Surface generation of asynchronous seismic signals for the seismic response analysis of bridges

The seismic signals, recorded at different surface points during the propagation of the seismic waves through soil, show differences due to the soil-wave interaction. The seismic design actions should be evaluated properly in case of distant foundation points as these differences can be great. In this paper, asynchronous seismic signals are generated at surface starting from a few well-known recordings for the same seismic event. The EW accelerometric components of the main shock recorded at two recording stations (AQA, AQV) near L'Aquila city (Italy) on 4-06-2009 are the generation inputs. The seismic wave propagates along the direction between AQA and AQV. These signals are representative of a possible asynchronous excitation applied on a bridge. Five arrays of asynchronous accelerograms are generated at the foundations of the bridge to perform statistical elaboration of the results. Different bridge positions are supposed along the propagation direction of the wave to evaluate the spatial variability of the generated signals. The generated signals at AQA and AQV stations are compared with the available recordings at the same points (generation inputs) in term of power spectra, acceleration and displacement response spectra. Finally, the most detrimental soil distortions for the bridge deck are calculated for some bridge positions.