Influence of the static friction on the seismic response of a building isolated with sliding bearings

Dynamic friction at the sliding surfaces is the leading parameter for energy dissipation. However, the use of the dynamic friction only for the design is a common mistake in practice. The study investigates the effect of the static coefficient of friction on the seismic response of a 4-storey framed building isolated with sliding bearings with curved surfaces. OpenSees software program is used for the analyses. The static friction force during the initial sticking of the bearing is simulated by means of mechanical fuses inserted at the base level of the building, while the isolators are modelled using standard isolator elements that incorporate the dependency of the kinetic coefficient of friction on the sliding velocity according to an exponential law. The analyses account for three sliding materials with different coefficient of friction, i.e. a low friction material, a moderate friction material and a high friction material, and for each material, three different ratios of static to kinetic coefficient of friction. The analyses demonstrate that disregarding the static friction can lead to unpredictable response of the isolation system and non-conservative evaluation of accelerations transferred to the superstructure