Experimental Examinations of Free-Standing Structures with/without Cushion Stoppers for the Suppression of the Residual Sliding Displacement

In this report, we experimentally examine the stopper design and structural response estimation that were established for a free-standing structure to suppress its residual sliding displacement without impairing the high performance of seismic damage mitigation. For this examination, we conducted a series of shake table experiments on a free-standing single-storey structure based on the graphite-lubricated sliding interface whose friction coefficient is about 0.2, as well as a conventional structure fixed to the ground. The conventional structure suffered severe structural damage due to the yielding of its structural components when excited by excitations with intensities of Lv 2, corresponding to a major earthquake in Japan, and its 1.4-fold. Contrarily, the free-standing structure did not suffer such damage under the same excitations, because of the base isolation effect of sliding. However, it had large residual sliding displacement (over 100 mm) after each excitation. Under the same excitations, the free-standing structure with cushion stoppers, which was made by following the stopper design, effectively restrained the residual sliding displacement around 10 mm, without losing the high preformation of seismic damage mitigation. In these experiments, the shear coefficients provided by the structural response estimation were sufficiently close to the actual values of the superstructures in the free-standing structures. This study clarified the effectiveness of the stopper design and structural response estimation in reducing the residual sliding displacement and maintaining the high performance of structural damage mitigation.