Dynamic response of rocking components under building floor motions

under earthquake events. Most of seismic risk related to whole building systems is due to the vulnerability of such components; this is particularly significant for existing buildings and public facilities such as hospitals. A large part of contents and equipment of public and strategic buildings is often unanchored, and this is likely to exhibit rocking response under low-to-moderate intensity excitations. Several experimental studies proved that reduced base rotations of such components are likely to cause interaction with the surroundings, even leading to instable conditions. Therefore, moderate motion of rocking components can be more associated with significant damage and human losses rather than with serviceability conditions. Indeed, operational performance is even a matter of primary importance for all components of critical facilities, and for critical components of all buildings. The dynamic behavior of unanchored components is often modelled by using the rigid block approach. A large number of studies addressed the seismic response of rocking components through both experimental and numerical methods. However, ground accelerograms were often considered as base excitations, implicitly assuming the location of the components at the ground floor. In fact, the influence of both building features and component (height) location can be significant on the performance of rocking elements, which are extremely sensitive on the frequency contents of the base excitation. The present study investigates the dynamic response of a variety of unanchored components under real building floor motions. A wide spectrum of (a) structural features and (b) component (height) locations is considered. The Housner rigid block motion equations are numerically solved according to previously validated studies, and incremental analyses are performed up to the block overturning. The latest findings related to the response of rocking components are taken into account for the definition of the performance criteria as well as for the selection of efficient and reliable intensity measures for the damage analysis. The responses of the blocks subjected to the floor motions are compared to the numerical results of a past study that considered real strong ground motions as loading histories. The influence of the building system on the capacity of the blocks is finally assessed.