1,720,975 research outputs found
Assigning the macroseismic vulnerability classes to strengthened ordinary masonry buildings: An update from extensive data of the 2016 Central Italy earthquake
No full textDamage scenarios caused by the 2016 Central Italy earthquake confirmed the relevant role of interventions on masonry buildings’ seismic performance, also by increasing (rather than reducing) their vulnerability. Notwithstanding, current literature procedures aimed at assigning to buildings an European Macroseismic Scale 1998 (EMS-98) vulnerability class (A to F) do not consider such influence especially referring to the several intervention techniques applied to masonry buildings since the 1980s in Italy. This impaired a proper matching of vulnerability classes to the real performances, as strengthened buildings are conventionally assigned to average vulnerability conditions (class C). In the present work, vulnerability classes are appropriately assigned to buildings in strengthened conditions, basing on the analysis of 2264 dwellings placed in 19 settlements. Inspections were carried out with a purposely developed rapid visual screening procedure. A performance-based definition of structural types considered a building's masonry quality, diaphragms' stiffness, and kind of interventions graded between downgrading and upgrading. Types with the same behaviour were grouped into vulnerability classes, in the full range from A to D, through a literature model compatible with the EMS-98. Rubble stone buildings with downgrading or worsening interventions behaved like those in original conditions (class A), whereas improved buildings typically performed like class C. Upgrading interventions led to class D, similarly to modern clay block buildings. Masonry quality influenced the classification more than diaphragms' stiffness. The empirical membership of each type to vulnerability classes was obtained, that which allowed to include variously strengthened masonry buildings within the EMS-98 framework
Intervention strategies for the seismic improvement of masonry buildings based on FME validation: The case of a terraced building struck by the 2016 central italy earthquake
Get PDFResidential masonry buildings represent a large stock among highly vulnerable structures in medium–high seismic hazard areas, often built without any anti-seismic provisions. Their rehabilitation and/or strengthening according to optimised intervention strategies is topical and may contribute to revaluating zones characterized by depopulation phenomena. In this paper, a terraced building struck by the 2016 Central Italy earthquake is analysed through a frame by macro element (FME) model. The building is composed of six two-storey units made of stone and clay block masonry walls and semi-rigid diaphragms. The numerical model was calibrated based on the damage pattern caused by the earthquake and then used to carry out parametric analyses on the strengthened conditions by simulating both one unit and the entire terrace. The effects of interventions applied to either vertical or horizontal components, both singularly and in combination, were analysed in terms of nonlinear static analyses, and quantified by a performance factor, according to the upgraded seismic code in Italy. Kinematic analyses also completed the assessment of the building. Results compared the capacity of interventions in attaining the targets defined for improvement at both local and overall levels
Seismic response of masonry buildings in historical centres struck by the 2016 Central Italy earthquake. Calibration of a vulnerability model for strengthened conditions
Get PDFBrought to light by the 1997 Umbria-Marche (Italy) earthquake for the first time, the theme of damage patterns of masonry buildings with structural interventions became urgent again in the 2016–17 Central Italy seismic swarm. On a sample of 2306 buildings within the seismic field, the 85% bears the signs of structural interventions. With the aim of inferring the vulnerability factors from damage of strengthened buildings, a close-up analysis revealed that interventions can cause damage to the structures on which they are applied because of i) poor detailing and ii) incompatibility among parts, old and new. These conditions limited the attainment of a building's box-like behaviour and, therefore, an unfavourable contribution of interventions was identified. Conversely, a favourable contribution was determined. The analytic comparison between the behaviour of building types with interventions and that of the vulnerability classes of the European Macroseismic Scale (EMS-98) obtained a vulnerability model for empirical data. Buildings whose interventions had an unfavourable contribution are comparable with ‘original’, unreinforced ones; conversely, a favourable contribution permitted them to approach the behaviour of modern masonry structures. This work represents a first step towards the inclusion of strengthened buildings in the EMS-98 vulnerability system
Gli effetti del consolidamento strutturale nel tessuto edilizio minore: alcune riflessioni a valle del sisma Centro Italia 2016
No full textFive years after the 2016 Central Italy earthquake, the debate on how to rebuild historical centres is still open and topical. Those centres are the result of recurring reconstruction processes following seismic events. The latest one gave the chance to question the effectiveness of structural interventions applied to masonry buildings in the last forty years. Nowadays, seismic codes upgraded the safety levels to be reached; conversely, intervention protocols aimed at preserving a building’s structural and aesthetical identity are still lacking.
