PSI - Issue 29

Michela Monaco et al. / Procedia Structural Integrity 29 (2020) 134–141 Michela Monaco et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction The rela tionship between exhibitions and museumaudiences has strongly changed in recent years (Black, 2012). In an ongoingattempt to engage people andmaintainaudiences, newmuseums as well as thoseunder renovationhave acknowledged the importance of offeringcreative spaces. Today’s audiences are no longer looking for a cold ‘white cube’museum experience (Nardi, 2008). Instead, they are looking forwarmer, shared experiences, i.e. people canbe closer to the artifact and even touch it (Candlin, 2017). This has induced a ttempts to exhibit museum artifacts in differentways. Nevertheless theexhibitiondevicesformuseums ought to be designedor strengthened to complywith the need of safety not only for the artifact but a lso for the visitors, in the sense established by current codes and regula tions (FEMA528). Due to the complex nature of exhibitions in subsequent types of museums there exist a need to match the proper techniques and methods of securing museum objects from damage individually (Ishiyama,1982). In particular, a lthough the roots of the problem of horizontal actions at the base of statues and vases lie down in the first years of sixties, a complete andeffective solution is far from being found. The reference model for the rocking responseof a rigid object supported on a base subjected to horizontal motion was in fact developed a t the beginning of ’60 considering the structure an inverted pendulum (Housner, 1963). The research was a imed mainly to model the behaviour of tall, slender structures during seismic events. Since Housner seminal paper, only recently the resilience of the buildings contents, art objects in museums, hospital devices or furnitures in earthquake affectedareas has been examined based on the Housnermodel. An artifact can be in fact considered as a rigid object simply supportedona movingbase that mayenter a rockingmotion and result in overturning. Acompletemodel of the problem involves the filte r’s effect due to thestructure of the building, that in some cases is itself part of CulturalHeritage (Monaco et al., 2018). In the seismic case the response of artifacts signif icantly depends in fact onboth the dynamic characteristics of the objects themselves and thebuilding in which they arearranged (GesualdoandMonaco, 2010). Abasic step towards addressing the problem envisages an accurate evaluation of the behaviour of the artifacts considering the dynamic filtering effect of the building structure. In fact, the ground motion that a building is subjected to undergoes a modificationof its dynamic characteristics during the propagation from thefoundationup to the baseo f the artifact at the exhibit floor (Buonocore et a l., 2014). It is necessary to preserve the cultural heritage formulating simple design rules to be followed when setting up a newMuseum or renovating one in a seismic area. A grea t problem is in fact represented by the costs of a safeguard system. The complexityof the problem increases in case of two superimposed rigid bodies. Psycharis (1990) assumed simplifications for thehighly nonlinear formulationwhile Spanos et a l. (2001) considered large friction coefficients, so tha t only rockingmotionwas examined. In manycases large friction values are not rea listic (Monacoet a l., 2014; Viti et a l., 2020). Rockingbehaviour canproducedamage a t the baseof themuseumartifact, especially in case of very fragile vases and statues(Pintucchi et al., 2019), while slidingmotion in some cases couldbea desiredcondition, taking intoaccount the distancewith themuseumor showcase walls andbetween the objects themselves (Gesualdoet al. 2018a). Incases in which the object is a unique one, like the Riace Bronzes, the design of on purpose isola tion systems is justified (Di Egidio et a l., 2019), while in genera l showcases and pedestals actually present in museums are not equipped with devices capable of decoupling thepedestal from themoving floor (Gesualdo et al., 2017). The protectionof small objects couldbe performedvia a simple and low-cost system, taking intoaccount their real conditions and way of exhibition. Experimental tests in these cases are a powerful tool, to assess the values of the mechanical parameters to be used in the numerical analyses (Gesualdo et a l., 2018b). Although several experimental tests are present in litera ture (Petrone et a l., 2017; Wittich et al., 2015), they are mainly addressed to examine the rocking behaviour, as well as numerical and experimental papers (Psycharis et a l., 2000; Ther and Kollar, 2018). In genera l, the protective measures that canbe taken for the numerous objects contained within any Museumshouldbe efficient, economic and simple, to be used by non-specialized workers (Guadagnuolo and Paolillo, 2012; De Matteis et a l., 2019; Cerri et a l., 2018). This paper addresses this last issue, giving contribute toward the design of exhibit criteria where characteristics ofmass, geometry and frictioncoefficient with thesupport in order to reduce the risk of overturning or impact with the surrounding wa lls in case of seismic events (Gesualdo et al., 2014). The numerical procedure developed to design the pedestal, depending on the object and the site mechanical parameters, is able to give indica tions about its needand the optimal placement of themarble statue.