Precast buildings represent a large portion of the built heritage and the new constructions adopted for industrial long-span structures in seismic areas in Italy. Design and detailing of these structural systems generally lead to a dynamic behavior characterized by significant flexibility and displacement capacity. Recent major earthquake events highlighted that the seismic response of this structural typology under medium to large ground motions can be largely influenced by the mechanical interaction between load-bearing precast frame, cladding panels and roof system. This thesis aims to evaluate the seismic risk considering the site of Milan in Italy and to study in detail a long span industrial building. The probabilistic-based structural response has been assessed based on the results of static nonlinear analysis and multi-stripe dynamic nonlinear analyses carried out with the OpenSees computational code on numerical models. In particular, two numerical models are implemented and analyzed with different levels of geometrical and mechanical complexity. The roof system in the first model relies on the assumption of rigid diaphragm with lumped mass and lumped plasticity and the base of each column, whilst the second model accounts for a more sophisticated offset-based connectivity between each vertical and horizontal frame element as well as the nonlinear mechanical response of dowel connections. For each structural system, ten hazard levels characterized by mean return period ranging from 10 up to 100000 years have been considered. Demand over capacity curves conditional on a prescribed seismic intensity measure representative of the hazard level allow for a quantitative evaluation of the seismic vulnerability of the structural system considering record-to-record variability and a direct comparison of the influence of the rigid diaphragm. Based on the demand over capacity curves, it is possible to carry out reliability assessment of each structural system has been carried out for both damage and collapse limit states. The work included in the thesis has been developed as part of the national research project RINTC (Implicit Risk of Italian Code Conforming Structures) commissioned to ReLUIS (Rete dei Laboratori Universitari di Ingegneria Sismica). The project is funded by the Italian Civil Protection Department and aims at assessing the implicit risk of code-conforming structures.
Gli edifici prefabbricati di grande luce rappresentano gran parte del patrimonio edilizio italiano e delle nuove costruzioni adottate per le strutture industriali in zona sismica. I recenti eventi sismici hanno evidenziato come la risposta dinamica di questa tipologia strutturale possa essere particolarmente influenzata dall’interazione meccanica tra telaio portante, pannelli di rivestimento perimetrale e sistema di copertura. Il presente elaborato di tesi ha come obiettivo la valutazione del rischio sismico associato di un edificio industriale di grande luce soggetto ad livello di pericolosità sismica lieve, associato al sito di Milano. La risposta strutturale probabilistica è stata valutata mediante analisi statica non lineare e analisi dinamiche multi-striscia non lineari attraverso modelli numerici a plasticità concentrata sviluppati con il codice di calcolo OpenSees. In particolare, sono stati sviluppati ed implementati due modelli numerici caratterizzati da un diverso grado di complessità geometrica e di modellazione del comportamento meccanico. Il sistema di copertura del primo modello si basa sull’ipotesi di diaframma rigido con massa concentrata e di plasticità concentrata alla base degli elementi verticali. Il secondo modello presenta una sofisticata connettività basata su offset rigidi tra gli elementi orizzontali del sistema di coperta e introduce legami costitutivi non lineari per simulare il comportamento meccanico delle connessioni spinottate. Per ogni sistema strutturale, vengono considerati dieci livelli di pericolosità sismica associati ad un tempo di ritorno medio tra i 10 e 100000 anni. I diagrammi domanda/capacità per una determinata misura di intensità sismica rappresentativa del livello di pericolosità consentono una valutazione quantitativa della vulnerabilità sismica dell’edificio considerando la variabilità dell’input sismico ed un confronto diretto dell’influenza del diaframma rigido. Sulla base dei diagrammi domanda/capacità, è possibile sviluppare analisi di affidabilità sismica rispetto a stati limiti di limitazione del danno e di collasso. Il lavoro di tesi è stato sviluppato nell’ambito del progetto di ricerca di carattere nazionale RINTC (Rischio Implicito delle Norme Tecniche per le Costruzioni NTC italiane) sviluppato da ReLUIS (Rete dei Laboratori Universitari di Ingegneria Sismica). Il progetto è finanziato dal Dipartimento della Protezione Civile e si propone di valutazione il rischio implicito di strutture progettate in conformità alle normative strutturali ed antisismiche vigenti.
Seismic risk assessment of long span precast industrial buildings
TRONCI, SERGIO
2019/2020
Abstract
Precast buildings represent a large portion of the built heritage and the new constructions adopted for industrial long-span structures in seismic areas in Italy. Design and detailing of these structural systems generally lead to a dynamic behavior characterized by significant flexibility and displacement capacity. Recent major earthquake events highlighted that the seismic response of this structural typology under medium to large ground motions can be largely influenced by the mechanical interaction between load-bearing precast frame, cladding panels and roof system. This thesis aims to evaluate the seismic risk considering the site of Milan in Italy and to study in detail a long span industrial building. The probabilistic-based structural response has been assessed based on the results of static nonlinear analysis and multi-stripe dynamic nonlinear analyses carried out with the OpenSees computational code on numerical models. In particular, two numerical models are implemented and analyzed with different levels of geometrical and mechanical complexity. The roof system in the first model relies on the assumption of rigid diaphragm with lumped mass and lumped plasticity and the base of each column, whilst the second model accounts for a more sophisticated offset-based connectivity between each vertical and horizontal frame element as well as the nonlinear mechanical response of dowel connections. For each structural system, ten hazard levels characterized by mean return period ranging from 10 up to 100000 years have been considered. Demand over capacity curves conditional on a prescribed seismic intensity measure representative of the hazard level allow for a quantitative evaluation of the seismic vulnerability of the structural system considering record-to-record variability and a direct comparison of the influence of the rigid diaphragm. Based on the demand over capacity curves, it is possible to carry out reliability assessment of each structural system has been carried out for both damage and collapse limit states. The work included in the thesis has been developed as part of the national research project RINTC (Implicit Risk of Italian Code Conforming Structures) commissioned to ReLUIS (Rete dei Laboratori Universitari di Ingegneria Sismica). The project is funded by the Italian Civil Protection Department and aims at assessing the implicit risk of code-conforming structures.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/169630