In this study, based on onsite inspections of the 2016 seismic area, the authors propose five categories of residential masonry buildings, which refer to various combinations of structural interventions. Each category was evaluated in terms of appearance and structure preservation, and structural safety level. Their behaviour during the earthquake demonstrated the inadequacy of incompatible concrete tampering, whereas overall interventions led to satisfactorily performances. The best behaviour was reached by dwellings rebuilt with new materials, questioning the opportunity to apply this technique to the detriment of a centre’s historical identity
A Comparison Between Empirical Procedures for the Definition of Vulnerability Classes of Masonry Buildings: Application to Five Historical Centres Struck by 2016 Central Italy Earthquake
Get PDFThe definition of seismic risk scenarios necessarily depends on the attribution of a
vulnerability class to each building of a stock. In the macroseismic scale (EMS-98) the
vulnerability class – from A to F – results from the combination between horizontal and vertical
structures. On the basis of post-event surveys carried out in Italy after the earthquakes occurred
in the last 50 years, many rules for converting the masonry quality and the stiffness of horizontal
diaphragms into a vulnerability class have been proposed. However, despite the now high
number of retrofitted or strengthened buildings in Italy, structural interventions are not
mentioned in these procedures, except for metal tie rods and r.c. tie beams.
The paper proposes a critical approach to the definition of vulnerability classes, by the means
of applying the conversion rules to the same sample of 525 masonry buildings located in five
historical centres struck by 2016 Central Italy earthquake: Acquasanta Terme, Campi Alto di
Norcia, Castelsantangelo sul Nera, Muccia and Vezzano. They have been chosen due to the
extensive strengthening campaigns that had been carried out after earlier seismic events. The
preliminary recognition of the structural features of each building happens at the terms of the
MUSE-DV Masonry, a rapid visual screening procedure recently proposed by the authors.
The damage probability matrices (DPMs), obtained from each conversion, are compared to
those from a theoretical model proposed for the EMS-98. Given the same poor masonry quality,
the existing rules classify buildings in class A or B depending only on floors’ stiffness and
horizontal connections. As a result, both low and high damage may appear in the same
vulnerability class causing a bimodal trend in the damage distributions. Conversely, the
MUSE-DV procedure allows to reduce these two frequency peaks by considering interventions.
In fact, overall interventions, even on very poor masonry structures, may lead to a very low
damage and, consequently, to low vulnerability classes (even C or D), while uncontrolled
interventions could obtain a high damage and a high vulnerability. The twofold consequence is
that a) structural interventions have a ‘relative’, i.e. positive or negative, contribution; b) the
usual limitation to A and B vulnerability classes for random masonry buildings needs to be
widened to better explain the damage observed in the 2016 Central Italy earthquake
Equivalent frame modelling of an unreinforced masonry building in finite element environment
No full textEquivalent frame method (EFM) is a viable modelling option for global seismic analysis of masonry buildings in comparison to more refined techniques, such as finite elements (FE), especially in professional practice [1–3]. EFM takes advantage of a building’s geometric regularity, both in plan and elevation, as well as of the good quality of masonry and floors stiffness, as required for the activation of box-like behaviour under seismic loads. However, typical vulnerabilities in existing unreinforced masonry (URM) buildings, e.g. highly flexible floors, openings too close one another, poor quality masonry, isolated pillars or non-vertically aligned walls, limit the effectiveness of EFM application. Recently, many studies have been devoted to expanding the possibilities of applying EFM to buildings which do not meet box-behaviour hypotheses [4–6]. The paper describes the procedure for implementing an EF model of an existing URM building in Midas GEN, a FE software commonly used for design of steel and r.c. structures. The equivalent frame (piers and spandrels) consists of a system of mono-dimensional, lumped plasticity beam elements [7]. In MIDAS, the frame is defined by the user, who also have to control the modelling process, by using the theoretical criteria available [8–10] and adapting their results to a building’s characteristics. Therefore, some peculiar vulnerabilities of the original building may be specifically implemented, thus obtaining a more refined model. The case study is Palazzo Carraro, a cultural heritage building, located close to the old town of Noale (Venezia). The palace complies with the main requirements of EFM except for floors stiffness, although horizontal connections may be considered sufficient at this level of analysis. Pro and cons of the specific procedure are here discussed, also referring to other state-of-the-art techniques, such as continuum models [11] implemented through the DIANA FEA code. Finally, the work explores the response of the EF model to different modelling choices, but also its reliability in overall analyses
La modellazione informativa (HBIM) e il percorso di conoscenza degli edifici storici ed esistenti: applicazione e problemi in una villa veneta
No full textConservation projects on architectural heritage (AH) must rely on a wide range of data from various sources and disciplines, necessitating collaboration among experts and yielding multiple outputs.
