Carozza, Stefano (2017) Performance-based structural reliability assessment for rainfall-induced hydrogeological phenomena. [Tesi di dottorato]


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Item Type: Tesi di dottorato
Resource language: English
Title: Performance-based structural reliability assessment for rainfall-induced hydrogeological phenomena
Date: 29 March 2017
Number of Pages: 144
Institution: Università degli Studi di Napoli Federico II
Department: Strutture per l'Ingegneria e l'Architettura
Scuola di dottorato: Ingegneria civile
Dottorato: Ingegneria strutturale, geotecnica e sismica
Ciclo di dottorato: 29
Coordinatore del Corso di dottorato:
Jalayer, FatemehUNSPECIFIED
Date: 29 March 2017
Number of Pages: 144
Keywords: Risk assessment; structural reliability; limit states; uncertainty propagation; hazard; hydrogeological phenomena; debris flow; flood; vulnerability; fragility; safety checking; decision support system; software implementation.
Settori scientifico-disciplinari del MIUR: Area 08 - Ingegneria civile e Architettura > ICAR/09 - Tecnica delle costruzioni
Area 09 - Ingegneria industriale e dell'informazione > ING-INF/05 - Sistemi di elaborazione delle informazioni
Area 01 - Scienze matematiche e informatiche > MAT/06 - Probabilità e statistica matematica
Date Deposited: 23 Apr 2017 19:48
Last Modified: 13 Mar 2018 07:50
DOI: 10.6093/UNINA/FEDOA/11462

Collection description

Risk assessment for rainfall-induced hydrogeological phenomena in urban areas is an important issue for stakeholders, in order to manage the hydrogeological risk in urbanized areas and to plan the future urbanization. The aim of this work is to propose a complete framework for risk assessment in urban areas for two main rainfall-induced phenomena: debris flow and flooding. The work involves several disciplines and wraps them together in a systematic way in order to be used as a DSS (Decision Support System). The work presented in this thesis is developed within the Italian research project METROPOLIS funded by the National Operative Program (PON 03PE_00093_4) and focused on the study of the integrated and sustainable methods and technologies for resilience and safety of urban systems. The project aims at defining the methodology and at developing innovative and sustainable technologies for the evaluation and management of the natural and anthropic risks for urban systems, in order to address mitigation strategies based on integrated decision support systems. The thesis focuses on the reliability assessment of portfolios of buildings located in areas susceptible to hydrogeological hazards. A portfolio of buildings can include one or more structural classes where a given class is characterized by a group of features (e.g., building material, decade of construction, number of storeys, etc.). Within each class, specific statistical considerations are made to characterize both the uncertainty due to lack of knowledge and building-to-building variability in mechanical, geometrical and load properties. The adopted framework is draws obvious analogies with the Performance Based Earthquake Engineering (PBEE) framework. In the context of risk assessment, three main aspects are investigated: the hazard, the vulnerability and the exposure. The first two aspects are described in detail; the exposure quantification, instead, is outside the scope of this work. The hazard evaluation involves specific geological, geotechnical, hydrological and hydraulic competences. This issue has been addressed by a team of specialists that produced the hazard maps for this work for both debris flows and flooding. While for flooding problem it is possible to obtain a complete hazard curve (for each geographical point of interest) in terms of intensity measure (e.g., flood height and/or flood velocity) versus return period of the rainfall event, for debris flow phenomena the question is much more complex. In case of debris flow, in fact, the event does not depend only on return period of the rainfall that triggers the debris flow but depends also on the boundary and initial conditions of the slope. The knowledge of these conditions is almost never available in un-gauged conditions; hence, a scenario-based approach has been adopted in order to solve the risk assessment problem. Analytic vulnerability assessment is performed by calculating the robust fragility curves representing the probability to have an intensity measure value lower than or equal to a certain value which correspond to assumed limit states –considering also the uncertainties in the parameters of the fragility model. The fragility curves represent the vulnerability of a structural class and are calculated by adopting a Bayesian approach and relying on a Monte Carlo Simulation (MCS) process for the propagation of uncertainties. In order to estimate the structural capacity for a given limit state, an incremental analysis procedure has been performed during the MCS. The structural model is elastic and finite-element-based accompanied by a defined set of safety checks in order to catch all the potential failure mechanisms of the walls –arguably the most vulnerable structural elements directly subjected to hydrogeological-induced actions. In this thesis, the proposed framework is implemented in an Object-Oriented Java software tool, named HydRA. HydRA performs the propagation of uncertainties in a MCS process by executing a specified number of structural analyses of models generated according to user-defined probability distributions (through the MCS process). HydRA produces as results: the safety checks, the robust fragility curves for specified limit states and the risk maps. The framework is applied on three case studies. In order to validate the structural model and the analysis procedure, two past events have been considered: the flash flood/debris flow event in Scaletta Zanclea (Messina, Italy) occurred in 2009 (a single masonry building has been considered) and the debris flow in Sarno (Salerno, Italy) occurred in 1998 where a portfolio of buildings has been considered. Finally, an application on Castellammare di Stabia (Naples, Italy) is proposed in order to provide the risk maps as an instrument in the service of risk management and promoting risk awareness for hydrogeological phenomena.


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