Performance of nonstructural components in triple friction pendulum base-isolated buildings

Abstract

Recent earthquakes indicated that poorly performing nonstructural components cause the majority of consequential injuries, economic losses, and disruption of structural functionality, especially in critical facilities. This research investigates the seismic behavior of nonstructural components in a triple friction pendulum (TFP) base-isolated medical facility under three dimensional (3D) earthquakes. A hypothetical four-story reinforced concrete TFP base-isolated hospital building was created in SAP2000 to examine the performance of its nonstructural components when subjected to 3D ground motions. The base-isolated building model was analyzed to obtain floor accelerations for a suite of 11 ground motion pairs including their vertical components. These floor accelerations in the vertical and horizontal directions were then employed as excitations for the rocking response of rigid blocks, corresponding to different unanchored acceleration-sensitive building contents. The rigid blocks with various slenderness and size were compared to study their rocking response when subjected to horizontal only and horizontal-vertical (H-V) floor accelerations. Additionally, the slab center absolute vertical accelerations were compared for classification in terms of their peak acceleration values associated with nonstructural damage. The Horizontal-Vertical coupling effect in the floor accelerations due to 3D ground motions had a substantial effect on the rocking response of the nonstructural contents in comparison to the horizontal only floor accelerations. Although the relatively larger and stockier blocks were clearly less influenced, the comparably small and slender contents were greatly affected by the H-V coupling response in terms of their rocking, toppling, and jumping behavior. Consequently, the H-V coupling effect needs to be carefully evaluated for critical facilities, especially the friction pendulum-type base-isolated buildings, regarding the assessment of their seismic performance of nonstructural components.