Effect of Horizontal-Vertical Coupling on the Seismic Performance of Unanchored Nonstructural Components in a Triple Friction Pendulum Base-Isolated Building

Abstract

The coupling behavior in the structural response caused by the multicomponents of ground motions in friction pendulum base-isolated buildings can change the response of nonstructural contents. This research investigates the seismic performance of freestanding nonstructural components in a hypothetical 4-story reinforced concrete triple friction pendulum (TFP) base-isolated medical facility using a suite of 11 ground-motion pairs, including their vertical components. Floor accelerations in vertical and horizontal directions were employed as excitation for the rocking response of rigid blocks. In comparison with the horizontal-only floor accelerations, the horizontal-vertical (H-V) coupling behavior in the floor accelerations had a substantial effect on the rocking response of nonstructural contents, small and slender ones in particular. Consequently, the direct effect of vertical ground motions and the H-V coupling phenomenon on the seismic performance of nonstructural components need to be carefully evaluated for critical facilities, especially the friction pendulum–type base-isolated buildings, to quantify the damage level of unanchored components.