Building information modelling (BIM) was initially designed to address the complexities of the construction sector, but unique characteristics of architectural heritage (HBIM), including traditional construction techniques, material decay, and damage, pose challenges to its application. Nevertheless, HBIM holds promise as a valuable tool for documenting and managing architectural heritage. The preliminary study of AH involves a series of steps, encompassing archival research and onsite material testing, with the goal of creating a model for assessing structural safety. This paper employs a similar approach to develop a BIM model of a Palladian villa in Vicenza, fully utilizing parametric modelling and the information embedded within 3D elements to convey the knowledge acquired during the study. As a result, the model is somewhat simplified; for example, the walls are represented as perfectly vertical. However, the lack of finer detail is compensated for by including corresponding information in the parameters of BIM objects (e.g., utilizing an ‘out-of-plumb’ parameter in this case). The stratigraphy of attributes elements was adapted to match that observed on site and therefore the walls were subdivided according to changes into materials, building phases and thickness, to display them correctly and allow further analysis. The mapping of the decay of materials required some redundancy, as decay information must be attributed also to the supporting elements. Overall, the BIM database proved flexible enough to gather all necessary information. However, the distribution of the model is hindered by user-defined attributes, which are still absent from shared libraries in the architectural heritage field
Local mechanism analysis in unreinforced masonry buildings according to a new procedure based on floor spectra evaluation
No full textLocal rather than global seismic behaviour is a well-known feature in both masonry aggregates
and monumental buildings with large internal spans, such as churches or palaces. In such cases safety assessment through local mechanisms kinematic analysis is generally considered a viable solution. However, the
definition of the seismic forces acting on secondary architectural elements (pinnacles, upper portions of facades, turrets, etc.) or masonry macroblocks, which may interact dynamically with the main structure, is not
banal.
Therefore, the recent update of Italian seismic code stresses the role of a building’s global dynamic response
and floors’ stiffness in the evaluation of seismic actions on the macroblocks in which it can be subdivided.
This result in a complete new definition of floor spectra which are strongly dependent on the dynamic parameters (damping, frequencies) of both, the building and the local mechanism, which also change at the different
limit states.
The paper aims at the implementation of the new procedures in an existing unreinforced masonry building
(Palazzo Carraro in Noale – Venice) with flexible horizontal diaphragms. Modal analysis is used to detect the
possible local mechanism and its results are compared to the evidence of the visual inspection of vulnerability
factors, showing some correspondence. Safety evaluations, in linear and non-linear field, according to the
previous and the current Italian seismic codes are carried out and compared. For the case study, the new procedure is much more pejorative, since acceleration and displacement demands are more than twice the ones
obtained in the old one
Aggiornamento ed ottimizzazione di strumenti schedografici multi-livello per il rilievo del danno e della vulnerabilità di edifici esistenti in muratura oggetto di interventi pregressi in zona sismica
No full textGli edifici in muratura dei centri storici ricadono spesso nelle categorie a più elevata vulnerabilità sismica, a causa di tipici aspetti costruttivi (es. l’irregolarità) e di debolezze intrinseche (degrado dei materiali, mancanza o inefficacia delle connessioni, assenza di presidi antisismici). Tali condizioni possono indurre danni gravi ed estesi crolli anche per terremoti di magnitudo medio-alta (intorno a 6), come confermato dalla storia sismica Italiana negli ultimi 40 anni. Lo scenario, purtroppo, non è migliorato con l’avvento delle normative sismiche (anni ’80), la cui applicazione, sia in termini di tecniche d’intervento che di metodi di verifica, ha comportato ibridizzazioni degli edifici tuttora difficili da interpretare.
