Dans cet article, on presente les resultats d'un certain nombre d'essais a long terme (en traction simple et en flexion) effectues sur quatre sortes de pierres naturelles utilisees tres souvent autrefois en Italie pour la... more
Dans cet article, on presente les resultats d'un certain nombre d'essais a long terme (en traction simple et en flexion) effectues sur quatre sortes de pierres naturelles utilisees tres souvent autrefois en Italie pour la construction (le marbre blanc de Carrara, deux sortes de gres, la pierre de Florence et la "Pietraforte", ainsi que sur la pierre calcaire de Piobbico-Cesana). Les essais ont ete realises en appliquant de facon continue aux eprouvettes differentes fractions de charges "instantanees" de rupture, en relevant l'evolution de la deformation jusqu'a la rupture. En general, tous les essais ont montre un comportement caracterise par les trois phases classiques du fluage. En meme temps, on a constate une diminution de 60 % de la resistance, tant a la traction qu'a la flexion, par rapport a une duree d'essais peu superieure a un an. Cet article presente un modele constitutif phenomenologique permettant d'analyser le comportement visco-plastique observe. On indique ici, en vue d'applications techniques, une fonction de fluage qui permet l'evaluation directe des effets de la diminution de la resistance mecanique. Enfin, on presente les resultats de l'identification effectuee pour l'etalonnage des parametres caracteristiques des lois analytiques qui reglent le modele constitutif. (A).
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The design analysis of a reinforced concrete building, seismically isolated at its base by a combined system of steel-teflon sliding bearings and silicone-fluid viscous spring-dampers, is reported in this paper. The influence of the... more
The design analysis of a reinforced concrete building, seismically isolated at its base by a combined system of steel-teflon sliding bearings and silicone-fluid viscous spring-dampers, is reported in this paper. The influence of the friction-like be-haviour of sliders on the global system response is initially examined, by exploiting the results of an experimental programme carried out to this aim within the European Community funded Research Project \u201cDISPASS\u201d. The application of a prelimi-nary design criterion, formulated in previous studies dedicated to this special protection strategy, is then presented. The damping coefficient of fluid viscous dissipaters capable of optimising the seismic response is particularly located by this cri-terion. A synthesis of the analyses developed by the finite element model of the structure is after-wards proposed. The performances obtained for the seismic action levels corresponding to the damage and ultimate limit states, according to the most recent Italian Standards (Ordinanza 3274) requirements, as well as to a third \u2013 so called maximum considered \u2013 earthquake level, are finally discussed
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Selected topics from structural studies carried out on the damped cable system are presented herein. This seismic protection technique has been the subject of a European Community-funded Research Project, recently completed, where it was... more
Selected topics from structural studies carried out on the damped cable system are presented herein. This seismic protection technique has been the subject of a European Community-funded Research Project, recently completed, where it was detailed, implemented, and assessed from analytical/numerical, experimental, architectural, and economic viewpoints. This allowed establishing the required scientific and technological basis for bringing the system to an industrial level. After a general framing of the system characteristics, this paper offers a demonstration of the on-site experimental section of the Project, developed on a full-scale mock-up retrofitted by damped cables. An example design of the system follows, with regards to the seismic rehabilitation of a medium-rise steel office building, representative of one of its preferential fields of application. Attainment of the enhanced performance objectives assumed in this design highlights the potentialities of damped cables as an advanced seismic-control strategy for framed structures
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A school building with reinforced concrete structure, seismically retrofitted in 2013 and damaged by the 2016 Central Italy earthquake, is examined in this paper. A time-history assessment analysis is initially carried out in... more
A school building with reinforced concrete structure, seismically retrofitted in 2013 and damaged by the 2016 Central Italy earthquake, is examined in this paper. A time-history assessment analysis is initially carried out in pre-rehabilitated conditions by simulating also the presence of the clay brick masonry infill perimeter walls and partitions in the finite element model of the structure. Based on the results of this analysis, a different retrofit solution is proposed, consisting in the incorporation of dissipative braces equipped with pressurized fluid viscous dampers. The verification analyses developed in this new configuration for the main shock records of the 2016 earthquake highlight slightly damaged and easily repairable response conditions of a little number of partitions — instead of the diffused moderate-to-severe damage surveyed in the building internal and perimeter infills— and an elastic response of structural members.
