Modeling sliding and rocking freestanding building contents considering multidimensional planar floor motions

Abstract

Dynamics of freestanding building contents due to multidimensional planar floor motions is investigated. The building contents are simplified into single-degree-of-freedom rigid blocks allowed only to slide or rock on their supporting floors. Equations governing pure sliding and pure rocking motions of the blocks are derived. Various modes of motion associated with the sliding and rocking blocks are identified, and criteria for transitions between the modes are provided. An event-based solution scheme is adopted to solve the equations of motion taking into account the non-smooth nature of the problem. The proposed methodology is validated using data from existing research studies and Working Model 2D analysis results. Several case studies are performed to examine the effect of the multidimensional floor input motion on seismic response of sliding and rocking contents. It is shown that rotational floor input motion could significantly increase seismic demands on sliding and rocking contents, even altering their failure modes. In addition, seismic responses of freestanding building contents are strongly dependent on their initial positions on rocking floors, which is not the case with only translational floor motions.