decision-making authority at the local level. This factor has provided the time and space for isolationist and culturally self-reliant localist ideologies to propagate. It is impossible to say how long this period of transition will last and what its outcomes will be. The three main choices now facing Italians would be appear to be:(1) reclaim the nationalist sentiment of a united state (abandoned after the Fascist era);(2) provide the space (ideological and territorial) for the numerous localist nationalisms;(3) construct a real and flexible `localist' democracy for Italy as a whole.  相似文献   

Low-magnitude earthquakes in Rome: structural interpretation and implications for the local stress field     

Fabrizio Marra 《Geophysical Journal International》1999,138(1):231-243

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Evaluation of liquefaction potential in an intermountain Quaternary lacustrine basin (Fucino basin,central Italy)     

Paolo Boncio  Sara Amoroso  Giovanna Vessia  Marco Francescone  Mauro Nardone  Paola Monaco  Daniela Famiani  Deborah Di Naccio  Alessia Mercuri  Maria Rosaria Manuel  Fabrizio Galadini  Giuliano Milana 《Bulletin of Earthquake Engineering》2018,16(1):91-111

In this study, we analyse the susceptibility to liquefaction of the Pozzone site, which is located on the northern side of the Fucino lacustrine basin in central Italy. In 1915, this region was struck by a M 7.0 earthquake, which produced widespread coseismic surface effects that were interpreted to be liquefaction-related. However, the interpretation of these phenomena at the Pozzone site is not straightforward. Furthermore, the site is characterized by an abundance of fine-grained sediments, which are not typically found in liquefiable soils. Therefore, in this study, we perform a number of detailed stratigraphic and geotechnical investigations (including continuous-coring borehole, CPTu, SDMT, SPT, and geotechnical laboratory tests) to better interpret these 1915 phenomena and to evaluate the liquefaction potential of a lacustrine environment dominated by fine-grained sedimentation. The upper 18.5 m of the stratigraphic succession comprises fine-grained sediments, including four strata of coarser sediments formed by interbedded layers of sand, silty sand and sandy silt. These strata, which are interpreted to represent the frontal lobes of an alluvial fan system within a lacustrine succession, are highly susceptible to liquefaction. We also find evidence of paleo-liquefaction, dated between 12.1–10.8 and 9.43–9.13 kyrs ago, occurring at depths of 2.1–2.3 m. These data, along with the aforementioned geotechnical analyses, indicate that this site would indeed be liquefiable in a 1915-like earthquake. Although we found a broad agreement among CPTu, DMT and shear wave velocity “simplified procedures” in detecting the liquefaction potential of the Pozzone soil, our results suggest that the use and comparison of different in situ techniques are highly recommended for reliable estimates of the cyclic liquefaction resistance in lacustrine sites characterized by high content of fine-grained soils. In geologic environments similar to the one analysed in this work, where it is difficult to detect liquefiable layers, one can identify sites that are susceptible to liquefaction only by using detailed stratigraphic reconstructions, in situ characterization, and laboratory analyses. This has implications for basic (Level 1) seismic microzonation mapping, which typically relies on the use of empirical evaluations based on geologic maps and pre-existing sub-surface data (i.e., age and type of deposits, prevailing grain size, with particular attention paid to clean sands, and depth of the water table).  相似文献   

Seismic response prediction of reinforced concrete buildings through nonlinear combinations of intensity measures     

Alessandra Fiore  Fabrizio Mollaioli  Giuseppe Quaranta  Giuseppe C. Marano 《Bulletin of Earthquake Engineering》2018,16(12):6047-6076

A widespread approach for the prediction of the structural response as function of the ground motion intensity is based on the Cloud Analysis: once a set of points representing the engineering demand parameter (EDP) values is obtained as function of the selected seismic intensity measure (IM) for a collection of unscaled earthquake records, a regression analysis is performed by assuming a specific functional form to correlate these variables. Within this framework, many studies have been devoted so far to evaluate the effectiveness of several IMs in estimating the EDPs through intrinsically linear functional forms, but it is still unknown to what extent the use of the linear regression analysis affects the quality of the final results. This paper is intended to provide an answer to such question by means of the calibration of suitable nonlinear combinations of scalar IMs, whose statistical performances are compared with those obtained by using the functional form usually adopted for linear regression-based calibrations. Specifically, the Evolutionary Polynomial Regression technique is adopted to calibrate nonlinear regression models for the prediction of maximum inter-story drift ratio and maximum floor acceleration. The comparative analysis is performed for fixed-base and base-isolated reinforced concrete buildings subjected to ordinary or pulse-like ground motion taking into account accuracy, complexity, efficiency and sufficiency. Final results demonstrate that the linear regression analysis is suitable for fixed-base reinforced concrete buildings, but nonlinear regression models provide better estimates. On the other hand, the linear regression analysis can introduce a significant bias in the seismic response prediction of base-isolated buildings, and nonlinear regression models are deemed more appropriate.  相似文献   

Improved risk‐targeted performance‐based seismic design of reinforced concrete frame structures          下载免费PDF全文

Paolo Franchin  Francesco Petrini  Fabrizio Mollaioli 《地震工程与结构动力学》2018,47(1):49-67

This paper presents a procedure for seismic design of reinforced concrete structures, in which performance objectives are formulated in terms of maximum accepted mean annual frequency (MAF) of exceedance, for multiple limit states. The procedure is explicitly probabilistic and uses Cornell's like closed‐form equations for the MAFs. A gradient‐based constrained optimization technique is used for obtaining values of structural design variables (members' section size and reinforcement) satisfying multiple objectives in terms of risk levels. The method is practically feasible even for real‐sized structures thanks to the adoption of adaptive equivalent linear models where element‐by‐element stiffness reduction is performed (2 linear analyses per intensity level). General geometric and capacity design constraints are duly accounted for. The procedure is applied to a 15‐storey plane frame building, and validation is conducted against results in terms of drift profiles and MAF of exceedance, obtained by multiple‐stripe analysis with records selected to match conditional spectra. Results show that the method is suitable for performance‐based seismic design of RC structures with explicit targets in terms of desired risk levels.  相似文献   

Global Research Patterns on Ground Penetrating Radar (GPR)     

Fabrizio Terenzio Gizzi  Giovanni Leucci 《Surveys in Geophysics》2018,39(6):1039-1068

The article deals with the analysis of worldwide research patterns concerning ground penetrating radar (GPR) during 1995–2014. To do this, the Thomson Reuters’ Science Citation Index Expanded (SCI-EXPANDED) and the Social Sciences Citation Index accessed via the Web of Science Core Collection were the two bibliographic databases taken as a reference. We pay attention to the document typology and language, the publication trend and citations, the subject categories and journals, the collaborations between authors, the productivity of the authors, the most cited articles, the countries and the institutions involved, and other hot issues. Concerning the main research subfields involving GPR use, there were five, physical–mathematical, sedimentological–stratigraphical, civil engineering/engineering geology/cultural heritage, hydrological (HD), and glaciological (GL), subfields.  相似文献