1,721,006 research outputs found
Exploring probabilistic seismic risk assessment accounting for seismicity clustering and damage accumulation: Part I. Hazard analysis
No full textProbabilistic seismic hazard analysis (PSHA), as a tool to assess the probability that ground motion of a given intensity or larger is experienced at a given site and time span, has historically comprised the basis of both building design codes in earthquake-prone regions and seismic risk models. The PSHA traditionally refers solely to mainshock events and typically employs a homogeneous Poisson process to model their occurrence. Nevertheless, recent disasters, such as the 2010–2011 Christchurch sequence or the 2016 Central Italy earthquakes, to name a few, have highlighted the potential pitfalls of neglecting the occurrence of foreshocks, aftershocks, and other triggered events, and pinpointed the need to revisit the current practice. Herein, we employ the epidemic-type aftershock sequence (ETAS) model to describe seismicity in Central Italy, investigate the model’s capability to reproduce salient features of observed seismicity, and compare ETAS-derived one-year hazard estimates with ones obtained with a standard mainshock-only Poisson-based hazard model. A companion paper uses the hazard models derived herein to compare and contrast loss estimates for the residential exposure of Umbria in Central Italy
RINTC-E project: Towards the assessment of the seismic risk of existing buildings in Italy
No full textThe 2019-2021 RINTC project is the extension of the 2015-2017 RINTC project that assessed, explicitly, the seismic risk of code-conforming Italian structures (i.e., designed according to the seismic code currently enforced). The aim of the new RINTC project is to extend the methodological framework developed in RINTC to the existing structures (designed and built before 2008), which constitute the vast majority of Italian building stock. In 2018 some analyses, preliminary with respect to the 2019-2021 project, were carried out; i.e., the 2018 RINCT-e project. In particular, five structural typologies were considered: masonry, reinforced concrete, pre-cast reinforced concrete, steel, and seismically isolated buildings. In the framework of the 2018 project, several archetype structures for each typology have been designed and/or retrofitted according to standard practices consistent with outdated codes, enforced since the eighties, for five sites across Italy spanning a wide range of seismic hazard levels (evaluated according to current standards). The seismic vulnerability of the designed structures was assessed by subjecting three-dimensional nonlinear computer models to multi-stripe non-linear dynamic analysis. Integration of the probabilistic hazard and probabilistic vulnerability (i.e., fragility) yields the annual failure rate for each of the designed and modeled structure. In the paper, the 2019-2021 RINTC project is introduced and the preliminary failure rates of the existing structures are presented
RINTC project: assessing the (implicit) seimsic risk of code-conforming structures in Italy
No full textRINTC, which started in 2015, is a joint proj
ect of ReLUIS and EUCENTRE, two
centers of competence
for seismic risk assessment
of the Italian civil protection. The goal of the
project
, which is still ongoing,
is
to assess in an explicit manner the
seismic
risk of structures
designed according
to
the code currently enforced in Italy. To this aim five structural typologies
were considered: masonry, reinforced concrete, pre
-
cast reinforced concrete, steel, and
seismically isolated buildin
gs. In the framework of the project, multiple archetype
structures
have been designed for each typology according to standard practice at five sites across Italy,
spanning a wide range of
seismic
hazard levels. The seismic vulnerability of the designed
st
ructures was assessed by subjecting 3D computer models to
multi
-
stripe non
-
linear dynamic
analysis. Integration of the probabilistic hazard and
probabilistic
vulnerability
(i.e., fragility)
yielded
the
annual failure rate, in terms of
onset of non
-
structural
damage and collapse, of each
of the structures. Risk assessment takes into consideration record
-
to
-
record variability of non
-
structural response and, for selected cases, structural modeling uncertainty. Results
preliminarily
show that, for each structural
typology,
the
collapse
risk tend
s
to increase
with
the hazard of the site and that risk is not uniform a
cross
typologies
Effects of masonry walls on the seismic risk of reinforced concrete frame buildings
No full textThe observation of building damage after earthquakes has shown that the contribution to the seismic performance of concrete frame buildings from infill walls is significant and should not be ignored. Despite the added mass and the shortening of the structure's fundamental vibration period that may cause a boost in earthquake-induced inertia forces, the presence of infill walls is often beneficial due to the additional strength and energy-dissipation capacity that they provide. In this study we considered 4-, 6-, 8- and 12-story concrete frame buildings with regular plan and stiffness and mass distributions along the height. For each height we modeled three different frame/wall configurations: bare frame; frame with masonry infills at all stories; and frame with infills at all but ground level. We considered bare frames because it is the scheme routinely used for design, in which masonry walls are deemed non-structural and their contributions neglected. To represent buildings with several combinations of lateral strength and structure ductility requirements, we designed bare frames for different base shear values. We located this suite of buildings with and without infill walls in four Italian cities with different earthquake hazard and compared the probabilistic losses. Copyright © (2006) by Earthquake Engineering Research Institute
Lezioni dal terremoto dell’Abruzzo: il comportamento degli edifici visto dall’angolo prospettico della regola d’arte nel costruire
No full textInfluenza delle tamponature sul rischio sismico degli edifici in calcestruzzo armato
No full textL’osservazione dei danni causati da terremoti in occasione di eventi sismici recenti indica che la presenza di tamponature influisce in maniera significativa sul comportamento degli edifici a telaio in calcestruzzo armato.
