Dynamic Identification and Calibration of an Arch Steel Bridge Model for the Evaluation of Corrosion Effects

Abstract

Bridges play a crucial role as they are critical elements in several road networks. Recent trends in condition state assessment require to evaluate not only the seismic vulnerability and the load carrying capacity for increased traffic loads, but also the damage state due to decay and environmental effects. in order to evaluate the structural reliability of the bridge and define priority lists for interventions on the network. In the framework of a series of inspections carried out at a municipality level for the above mentioned aims, a numerical and experimental analysis was carried out on a historical steel deck arch bridge, called Paleocapa bridge, located in the historic city centre of Padova (Italy). Paleocapa bridge is composed by six arches and is highly vulnerable to traffic load, due to a widespread and advanced corrosion state. In order to study the effects of both internal and external boundaries and the loss of mass and stiffness due to steel corrosion a parametric modal analysis was implemented. The steel material was characterized through uniaxial tensile test and metallographic and chemical analysis, while a dynamic identification test of the bridge was performed in order to extract modal parameters, i.e. natural frequencies, damping ratios and mode shapes. Modal analysis pointed out a decoupled behaviour of arches and deck, and among the same arches, with a consequent significant decrease in load-bearing capacity. The calibrated FE model of the bridge was used to assess the seismic and static capacity of the structure. In particular, the latter was very critical; therefore, it was necessary to limit the transitable load on the deck, in agreement with the public authority.