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A base isolation study on the advanced seismic retrofit of a reinforced concrete elevated water storage tank with shaft staging is presented in this paper. The tank was built in the late 1920s and is still in service. In consideration of... more
A base isolation study on the advanced seismic retrofit of a reinforced concrete elevated water storage tank with shaft staging is presented in this paper. The tank was built in the late 1920s and is still in service. In consideration of its historical significance, base isolation offers an optimal joined solution to the concurrent issues of a substantial seismic performance improvement and a virtually null architectural impact on the superstructure. The isolation system is constituted by a set of double curved sliding surface isolators placed below the cylindrical shaft staging wall. The incorporation of the protective system causes to modify the pressurized pipes delivering water to the tank and the discharge pipes too. Two different interventions are designed to this aim. The first one consists in installing an expansion joint with high lateral displacement capacity at the connection of the mobile (i.e. linked to the superstructure) and fixed (i.e. linked to the pump lying on the...
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A monolateral-friction element is specifically developed for modeling masonry structures. Its use in modeling masonry material and masonry structures is shown. In particular, the paper presents the proposed modeling technique together... more
A monolateral-friction element is specifically developed for modeling masonry structures. Its use in modeling masonry material and masonry structures is shown. In particular, the paper presents the proposed modeling technique together with some applications. The numerical results of the applications are compared to experimental results
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Background:The anti-seismic design of prefab reinforced concrete buildings is usually carried out with a conventional ductility-based approach. This implies a remarkable plastic demand on columns, as well as damages to the connections of... more
Background:The anti-seismic design of prefab reinforced concrete buildings is usually carried out with a conventional ductility-based approach. This implies a remarkable plastic demand on columns, as well as damages to the connections of structural and non-structural members, for seismic events with comparable intensity to the basic design earthquake normative level.Objective:In view of this, a study was developed and aimed at extending to the field of new prefab reinforced concrete structures the application of advanced seismic protection strategies, capable of guaranteeing undamaged response up to the maximum considered earthquake normative level.Method:A benchmark building was designed as demonstrative case study for this purpose, in the three following hypotheses: (a) according to a traditional ductility-based approach; (b) by incorporating dissipative bracings, equipped with fluid viscous dampers; (c) by placing a seismic isolation system at the base, composed of a set of doubl...
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Le ripetute scosse sismiche che dal 24 agosto 2016 al 18 gennaio 2017 hanno colpito numerose costruzioni ed agglomerati urbani del Centro-Italia sono state per essi un\u2019ennesima prova della loro vulnerabilit\ue0 sismica. Ci\uf2 \ue8... more
Le ripetute scosse sismiche che dal 24 agosto 2016 al 18 gennaio 2017 hanno colpito numerose costruzioni ed agglomerati urbani del Centro-Italia sono state per essi un\u2019ennesima prova della loro vulnerabilit\ue0 sismica. Ci\uf2 \ue8 valso anche per alcuni edifici pre-normativi che erano gi\ue0 stati sottoposti ad interventi di adeguamento per dissipazione supplementare di energia. La tecnica utilizzata non si \ue8 sempre rivelata rispondente alle attese di accrescimento di prestazione previste in fase di progetto, ribadendo l\u2019importanza della scelta della tipologia di dispositivo da utilizzare a tal fine. Tenendo conto di ci\uf2, nella memoria viene proposto lo studio dell\u2019efficacia dell\u2019impiego di un sistema di dissipazione supplementare di energia, realizzato mediante dispositivi preminentemente dissipativi fluido-viscosi a matrice siliconica, per l\u2019adeguamento di un edificio ad uso scolastico, danneggiato dal sisma del 30 ottobre 2016. Sito nel Comune di N...
