Effects of non-synchronous ground motion induced by site conditions on the seismic response of multi-span viaducts

The paper focuses on the effects of the spatial variability of ground motion induced by local site conditions on the seismic response of multi-span viaducts on pile foundations. Analyses are performed accounting for the soil-structure interaction by means of the domain decomposition technique; the kinematic interaction problem is formulated in the frequency domain and lumped parameter models are adopted to reproduce the frequency-dependent behaviour of the soil-foundation system in the non-linear inertial interaction analysis. Effects of the non-synchronous seismic action on the seismic response of a long bridge founded on a soft soil deposit overlying an inclined bedrock are investigated. The seismic action is represented by real accelerograms and site analyses are performed to define the non-synchronous motion induced by local stratigraphic conditions at each pier. Comparisons with results achieved with synchronous seismic motions demonstrate the significance of site effects on the response of long bridges.