ANIDIS - L'ingegneria Sismica in Italia, ANIDIS 2013 - XV Convegno

Dimensione del carattere:  Piccola  Media  Grande

Prestazioni sismiche di strutture prefabbricate con connessioni trave-pilastro ad attrito

ANDREA TITI, FABIO BIONDINI, GIANDOMENICO TONIOLO

Ultima modifica: 2013-05-10

Sommario


Precast concrete structures are generally limited to two or three storeys and, particularly for industrial use, most of them consist of one-storey hinged frames. The structural members are generally prefabricated, and dry connections with mechanical devices between such members are adopted. Beam-to-column connections are usually hinged and designed to transfer shear only. The dissipative zones are located at the base of the columns, where plastic hinges are expected to develop when a strong earthquake occurs. For these systems, a capacity design based on a collapse mechanism involving the maximum number of storeys is required to optimise the seismic performance. Recent research investigations demonstrated that precast structures, under condition of a proper capacity design of connections, can achieve the same seismic performance of cast-in-place structures in terms of global strength and ductility. However, this result may not be achieved for structures with dry beam-to-column joints where the transmission of shear forces is entrusted only to friction. A large number of existing precast buildings in Italy includes this type of joint connections. For these structures, the combination of horizontal and vertical seismic excitations can lead the beam to lose the friction restraint and move out of the support at the top of the column. Such type of failure was observed under recent earthquakes in Italy, including the Emilia earthquake in 2012 where the use of dry-friction joints has been one of the main reasons for extensive damage and structural collapse of several industrial buildings. This study investigates the behaviour of precast structures with dry-friction joints under seismic excitation. A dry-friction modeling suitable for non-linear dynamic analysis is proposed, and case studies are presented to identify the most critical parameters affecting the seismic performance of this type of structures. The proposed modelling is expected to provide a useful support to the vulnerability assessment of existing precast structures, and to a proper design of seismic retrofitting interventions.


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