Pertanto, benché i pannelli murari di tamponatura siano generalmente ritenuti elementi non strutturali, e che di conseguenza si tenda a non considerare in maniera esplicita il loro contributo alla risposta sismica, in numerosi casi appare non lecito trascurare tale contributo. In effetti, nonostante il fatto che la presenza delle tamponature risulti spesso benefica a causa dell’incremento della resistenza e della capacità di dissipare energia, l’aumento della massa e la riduzione del periodo fondamentale di vibrazione della strutture costituiscono
fattori che tendono a incrementare le ordinate spettrali rispetto al caso dello stesso telaio considerato privo di tamponature. Nel presente lavoro sono stati esaminati telai in c.a. di 4, 6, 8 e 12 piani, regolari in quanto a distribuzione di massa e rigidezza lungo l’altezza. Per ogni tipologia di altezza sono state studiate 2 configurazioni di tamponatura: telaio nudo e telaio interamente tamponato. Lo studio del telaio nudo è giustificato dal
fatto che questo, appunto, rappresenti il modello di calcolo usualmente adottato in fase di progetto. Al fine di descrivere il comportamento di edifici con diverse combinazioni di resistenza alle forze orizzontali e richiesta di duttilità di progetto, sono stati progettati telai non tamponati con differenti valori di taglio resistente alla base. Si è ipotizzato di collocare i telai così progettati in alcune città italiane, differenti per grado di sismicità
e stile sismico, in modo da poter effettuare una serie di confronti tra le perdite attese, calcolate con un approccio interamente probabilistico, in relazione ai diversi schemi strutturali
Influenza della modellazione strutturale sulla risposta sismica di telai in cemento armato tamponati
No full textFloor Response Spectra for Bare and Infilled Reinforced Concrete Frames
No full textThe objective of this article is to study the effects of structural nonlinear behavior on Floor Response Spectra (FRS) of existing reinforced concrete frames. This study examines how the FRS vary with the level of post-elastic behavior in buildings of different number of stories and masonry infill wall configurations. The effect of damping modeling assumptions is also investigated. Differences and similarities with findings from the literature are discussed. On the basis of the obtained results, a commentary on the adequacy of basic assumptions used in predictive equations proposed by different seismic codes is offered
Floor acceleration demand in reinforced concrete frame structures with masonry infill walls
No full textThis study deals with the assessment of floor acceleration demands on reinforced concrete moment-resisting frames (RCFs) representative of typical building inventory in Italy. Floor acceleration can be used to estimate damage to nonstructural components. To this purpose we have considered 2-, 4-, 6- and 10-story concrete frame buildings with regular plan and stiffness and mass distributions along the height and designed for different base shear values. For each height we modeled three different frame/wall configurations: bare frame, frame with masonry infill walls at all stories, and frame with infill walls at all stories but ground level. In this article we have examined under what
circumstances the presence of infill walls influences the peak and spectral floor acceleration demands along the height of these concrete frame buildings
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