Nowadays, the demand for industrial buildings accommodating long spans, typical of exhibition halls or hangars, is increasing, mainly due to the evolution of the logistic sector. Whilst uncommon spans for such buildings were traditionally dealt with steel trusses, precast concrete solutions have been proposed since the ‘70s to cover this need, with current span limitations of up to 50 m for beams and 42 m for roof elements. The main objective of this thesis is to investigate the structural behaviour of an unconventional prefabricated reinforced concrete system by analysing a case study building layout with beams spanning up to 72 m supported by cable stays. This system is an evolution of a patented precast construction system, named Ondal. A full design process according to Eurocodes was carried out considering both static and seismic load combinations, with increasing levels of earthquake hazard. Four buildings were designed: one according to static loads only, the other three according to ground acceleration levels associated to low (0.1g), medium (0.2g) and high (0.3g) seismic hazard. The horizontal beam and roof elements, not explicitly part of the lateral load resisting system, have been designed for gravity loading. A parametric study was conducted for the edge column and for the central column/cable-stayed modulus, modifying their side dimensions in order to achieve balanced transnational vibration periods along both main axes. Numerical simulations were subsequently carried out with increasing complexity. At first, linear dynamic analysis with response spectrum was employed to obtain the dimensions of the column/antenna elements, assuming a rigid diaphragm behaviour and decoupled cladding panel system. The rigid diaphragm assumption was removed later on, after introducing in the model all horizontal slab elements and their dowel connections, which allowed to set their proportioning. The joint connections between the main beam and the edge/peripheral columns were also simulated. Critical factors for the design of the lateral load resisting system were found to be the flexibility limitation factor theta for low hazard PGAs and the flexural strength for medium and high hazard PGAs. With the aim to check the real structural performance of the overall assembly under seismic accelerogram, the building with explicit diaphragm modelling designed for medium (PGA = 0.2g) seismic hazard was subjected to a series of non-linear dynamic time history analyses, considering a single accelerogram with PGA progressively scaled to 0.1g, 0.2g, 0.3g, 0.4g, and 0.5g. These analyses highlighted the proper design procedure adopted, with limited drift and no plasticisation observed in any structural element around the damage limit state, while only limited damage was noticed at the design PGA around the life safety limit state. Another important remark was the large seismic overstrength of the considered structural system, which attained incipient failure for bow effect of the antenna induced by second order moments in the direction transverse to the cables only for PGA as strong as 0.4g. Moreover, in the direction longitudinal to the cables failure was not attained even for PGA as strong as 0.5g.
Oggigiorno, la richiesta di edifici industriali di grande luce, tipicamente fiere o grandi rimesse/depositi, è in crescita, principalmente a causa dell’evoluzione del settore della logistica. Mentre edifice di questo genere sono stati tradizionalmente realizzati con strutture reticolari metalliche nel passato, dagli anni ’70 si sono succedute soluzioni ardite nel campo della prefabbricazione in calcestruzzo armato, con gli attuali limiti di luce posti a circa 50 m per le travi e a 42 m per i tegoli. L’obiettivo principale di questo elaborato è studiare il comportamento strutturale di un sistema di prefabbricazione industriale non convenzionale attraverso un caso studio di un edificio con travi di luce fino a 72 m sostenute da stralli metallici. Questo sistema è un’evoluzione della serie brevettata Ondal. Un processo completo di progettazione è stato eseguito in accordo con l’approccio degli Eurocodici considerando sia carichi statici sia sismici con crescenti livelli di pericolosità. Quattro edifici sono stati progettati: uno in accord ai soli carichi statici, gli altri tre in base ad accelerazioni di picco del terreno (PGA) associabili a pericolosità bassa (0.1g), media (0.2g) e alta (0.3g). Gli elementi orizzontali di trave e tegolo, non facenti esplicitamente parte del sistema resistente alle azioni orizzontali, sono stati progettati per carichi gravitazionali. Uno studio parametrico ha permesso di identificare le dimensioni sezionali idonee del pilastro laterale e del modulo centrale strallato per ottenere periodi associati a moto traslazionali simili in ambedue le direzioni principali. Sono state condotte analisi numeriche di crescente complessità. Inizialmente, le dimensioni degli elementi di pilastro/antenna sono stati dimensionati in accordo con l’analisi dinamica lineare con spettro di risposta considerando un effetto di