Analysis of dynamic coupling between spans of two multi-span bridges using ambient vibration measurements

Abstract

Dynamic coupling in weakly coupled multi-span bridges usually is not considered in their design, since the coupling effects normally leave the structure on the safe side by reducing the peak-peak deflection of each span under moving vehicles and trains. Nonetheless in the framework of vibration monitoring, these coupling effects require further investigation, since some well known non-destructive damage identification technique relies on the fact that occurrence of damage leads to changes in structural dynamic properties, which are very often also influenced by the coupling effects. In this study, ambient vibration measurements were performed for two representative cases in order to investigate the dynamic coupling effects of these bridges. One is a three-span prestressed concrete highway bridge. And the other one is a five-span steel-plate-girder railway bridge. The experimental results verify the influence of dynamic coupling between adjacent spans for these two bridges. From the first bridge, it is also found that global modes of this weakly coupled multi-span bridge are very sensitive to the relative stiffness changes of an individual span, e.g., caused by localized damage.status: publishe