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An overview of the structural studies carried out on the damped cable system within the Research and Technological Development European Project \u201cSPIDER\u201d is presented in this paper. The research activities developed by the Udine... more
An overview of the structural studies carried out on the damped cable system within the Research and Technological Development European Project \u201cSPIDER\u201d is presented in this paper. The research activities developed by the Udine University staff during the Project, mainly concerning analytical modelling, numerical/parameter investigations and the definition of design procedures, are particularly reported. As regards the last aspect, a complete design methodology is herein proposed for the first time, outside the special report to the European Commission in which it was originally formulated. Finally, selected results of the experimental campaign performed on a pilot full-scale building equipped with this innovative seismic protection technology, are summed up
A previously formulated assessment procedure of the seismic performance of historical and artistic buildings is herein applied to a representative example of the eighteenth-century noble-residence architecture in Tuscany. Differently from... more
A previously formulated assessment procedure of the seismic performance of historical and artistic buildings is herein applied to a representative example of the eighteenth-century noble-residence architecture in Tuscany. Differently from other examined case studies, where essentially elastic structural models had been used, the analysis of the current status of the building is carried out in this case by a non-linear smeared crack model. As a general result of the evaluation enquiry, no limitation relevant to the three postulated performance levels is met for the corresponding levels of seismic action. In order to substantially improve the response capacities of the building, an advanced seismic retrofit hypothesis is then formulated, which consists in a combined base isolation/supplemental damping technique obtained by coupling steel-teflon sliding bearings and silicone fluid viscous devices. Finally, this retrofit solution allows largely attaining the established performance objectives
Nell\\u2019articolo \\ue8 presentata una sintesi di alcuni risultati delle attivit\\ue0 condotte dall\\u2019Unit\\ue0 di ricerca di Udine, durante l\\u2019ultimo anno di svolgimento del programma della Linea 7, all\\u2019interno del... more
Nell\\u2019articolo \\ue8 presentata una sintesi di alcuni risultati delle attivit\\ue0 condotte dall\\u2019Unit\\ue0 di ricerca di Udine, durante l\\u2019ultimo anno di svolgimento del programma della Linea 7, all\\u2019interno del Progetto ReLUIS-DPC 2005/2008. \\uc8 inizialmente riportato un breve riepilogo degli studi pervenuti a definitivo compimento o ad una pi\\uf9 avanzata fase di maturazione durante quest\\u2019ultimo anno del Progetto, suddivisi per argomenti, con indicazione delle relative pubblicazioni redatte od apparse nel 2008. Successivamente, \\ue8 fatto riferimento al tema sin qui giunto ad una fase intermedia di sviluppo, e non ancora oggetto di comunicazioni scritte, riguardante l\\u2019analisi del martellamento sismico tra edifici contigui, e la sua mitigazione mediante l\\u2019impiego di dispositivi fluido-viscosi pressurizzati di produzione Jarret. Sono, inoltre, presentati alcuni risultati della campagna sperimentale condotta sulla struttura \\u201cJETPACS\\u201d, presso il Laboratorio Prove e Strutture dell\\u2019Universit\\ue0 della Basilicata, in presenza di controventi dissipativi includenti tale tipologia di dispositivi
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L\u2019articolo presenta una sintesi degli studi condotti dagli autori riguardo all\u2019applicazione dell\u2019isolamento sismico ad allestimenti permanenti e temporanei di oggetti d\u2019arte. Dopo un iniziale cenno a significative... more
L\u2019articolo presenta una sintesi degli studi condotti dagli autori riguardo all\u2019applicazione dell\u2019isolamento sismico ad allestimenti permanenti e temporanei di oggetti d\u2019arte. Dopo un iniziale cenno a significative realizzazioni di letteratu-ra, viene riassunta la procedura di valutazione della prestazione sismica dei manu-fatti formulata nei suddetti studi, unitamente alla strategia di protezione proposta, consistente nell\u2019isolamento di interi solai su cui insiemi di oggetti debbano essere collocati, in alternativa all\u2019isolamento di ciascuno di essi singolarmente. Sono infine richiamati alcuni risultati relativi a tre sculture di assai differenziate caratteristiche materiali, geometriche e dinamiche
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Observation of damage caused by recent earthquakes highlights, once again, that the presence of infills significantly affects the seismic response of reinforced concrete (R.C.) frame buildings. Therefore, in spite of the fact that infills... more
Observation of damage caused by recent earthquakes highlights, once again, that the presence of infills significantly affects the seismic response of reinforced concrete (R.C.) frame buildings. Therefore, in spite of the fact that infills are non-structural elements, and thus they are normally not considered in structural analyses, in many cases their contribution should not be neglected. Based on these observations, the study proposed in this paper consists in the evaluation of the seismic response of infills in time-history finite element analyses of R.C. frame structures by means of a two-element model, constituted by two diagonal nonlinear beams. A “concrete”-type hysteretic model predicts the in-plane state of infills, through a force-displacement backbone curve expressly generated, and scanned in terms of performance limits, to this aim. This model is demonstratively applied to a real case study, i.e. a R.C. frame building including various types of brick masonry perimeter inf...
