Probabilistic Response of Multi-support Structures on Non-uniform Soil Conditions

Conventional seismic design criteria take values of internal forced and other response variables as those provided by an envelope to the values of those variables produced by in-phase motion of all supports. In structures extended in plan, such as long bridges, or founded on heterogeneous formations or irregular topography, such as dams, differences in ground motion among different supports may give to differences as compared with those produced by conventional analysis. In this paper ground motion is represented as stochastic process with evolutionary intensity and frequency content. A criterion for determining design responses, based on the variance of the response of the structure is proposed. Proportionality criterion depends on cross-correlations between displacements and accelerations occurring at supports. The proposed criterion is illustrated by applying it to a continuous bridge supported on piles embedded in a variable depth layer of soft clay.