This paper intends to deepen a particularly challenging and important topic, the design procedures of structural steel storage racks. Experimental and analytical studies of the performance of storage racks are scarce and, consequently, they have not significantly influenced the development of codes related to rack systems. Therefore, this type of structures are dimensioned according to inadequate regulations, both in the static and seismic field, as they do not take into account the behaviour peculiarities related to the presence of structures composed of elements having only one axis of symmetry. Numerous studies have been conducted in the static field, while there are very few seismic researches aimed to improve the design rules that are currently available for these systems, which, however, have to be functional even in seismic areas. The safety limitations rely mostly on the lack of knowledge of the actions to be applied to the structures and on the unawareness of the importance of the structural behaviour in terms of ductility. Particularly, after an introductory part (Chapter 1) related to the presentation of the objective of the thesis, one passes to the main problems associated to the instability issue (Chapter 2), a globally present phenomenon for this type of structures. Afterwards, the Finite Element formulation is explained (Chapter 3), being a necessary approach for the structural analysis and design of these framed systems. Thereafter, one presents an overview regarding the design rules that are to be used both in the static and seismic field, and therefore it becomes necessary to present a parametric analysis (Chapter 4), varying the number of spans (beams), the number of loading levels and the applied load. The static performance is evaluated (Chapter 5) and only after, there is appraised the seismic design, valuing the structures’ behaviour factor (Chapter 6), using Fajfar’s Approach, an incorporated procedure in the Eurocode 8, which accurately allows the use of the pushover analyses for the assessment of the seismic response. Then, as a result of these study, there are applied three different methods in order to evaluate the seismic performance characteristics (Chapter 7), comparable to the previously obtained static capacity. The results undoubtedly suggest the need for the development of clear and unambiguous norms and regulations, as missing details in the legislation may generate substantial differences between values of the seismic performance for the same structure, depending on the choice of designers. To put it briefly, the present thesis aims to enrich the state of knowledge of the dimensioning process of the structural steel storage racks and treats different methodologies for the seismic design procedures. In particular, subsequent to a parametric analysis of the framed storage structures, the seismic performance is evaluated also in terms of static performance.
Questo lavoro di tesi intende approfondire un argomento particolarmente impegnativo e importante - le procedure di progettazione delle scaffalature metalliche. Studi sperimentali e analitici della prestazione delle scaffalature sono scarse e, di conseguenza, non hanno influenzato significativamente lo sviluppo dei codici relativi. Pertanto, questo tipo di strutture sono dimensionati secondo norme inadeguate, sia in campo statico e sismico, in quanto non tengono conto delle peculiarità di comportamento legati alla presenza di strutture composte di elementi aventi un solo asse di simmetria. Sono stati condotti numerosi studi nel campo statico, mentre ci sono poche ricerche sismiche volte a migliorare le regole di progettazione che sono attualmente disponibili per questi sistemi, che, tuttavia, devono essere funzionali anche in zone sismiche. Le limitazioni di sicurezza si basano principalmente sulla mancanza di conoscenza delle azioni da applicare alle strutture e sulla inconsapevolezza dell'importanza del comportamento strutturale in termini di duttilità. In particolare, dopo una parte introduttiva (Capitolo 1) relativa alla presentazione dell'obiettivo della tesi, si passa ai principali problemi associati al problema dell'instabilità (Capitolo 2), un fenomeno presente globalmente per questo tipo di strutture. In seguito, la formulazione degli elementi finiti viene spiegata (capitolo 3), essendo un approccio necessario per l'analisi strutturale e progettazione di questi sistemi intelaiati. Successivamente, viene presentata una panoramica riguardante le regole di progettazione che devono essere utilizzate sia in campo statico e sismico, e quindi diventa necessario introdurre un'analisi parametrica (capitolo 4), variando il numero di campate (travi), il numero di livelli di carico e il carico applicato. La capacità statica viene valutata (capitolo 5) e solo dopo, si è valutata la capacità sismica, valorizzando il fattore di struttura (capitolo 6) mediantecon l’approccio di Fajfar, una procedura incorporata nell'Eurocodice 8, che consente accuratamente l'uso dell’analisi di pushover per la valutazione della risposta sismica. Poi, come risultato di questi studi, sono stati applicati tre metodi diversi per valutare la capacità sismica (Capitolo 7), paragonabile alla capacità statica precedentemente ottenuta. I risultati suggeriscono indubbiamente la necessità di sviluppare norme e regolamenti chiari ed univoci, visto che i dati mancanti nella normativa possono generare differenze sostanziali tra i valori della prestazione sismica per la stessa struttura, a seconda delle scelte fatte dal produttore. Per dirla in breve, la presente tesi si propone di arricchire lo stato delle conoscenze del dimensionamento delle scaffalature metalliche e tratta metodologie diverse per ottenere la risposta sismica. In particolare, in seguito ad una analisi parametrica delle strutture intelaiate di stoccaggio, la prestazione sismica è valutata anche in termini di prestazione statica.
Seismic performance of industrial storage pallet racks
TOMESCU, SABINA
2014/2015
Abstract
This paper intends to deepen a particularly challenging and important topic, the design procedures of structural steel storage racks. Experimental and analytical studies of the performance of storage racks are scarce and, consequently, they have not significantly influenced the development of codes related to rack systems. Therefore, this type of structures are dimensioned according to inadequate regulations, both in the static and seismic field, as they do not take into account the behaviour peculiarities related to the presence of structures composed of elements having only one axis of symmetry. Numerous studies have been conducted in the static field, while there are very few seismic researches aimed to improve the design rules that are currently available for these systems, which, however, have to be functional even in seismic areas. The safety limitations rely mostly on the lack of knowledge of the actions to be applied to the structures and on the unawareness of the importance of the structural behaviour in terms of ductility. Particularly, after an introductory part (Chapter 1) related to the presentation of the objective of the thesis, one passes to the main problems associated to the instability issue (Chapter 2), a globally present phenomenon for this type of structures. Afterwards, the Finite Element formulation is explained (Chapter 3), being a necessary approach for the structural analysis and design of these framed systems. Thereafter, one presents an overview regarding the design rules that are to be used both in the static and seismic field, and therefore it becomes necessary to present a parametric analysis (Chapter 4), varying the number of spans (beams), the number of loading levels and the applied load. The static performance is evaluated (Chapter 5) and only after, there is appraised the seismic design, valuing the structures’ behaviour factor (Chapter 6), using Fajfar’s Approach, an incorporated procedure in the Eurocode 8, which accurately allows the use of the pushover analyses for the assessment of the seismic response. Then, as a result of these study, there are applied three different methods in order to evaluate the seismic performance characteristics (Chapter 7), comparable to the previously obtained static capacity. The results undoubtedly suggest the need for the development of clear and unambiguous norms and regulations, as missing details in the legislation may generate substantial differences between values of the seismic performance for the same structure, depending on the choice of designers. To put it briefly, the present thesis aims to enrich the state of knowledge of the dimensioning process of the structural steel storage racks and treats different methodologies for the seismic design procedures. In particular, subsequent to a parametric analysis of the framed storage structures, the seismic performance is evaluated also in terms of static performance.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/114122