Fragility of Bench-Mounted Equipment Considering Uncertain Parameters

This paper presents analytically developed seismic fragility curves for unattached bench-mounted equipment considering representative building, bench, and equipment interface properties. The emphasis of the study is on rigid scientific equipment, which is often placed on the surface of ceramic laboratory benches in science laboratories or other buildings. The paper first addresses the inherent uncertainty in the frictional behavior of the equipment supported on benches (defined by the static and kinetic coefficients of friction, ${\mu }_s$ and ${\mu }_k$ , respectively) and then describes the resulting variability of their sliding response when subjected to earthquake motions. Seismic fragility curves are generated for these types of equipment, considering 32 short distance ground motions of different hazard levels, propagated through three different building models. It is observed that although the variation in response is highly sensitive to the uncertainty in ${\mu }_s$ and ${\mu }_k$ , this variability does not propagate to the fragility curves. Moreover, accounting for the supporting bench and building characteristics are shown to significantly affect the shape and distribution of the fragility curves. From these results, considerations for design are proposed.