Effect of Spatial Variability and Propagation of Seismic Ground Motions on the Response of Multiply Supported Structures

Abstract

The response of lifelines, modeled as two- and three-span continuous symmetric beams of various lengths, subjected to partially and fully correlated seismic ground motions is examined. The partial correlation of the input motions consists of a term that characterizes the loss of coherence and a term that represents the apparent propagation (phase difference). The analysis suggests that the propagation effects may be neglected when the motions at the site exhibit loss of coherence; however, when the motions are coherent, phase differences may produce higher or lower response than the one induced by fully correlated motions, depending on whether the dominant modes are antisymmetric or symmetric at the location along the beam and for the response quantity (bending moment or shear force) under consideration.