Abstract:
Nonstationary earthquakes are very complex ground motions and they vibrate structural
systems in asynchronous form. Spatial variation of an earthquake mainly originates from three
sources; loss of coherence effects, wave passage and local soil conditions. In this study, a longspan
bridge having multi-support excitations were analyzed for the effects of spatially varying
ground motions in terms of wave passage and local site response effects. Two types of dynamic
analyses were performed: a) same or different soil conditions for all supports b) same ground
motions but different arrival times for wave propagation. For evaluations, the results obtained by
considering asynchronous ground motions were compared with those of the synchronous ground
motions. From the comparisons, significant differences were observed in case of spatially
varying ground motions and this case show that the assumption of synchronous ground motions
and identical local site conditions are inadequate to represent the earthquake load and soil model.
Therefore, earthquake motions and actual local site properties should be characterized by their
inherent properties to obtain more realistic responses.
