The phenomenon of veering in the assessment of r.c. arch bridges

In this paper, possible sources of eigenvalue curve veering in arch bridges are sought. First, curve veering for an existing r.c. arch bridge is shown to be the effect of either a change in the elastic modulus of concrete, or the presence of zones with different stiffness. Then, the theoretical analysis of this phenomenon is carried out for an arch where a small region exists with elastic properties different from the remaining structure. The former example is meant to show that real arch bridges can be prone to the eigenvalue curve veering; hence, the experimental observation of veering should effectively address the identification of the structural parameters. In addition, the latter example suggests that, in some instances, localized damage in an existing bridge can be identified through the occurrence of eigenvalue curve veering.