diaframma rigido e un efficace disaccoppiamento del moto dei pannelli di tamponamento da quello della struttura. Successivamente, l’ipotesi di diaframma rigido è stata rimossa con la modellazione esplicita dei tegoli e di tutte le connessioni spinottate di piano. Fattori critici per la progettazione della struttura sono risultati essere il fattore di limitazione di flessibilità teta per bassa pericolosità sismica, e la resistenza flessionale per pericolosità media e alta. Con l’obiettivo di controllare la reale prestazione strutturale dell’intera struttura sotto accelerogramma sismico, l’edificio progettato per zona a pericolosità media (PGA = 0.2g) con diaframma esplicito è stato sottoposto a una serie di analisi dinamiche non lineari considerando un singolo accelerogramma scalato progressivamente a PGA di 0.1g, 0.2g, 0.3g, 0.4g, e 0.5g. Tali analisi hanno sottolineato un buon inquadramento progettuale fornito dall’approccio progettuale adottato, con limitati spostamenti e assenza di plasticizzazione alla base dei pilastri/antenne per un sisma riconducibile allo stato limite di danno, e un limitato danneggiamento per un sisma riconducibile allo stato limite di salvaguardia della vita. Un’altra importante osservazione è relativa alla notevole sovraresistenza del sistema strutturale considerato, che ha raggiunto incipiente collasso nella direzione ortogonale ai cavi per effetto arco dell’antenna indotto da momenti del secondo ordine solamente con accelerogramma scalato con PGA di 0.4g. Inoltre, nella direzione parallela ai cavi non è stato raggiunto il collasso nemmeno con accelerogramma scalato con PGA di 0.5g.
Structural behaviour of a long-span cable-stayed precast industrial building under static and seismic actions
Vlachaki Karagiannopoulou, Sofia
2019/2020
Abstract
Nowadays, the demand for industrial buildings accommodating long spans, typical of exhibition halls or hangars, is increasing, mainly due to the evolution of the logistic sector. Whilst uncommon spans for such buildings were traditionally dealt with steel trusses, precast concrete solutions have been proposed since the ‘70s to cover this need, with current span limitations of up to 50 m for beams and 42 m for roof elements. The main objective of this thesis is to investigate the structural behaviour of an unconventional prefabricated reinforced concrete system by analysing a case study building layout with beams spanning up to 72 m supported by cable stays. This system is an evolution of a patented precast construction system, named Ondal. A full design process according to Eurocodes was carried out considering both static and seismic load combinations, with increasing levels of earthquake hazard. Four buildings were designed: one according to static loads only, the other three according to ground acceleration levels associated to low (0.1g), medium (0.2g) and high (0.3g) seismic hazard. The horizontal beam and roof elements, not explicitly part of the lateral load resisting system, have been designed for gravity loading. A parametric study was conducted for the edge column and for the central column/cable-stayed modulus, modifying their side dimensions in order to achieve balanced transnational vibration periods along both main axes. Numerical simulations were subsequently carried out with increasing complexity. At first, linear dynamic analysis with response spectrum was employed to obtain the dimensions of the column/antenna elements, assuming a rigid diaphragm behaviour and decoupled cladding panel system. The rigid diaphragm assumption was removed later on, after introducing in the model all horizontal slab elements and their dowel connections, which allowed to set their proportioning. The joint connections between the main beam and the edge/peripheral columns were also simulated. Critical factors for the design of the lateral load resisting system were found to be the flexibility limitation factor theta for low hazard PGAs and the flexural strength for medium and high hazard PGAs. With the aim to check the real structural performance of the overall assembly under seismic accelerogram, the building with explicit diaphragm modelling designed for medium (PGA = 0.2g) seismic hazard was subjected to a series of non-linear dynamic time history analyses, considering a single accelerogram with PGA progressively scaled to 0.1g, 0.2g, 0.3g, 0.4g, and 0.5g. These analyses highlighted the proper design procedure adopted, with limited drift and no plasticisation observed in any structural element around the damage limit state, while only limited damage was noticed at the design PGA around the life safety limit state. Another important remark was the large seismic overstrength of the considered structural system, which attained incipient failure for bow effect of the antenna induced by second order moments in the direction transverse to the cables only for PGA as strong as 0.4g. Moreover, in the direction longitudinal to the cables failure was not attained even for PGA as strong as 0.5g.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/173369