Seismic Response of Buildings with Uncertain-but-Bounded Mass Distribution

Elastic response of building subjected to seismic excitation exhibits discrepancies between the computed and actual response. This is due to uncertainty in mass and in stiffness distributions, foundation rotation, base rotational excitation and other sources of uncertainties. To take into account of these uncertainties, building codes introduce the so-called accidental eccentricity by introducing in every storey of the buildings an artificial eccentricity, perpendicularly to the direction of ground motion, of the centre of mass with respect to its nominal value. As a consequence several analyses of slightly modified systems have to be conducted in order to perform the seismic assessment of the structure. In this paper, in the framework of the interval analysis, a procedure for determining upper and lower bounds of the dynamic response of structures with uncertain-but-bounded mass distribution vibrating under either deterministic or stochastic input is proposed. The procedure requires the definition of a unique structural model so reducing the number of analyses to be performed. Numerical results showed a very good accuracy of the proposed procedure for all the cases analyzed.