BASE-ISOLATION TECHNOLOGY FOR EARTHQUAKE PROTECTION OF ART OBJECTS

In this paper the dynamic response of base-isolated block-like slender objects, such as statues, subjected to horizontal ground excitation is investigated. The structural model employed consists of a rigid block supported on a rigid base, beneath which the isolation system is accommodated. Assuming no sliding of the block relative to the supporting base, when subjected to ground excitation the system may exhibit two possible patterns of motion, namely pure translation, in which the system in its entirety oscillates horizontally (1 degree-of-freedom response), and rocking, in which the rigid block pivots on its edges with respect to the horizontally-moving base (2 degree-of-freedom response). The dynamic response of the system is strongly affected by the occurrence of impact between the block and the horizontally-moving base, as impact can modify not only the energy but also the degrees of freedom of the system by virtue of the discontinuity introduced in the response. Therefore, the critical role of impact in the dynamics of the system necessitates a rigorous formulation of the impact problem. In this study, a model governing impact from the rocking mode is derived from first principles using classical impact theory. Numerical results are obtained via an ad hoc computational scheme developed to determine the response of the system under horizontal ground excitation.