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Supplemental damping strategies are increasingly adopted for seismic retrofit of frame structures also in consideration of their low-impact architectural and environmental characteristics. A further spreading of these technologies in the... more
Supplemental damping strategies are increasingly adopted for seismic retrofit of frame structures also in consideration of their low-impact architectural and environmental characteristics. A further spreading of these technologies in the professional community strongly depends on the availability of simple design procedures, especially concerning the preliminary sizing of the dissipaters. A viable design criterion was recently proposed by the author to this aim and applied to the retrofit study of a reinforced concrete gym buiding. A new case study, namely a school building in Florence dating back to the early 1980s, is examined in this paper, so as to evaluate the feasibility of the criterion for a more complex structure. The building is composed of two portions, with reinforced concrete and steel frame structure, respectively. Similarly to several other buildings of the same period, the structure is infilled by heavy reinforced concrete panels interacting with the frame elements u...
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The effects of simulated near-fault earthquakes on the response of base-isolated structures are analysed in this paper. Two types of physically realisable near-source ground motion models were examined in this study, both represented by... more
The effects of simulated near-fault earthquakes on the response of base-isolated structures are analysed in this paper. Two types of physically realisable near-source ground motion models were examined in this study, both represented by trigonometric \u201cforward and back\u201d pulses produced by a blind-thrust fault. The base isolation system considered was a special technology coupling steel-Teflon sliding bearings and silicone fluid-viscous dampers. The following analyses were carried out: a) evaluation of the spectral response of SDOF oscillators, incorporating the technology above, to the two types of simulated pulses; b) comparison of the resulting spectra with the corresponding curves derived from artificial accelerograms generated from the design spectrum of the Italian seismic Standards; c) application of the most critical near-fault signals highlighted by the spectral analysis to the computational model of an actual base-isolated building. A report on these analyses is pr...
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Seismic tests have been conducted on two 3-storey buildings protected with fluid-viscous spring damper devices. One of the buildings was a reinforced concrete frame with clay elements in the slabs, while the other one was a steel frame... more
Seismic tests have been conducted on two 3-storey buildings protected with fluid-viscous spring damper devices. One of the buildings was a reinforced concrete frame with clay elements in the slabs, while the other one was a steel frame with steel/concrete composite slabs. The spring dampers were installed through K bracing in between the floors. The tests were performed by means of the pseudodynamic method on full-size specimens and by implementing a specific compensation strategy for the strain-rate effects at the devices. The tests results allowed to compare the behaviour of the unprotected buildings with several protected configurations showing the benefits of the application of the devices and the characteristics of their behaviour
The main results of a testing campaign carried out on a large-scale steel frame, seismically improved by the incorporation of bracing members equipped with fluid viscous dampers, are reported herein. This investigation is part of the... more
The main results of a testing campaign carried out on a large-scale steel frame, seismically improved by the incorporation of bracing members equipped with fluid viscous dampers, are reported herein. This investigation is part of the European Community-funded Research Programme DISPASS, dedicated to the experimental verification of several innovative seismic protection technologies. The tests were performed by the continuous pseudo-dynamic test method implemented at the ELSA Laboratory of the Joint Research Centre \u2013 Ispra. This campaign substantially validated a special energy-based design criterion, formulated in previous phases of this research, which was applied to determine the damping properties of the dissipaters installed on the test structure. Moreover, the analytically evaluated capacities of damped braces for mitigating the seismic demand on the examined frame were totally confirmed by the experiments, through a direct comparison with the response obtained in unprotec...
