Among the numerous issues connected to the construction of a tall building, it is of fundamental importance to take account of some elements, such as the choice of structural typology, the definition of the soliciting actions and the control on the execution phase. As regards the choice of structural typology, three different alternatives are possible: 1. Reinforced concrete core and steel columns 2. Reinforced concrete core and mixed steel-concrete columns 3. Both core and columns in reinforced concrete The choice of structural typology has repercussions for the required control operations of geometry and plan dimensions, applied at run time. This is all due to the fact that concrete has viscoelastic features, while steel it’s only elastic. Furthermore, the contribution rate of concrete either in the core or in the columns, is different. The structural unions, therefore, must allow the associated differential upright displacements. These devices are proposed in order to prevent misalignment, which is also damaging to both static and dynamic performance of the whole structure. A proper approach to this problem requires, first of all, an inclusion of the concept of sequence of construction. Tall buildings are erected by undergoing well defined time sequences; a structural analysis which ignores this aspect can lead to an incorrect evaluation during the design phase. This analyse has developed during a study on the structural behaviour of UniCredit Tower in Milan, comparing, in the first place, all the actions which affect four columns. This project was conducted with regard to three kind of models: one settled in a conventional manner, another in stages, and the last one in stages with effects on creep and shrinkage. Eventually, the examination was extended to the global structure, also evaluating phases extending up to 25 years after the end of the construction, which was useful for monitoring the evolution on the deformation state of the building.
Tra le numerose problematiche legate alla realizzazione di un alto edificio, sono di fondamentale importanza la scelta della tipologia strutturale, la definizione delle azioni sollecitanti di progetto ed il controllo in fase di esecuzione. Per quanto riguarda la scelta della tipologia strutturale, sono possibili tre diverse alternative di ossatura: 1. Nucleo in calcestruzzo armato e colonne in acciaio 2. Nucleo in calcestruzzo armato e colonne miste acciaio-calcestruzzo 3. Nucleo e colonne in calcestruzzo armato La scelta della tipologia strutturale si ripercuote sulle necessarie operazioni di controllo della geometria e delle quote di piano in fase di esecuzione. Questo perché il calcestruzzo ha un comportamento viscoelastico mentre l’acciaio è solo elastico. Il tasso di partecipazione del calcestruzzo del nucleo e del calcestruzzo delle colonne, inoltre, è differente. Le unioni, quindi, devono consentire i relativi spostamenti differenziali in verticale poiché salendo in elevazione bisogna prestare attenzione alle effettive quote di piano raggiunte in altezza dalle due parti strutturali, onde evitare successivi disallineamenti, peraltro dannosi per il comportamento statico e dinamico dell’intera struttura. Una corretta impostazione del problema richiede, in primo luogo, di introdurre il concetto di sequenza costruttiva. Gli edifici alti vengono costruiti attraverso ben definite sequenze temporali e un’analisi strutturale che prescinda da questo aspetto può portare ad una errata valutazione in fase progettuale. Quanto detto è stato affrontato nello studio del comportamento strutturale dell’UniCredit Tower a Milano, confrontando in primo luogo le azioni agenti su quattro colonne prese in altrettanti punti significativi, riferendosi ad un modello risolto in maniera convenzionale, a uno per fasi ed a uno per fasi con effetti della viscosità. L’analisi è stata poi estesa alla struttura globale, estendendo la valutazione delle fasi fino a 25 anni dopo il termine della costruzione, utile a monitorare l’evoluzione dello stato deformativo della struttura.
UniCredit tower. Analisi strutturale per fasi costruttive
CICIRIELLO, ANGELO
2018/2019
Abstract
Among the numerous issues connected to the construction of a tall building, it is of fundamental importance to take account of some elements, such as the choice of structural typology, the definition of the soliciting actions and the control on the execution phase. As regards the choice of structural typology, three different alternatives are possible: 1. Reinforced concrete core and steel columns 2. Reinforced concrete core and mixed steel-concrete columns 3. Both core and columns in reinforced concrete The choice of structural typology has repercussions for the required control operations of geometry and plan dimensions, applied at run time. This is all due to the fact that concrete has viscoelastic features, while steel it’s only elastic. Furthermore, the contribution rate of concrete either in the core or in the columns, is different. The structural unions, therefore, must allow the associated differential upright displacements. These devices are proposed in order to prevent misalignment, which is also damaging to both static and dynamic performance of the whole structure. A proper approach to this problem requires, first of all, an inclusion of the concept of sequence of construction. Tall buildings are erected by undergoing well defined time sequences; a structural analysis which ignores this aspect can lead to an incorrect evaluation during the design phase. This analyse has developed during a study on the structural behaviour of UniCredit Tower in Milan, comparing, in the first place, all the actions which affect four columns. This project was conducted with regard to three kind of models: one settled in a conventional manner, another in stages, and the last one in stages with effects on creep and shrinkage. Eventually, the examination was extended to the global structure, also evaluating phases extending up to 25 years after the end of the construction, which was useful for monitoring the evolution on the deformation state of the building.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/150822