On the effect of multi-angle and spatially variable ground motions on cable-stayed bridges
The definition of the Spatial Variability of the Ground Motion (SVGM) is a com- plex and multi-parametric problem. Its effect on the seismic response of long and multiply-supported structures in general, and on cable-stayed bridges, in particular, is important but not entirely understood. This work examines the effect of the SVGM on the seismic response of cable-stayed bridges by means of the time delay of the earth- quake at different supports and of the loss of coherency of the seismic waves. The focus herein is the effect of the SVGM on cable-stayed bridges with various configu- rations in terms of their length and of design parameters, such as the pylon shape and the pylon–cable system configuration, combined with the influence of the incidence angle of the seismic waves. The aim of this paper is to provide general conclusions that are applicable to a wide range of cable-stayed bridges and to contribute to the ongoing effort to interpret and predict the effect of the SVGM. It has been found that the influence of the multi-support excitation on the seismic response of the bridges is strongly affected by the shape of the pylons, by the pylon–cable system configura- tion and by and the earthquake’s incidence angle. It is also observed that the SVGM excites vibration modes of the bridges that do not contribute to their seismic response when identical support motion is considered.