A study focused on the application of passive seismic control strategies to the field of new prefab R/C structures is presented herein. A benchmark building was designed to the purpose, assuming the typical geometrical layout and... more
A study focused on the application of passive seismic control strategies to the field of new prefab R/C structures is presented herein. A benchmark building was designed to the purpose, assuming the typical geometrical layout and dimensions of single-hall industrial buildings in Italy, which are also similar to the characteristics of the same class of buildings in other countries of the Mediterranean area. The design was carried out in the three following hypotheses: (a) according to a traditional ductility-based approach; (b) by incorporating dissipative bracings, equipped with fluid viscous dampers; (c) by placing a seismic isolation system at the base, composed of a set of double curved surface sliders. The earthquake and performance levels assumed, their relevant limitations, the design criteria and the technical installations of the three solution are discussed in detail. A comparison of relevant sizes, seismic performance and costs is finally presented
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A synthesis of a non-linear finite element structural assessment enquiry carried out on a monumental modern heritage building is reported in this paper. The study includes a buckling analysis of the slender steel beams constituting a... more
A synthesis of a non-linear finite element structural assessment enquiry carried out on a monumental modern heritage building is reported in this paper. The study includes a buckling analysis of the slender steel beams constituting a mushroom-type roof, and an ―integral‖ seismic pushover analysis of the supporting R/C columns. The computational solutions obtained for the steel roof beams are compared to the results derived from a calculation of the critical stress of beam panels, and the global lateral-torsional buckling resistance of members developed according to the Technical Standards adopted for structural verifications. The unconventional ―full-cracking‖ pushover application to the R/C columns offers detailed simulation of the evolution of their non-linear response, which is discussed in the paper, along with the most significant parameter and procedure choices made in the analysis.
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Abstract Pre-normative elevated liquid storage tanks with reinforced concrete (R/C) frame staging are among the most seismically vulnerable structures in urban areas, due to their unfavourable earthquake-resistant configuration. A... more
Abstract Pre-normative elevated liquid storage tanks with reinforced concrete (R/C) frame staging are among the most seismically vulnerable structures in urban areas, due to their unfavourable earthquake-resistant configuration. A representative case study, i.e. a R/C water tower designed by the world-famous Italian engineer Pier Luigi Nervi and built in the early 1930s, is examined herein. The assessment of the structure was developed with a detailed finite element model, which includes a multi spring-mass assembly to reproduce the fluid–tank dynamic interaction. The time-history evaluation analysis, initially carried out by assuming an elastic behavior of the staging members, showed general unsafe response conditions of beams and columns under seismic action scaled at the maximum considered earthquake (MCE) level. These results were confirmed at a second step of the analysis, where the plastic behavior of beams and columns was investigated after incorporating lumped plastic hinges at their end sections, which resulted in the collapse of the model. Based on these data, two passive energy dissipation-based retrofit measures were proposed, for which dissipative bracing systems incorporating either pressurized fluid viscous spring-dampers or added damping and stiffness steel yielding devices, respectively, were installed. The two systems were designed with a mutual energy-based criterion and for the same target performance objectives, that is, reaching elastic response up to the MCE. The benefits induced by the two protective systems to the seismic response of the tank structure are discussed, and the geometrical dimensions and relevant architectural impact are compared with the ones of a conventional non-dissipative bracing retrofit solution developed for the same performance.
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Abstract Pre-normative elevated liquid storage tanks with reinforced concrete (R/C) frame staging are among the most seismically vulnerable structures in urban areas, due to their unfavourable earthquake-resistant configuration. A... more
Abstract Pre-normative elevated liquid storage tanks with reinforced concrete (R/C) frame staging are among the most seismically vulnerable structures in urban areas, due to their unfavourable earthquake-resistant configuration. A representative case study, i.e. a R/C water tower designed by the world-famous Italian engineer Pier Luigi Nervi and built in the early 1930s, is examined herein. The assessment of the structure was developed with a detailed finite element model, which includes a multi spring-mass assembly to reproduce the fluid–tank dynamic interaction. The time-history evaluation analysis, initially carried out by assuming an elastic behavior of the staging members, showed general unsafe response conditions of beams and columns under seismic action scaled at the maximum considered earthquake (MCE) level. These results were confirmed at a second step of the analysis, where the plastic behavior of beams and columns was investigated after incorporating lumped plastic hinges at their end sections, which resulted in the collapse of the model. Based on these data, two passive energy dissipation-based retrofit measures were proposed, for which dissipative bracing systems incorporating either pressurized fluid viscous spring-dampers or added damping and stiffness steel yielding devices, respectively, were installed. The two systems were designed with a mutual energy-based criterion and for the same target performance objectives, that is, reaching elastic response up to the MCE. The benefits induced by the two protective systems to the seismic response of the tank structure are discussed, and the geometrical dimensions and relevant architectural impact are compared with the ones of a conventional non-dissipative bracing retrofit solution developed for the same performance.
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ABSTRACT