In conventional design approaches, structural safety is assessed without considering extreme load conditions that may cause global system collapse as a consequence of local failures in a component. A few studies have been carried out so far, emphasizing the need for probabilistic risk assessment and management of structures to disproportionate (or progressive) collapse. To this aim, fragility analysis may be used to predict the probability of progressive collapse, as a function of a intensity measure, given that local damage has occurred. In this research, fragility functions for low-rise reinforced concrete (RC) framed building structures are presented to be implemented in progressive collapse risk assessment. Two building classes representative of European buildings designed for gravity loads and earthquake resistance in accordance with Eurocodes 2 and 8, respectively, were investigated. Fiber-based finite element (FE) models were developed and integrated with numerical techniques able to simulate the removal of first-story columns within an open source platform. Based on statistics and probability distribution functions for geometry, material properties and loads of the case-study building classes, Monte Carlo simulation was performed to generate random realizations of structural models. Fragility functions at multiple damage states show a significant influence of both seismic design/detailing and secondary beams on robustness of the case-study RC building classes. Analysis non-linear dynamic and static were performed. Furthermore, the same analyzes were carried out by subjecting the structure to loads regulated by legislation UFC (Unified Facilities Criteria).
Modelli di fragilità: un caso studio per il collasso progressivo di strutture a telaio in C.A. progettate a carichi gravitazionali e sismici . Negli approcci progettuali convenzionali, viene valutata la sicurezza strutturale senza considerare le condizioni di carico estreme che possono causare il collasso del sistema globale come conseguenza di guasti locali in una componente. Alcuni studi sono stati condotti finora, sottolineando la necessità di una valutazione probabilistica del rischio e della gestione di strutture per collasso progressivo. A questo scopo, l'analisi di fragilità può essere usata per predire la probabilità di collasso progressivo, a seguito del verificarsi di un danno locale. In questa ricerca, sono presentati modelli di fragilità per un edificio in Cemento Armato intelaiato per la valutazione del rischio di crollo. Sono stati studiati due diversi classi di edifici progettati per soli carichi verticali e per resistere a carichi sismici secondo Eurocodice 2 e 8, rispettivamente. Modelli ad elementi finiti in fibra sono stati sviluppati e integrati con tecniche numeriche in grado di simulare la rimozione di colonne al primo piano dell’edificio. Sulla base delle statistiche e funzioni di distribuzione di probabilità per la geometria, le proprietà dei materiali e carichi delle diverse classi di costruzioni, è stata eseguita una simulazione Monte Carlo per generare realizzazioni casuali di modelli strutturali. Sono state eseguite analisi non lineari sia dinamiche che statiche. Inoltre, le stesse analisi sono state effettuate sottoponendo la struttura a carichi regolati dalla normativa UFC (Unified Strutture Criteria).
Fragility models: a case-study on progressive collapse of R.C. framed structures designed under gravity and seismic loads.
CASTIGLIA, LUCAS FABIAN
2014/2015
Abstract
In conventional design approaches, structural safety is assessed without considering extreme load conditions that may cause global system collapse as a consequence of local failures in a component. A few studies have been carried out so far, emphasizing the need for probabilistic risk assessment and management of structures to disproportionate (or progressive) collapse. To this aim, fragility analysis may be used to predict the probability of progressive collapse, as a function of a intensity measure, given that local damage has occurred. In this research, fragility functions for low-rise reinforced concrete (RC) framed building structures are presented to be implemented in progressive collapse risk assessment. Two building classes representative of European buildings designed for gravity loads and earthquake resistance in accordance with Eurocodes 2 and 8, respectively, were investigated. Fiber-based finite element (FE) models were developed and integrated with numerical techniques able to simulate the removal of first-story columns within an open source platform. Based on statistics and probability distribution functions for geometry, material properties and loads of the case-study building classes, Monte Carlo simulation was performed to generate random realizations of structural models. Fragility functions at multiple damage states show a significant influence of both seismic design/detailing and secondary beams on robustness of the case-study RC building classes. Analysis non-linear dynamic and static were performed. Furthermore, the same analyzes were carried out by subjecting the structure to loads regulated by legislation UFC (Unified Facilities Criteria).È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
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https://hdl.handle.net/20.500.14239/19794