Simplified Expression for Seismic Fragility Estimation of Sliding-Dominated Equipment and Contents

Damage to small equipment and contents during seismic events has gained considerable attention following recent earthquakes, largely due to the potential for operational downtime, which results in significant economic losses. The estimation of losses from this interior building damage is a daunting task, due to the complexity of types of equipment and the randomness of their location within the structure. Nonetheless, a precursor to calculating such losses is a reasonable association between structural and nonstructural (equipment or contents) demands. Cast in a probabilistic framework, such an association is best represented through the use of seismic fragility curves, where the probabilities of exceeding a given damage state is correlated with an input parameter. In this paper, analytically developed seismic fragility curves for various unattached equipment and contents are calculated and presented. The emphasis of the study is on rigid scientific equipment and contents, which are often placed on the surface of ceramic laboratory benches in science laboratories or other buildings. Only uniaxial seismic excitation is considered to provide insight into the form of the fragility function. Generalized fragility curves are then developed and a simple expression is presented, which is envisioned to be very useful from a design perspective. The usefulness of the proposed expression is illustrated via a simple numerical example coupled with a design code-specified horizontal acceleration distribution profile for an example building structure.