Ne consegue che, allo stato attuale, la presenza di interventi e dei loro effetti (sia positivi che negativi) non è più trascurabile. Le osservazioni post-sisma degli ultimi 20 anni (dal sisma Umbria-Marche 1997) hanno registrato l’elevata frequenza di danni gravi e crolli causati da interventi strutturali, soprattutto applicati a solai e coperture (rinforzo e/o sostituzione con sistemi moderni in c.a. o con elementi in acciaio) senza un adeguato consolidamento delle murature. In tal caso, il comportamento ‘scatolare’ è solo presunto, e l’applicazione di modelli di calcolo globali può portare a valutazioni inaffidabili.
A valle di un’estesa revisione degli attuali strumenti schedografici disponibili per il rilievo in sito degli edifici in muratura in zona sismica, l’articolo propone una nuova scheda integrata multi-livello in grado di valutare l’effetto dei più comuni interventi adottati in zona sismica, in termini danno e vulnerabilità. La nuova procedura, calibrata su un esteso campione di edifici (circa 600) appartenenti a 7 centri colpiti dal sisma Italia Centrale 2016, ha permesso di aggiornare le matrici di probabilità di danno (DPM) e le relative distribuzioni in funzione delle intensità della Scala Macrosismica Europea (EMS 98). In particolare, è stato possibile ri-collocare gli edifici con interventi nelle classi di vulnerabilità previste dalla scala (in alcuni casi sono state identificate nuove sotto-classi), in relazione ad intensità macrosismiche variabili tra VI e X
Valutazioni di vulnerabilità sismica di strutture a grandi blocchi. Il caso di Hierapolis di Frigia
No full textA Hierapolis di Frigia sono numerose le strutture indagate al fine della valutazione di sicurezza in rapporto alla creazione di un parco archeo-sismologico dove possano essere fruite in sicurezza le grandi rovine che caratterizzano la zona. Alcuni edifici, come le Terme-chiesa si caratterizzano per essere realizzati in grandi blocchi di travertino, spesso a secco, e mostrano evidenti i segni tanto dei terremoti quanto degli interventi di restauro del passato.
Le indagini e le simulazioni numeriche hanno interessato, oltre alle Terme-chiesa, anche le strutture residue del Martyrion di S. Filippo, alcune tombe monumentali e le imponenti latrine pubbliche della città. Le indagini consistono nel rilievo geometrico completo con l’individuazione dello stato di danno e di degrado e delle fasi costruttive antiche, la caratterizzazione sismica del suolo e la qualificazione dei grandi blocchi che compongono le strutture. Sulle strutture in elevazione sono state realizzate, ove possibile: prove soniche ed endoscopiche supportate da un esteso laser scanner che ha consentito il rilievo esatto della posizione dei blocchi.
Le maggiori vulnerabilità rispetto all’attivazione di meccanismi di primo modo sono state riscontrate nelle latrine, dove sono numerosi i blocchi snelli completamente isolati da altre strutture, e nelle tombe, dove pure la maggior cura degli ammorsamenti murari testimonia una maggiore attenzione al problema sismico.
Nelle terme-chiesa si riscontra la presenza sia di danni evidentemente originati dai sismi storici (strapiombi di murature, deformazioni di archi, scorrimento dei blocchi) sia di interventi di restauro volti ad aumentare la sezione dei contrafforti e a diminuire la luce delle volte allora esistenti. Le strutture sopravvissute sono state analizzate in maniera completa, ricorrendo alla modellazione al continuo (FEM), agli elementi discreti (DEM) e alle condizioni di equilibrio limite, evidenziando la vulnerabilità delle stesse e la suscettibilità ad una evoluzione del danno in rapporto a prevedibili futuri terremoti
- …
