GNGTS 2016 - Atti del 35° Convegno Nazionale

368 GNGTS 2016 S essione 2.2 Nakamura Y.; 1989: A method for dynamic characteristics estimation of subsurface using microtremor on the ground surface. Quarterly Report of Railway Technical Research Institute (RTRI), 30 (1), 25-33. Nigro F., Renda P. and Arisco G.; 2000: Tettonica recente nella Sicilia nord-occidentale e nelle Isole Egadi. Boll. Soc. Geol. It., 119 , 307-319. Panzera F., D’Amico S., Lotteri A., Galea P. & Lombardo G.; 2012: Seismic site response of unstable steep slope using noise measurements: the case study of Xemxija Bay area, Malta. Nat. Hazards Earth Syst. Sci., 12 (11), 3421-3431. Slaczka A., Nigro F., Renda P. and Favara R.; 2011: Lower Pleistocene deposits in East part of the Favignana Island, Sicily, Italy. Il Quaternario Italian Journal of Quaternary Sciences, 24 (2), 153-159. Vidale J.E.; 1986: Complex polarisation analysis of particle motion. Bull. Seism. Soc. Am., 76 , 1393-1405. Evaluation of the dynamical features of the Catania University building heritage S. Imposa 1 , G. Lombardo 1 , A. Nigro 2 , F. Panzera 1 , S. Grassi 1 1 Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università degli Studi di Catania, Italy 2 Ufficio Ri.S.P.E. (Rischio Sismico Patrimonio Edilizio), Università degli Studi di Catania, Italy Introduction. The level of building damage and its distribution during an earthquake is due to the combined effect of local site response, based on subsurface ground conditions, and the dynamic features of the structures. The fundamental vibration periods of buildings are in particular important for determining their seismic performance. The engineering practice usually evaluate such features through empirical relationships, that estimate the building resonant frequency as a function of either the height or the number of floors, or through numerical modeling (Messele and Tadese, 2002; Gallipoli et al. , 2009; Panzera et al. , 2013). However, the discrepancy between the actual performance of a structure and the expected values can sometimes be significant, so that only the acquisition of experimental data allows us to appreciate its real dynamic behavior. Performing such investigations is particular important in earthquake prone areas like Catania and have primarily to concern the edifices of significant public interest such as schools and hospitals. Catania is among cities in Italy having a high seismic hazard (Panzera et al. , 2011a, 2011b) and its seismic history is characterized by large events (1169, 1542, 1693) having a moment magnitude ranging from 6.2 and to 7.3 (Working Group CPTI, 2004). Its geo-lithologic features contribute also to the enhancement of seismic effects as observed in several studies (Faccioli and Pessina 2000; Panzera et al. , 2011, 2015), being the result of a complex setting with lateral heterogeneities at a local scale, due to the presence of volcanic and sedimentary units (Monaco et al. , 2000). In this frame, following the suggestions of the in effect regulations, the University of Catania has promoted and supported surveys aiming at evaluate the dynamic features of the buildings making up its assets. Therefore contributing to evaluate and reduce the vulnerability of all the University building heritage. Present study illustrate the example of investigations performed in the “Palazzo Boscarino”, where the Department of Juridical Sciences is located (Figs. 1a and 1b). Methodology. Simplified methods usually estimate the fundamental frequency of a building by postulating it as a function of its geometry and of its total height. In recent years, experimental techniques using either earthquake or ambient noise signals have been proposed to evaluate the dynamic parameters of buildings (Parolai et al. , 2005; Gallipoli et al. , 2008). The dynamic properties of an edifice are usually described through its natural frequency and the damping ratio (ζ). The latter parameter represents the energy loss of an oscillating system that can be either internal (material damping) or due to another system (radiated damping). The damping ratio is important in seismic design since it allows to evaluate the ability of a structure to dissipate