Pellecchia, Davide (2022) Base isolation systems for seismic protection of rocking art objects: modelling and design. [Tesi di dottorato]

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Abstract

In this dissertation, the performance of the base isolation for the protection of freestanding rigid bodies is studied in depth. Particular emphasis is dedicated to the protection of art objects, notably statues, that require many stringent requirements for their safeguard. The dissertation examines the rocking behaviour when the base isolation is supported on the main types of elastomeric isolators, i.e. the Lead Rubber Bearings and High Damping Rubber Bearings, and special device named Wire Rope Isolators. The hysteretic response of the isolation system is modelled by means of an accurate uniaxial phenomenological model belonging to a class formulated by Vaiana et al. (2018), thus greatly improving the dynamic response accuracy of this highly nonlinear coupled system. The parameters of the proposed hysteretic model have a mechanical meaning that is clearer than those characterising the differential model used in some papers. In addition, we propose a new design process using an energy-based approach regarding the above-mentioned hysteretic model. Notably, we exploit the hysteretic model's algebraic nature to derive a formula that computes the energy dissipated per cycle by a closed-form expression. This can be particularly useful from a technical point of view. The design procedure consists of evaluating the small number of model’s parameters by a constrained optimisation problem, equating the energies dissipated by a linear viscous system and the isolator. In this way, the model parameters have been established on the basis of specific and clear criteria, in contrast to the majority of alternative hysteretic models, mostly the Bouc-Wen one, in which they are directly provided without justifying their values and the procedure used to obtain them.

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