Experimental Investigation for Degradation Analysis of an RC Italian Viaduct and Retrofitting Design

The degradation state of RC bridge structures is one of the most important and difficult aspects to be interpreted. For these structures, structural analysis using FEM requires a reliable definition of the main mechanical properties of the materials constituting them and, in particular, a description of the actual damage state, which is a product of the damage they have suffered over the years. A general representation of material properties, including damage effects, can be performed by investigating the “global modulus (E)” of a structure. This can be determined by experimental determination of fundamental frequencies with an experimental analysis and the use of Rayleigh expressions. In this paper, referring to a practical case of a reinforced concrete Gerber beam with an advanced state of degradation, a static checkup was made using dynamic characterization. The state of the structure and its degradation due to corrosion and carbonation effects was analyzed using nondestructive and partially destructive tests. Moreover, dynamic tests were also performed to determine the fundamental frequencies (environmental trembling) to be used, through the Rayleigh method, to determine the global modulus of the structures, necessary for structural analysis. Then, a retrofitting design was designed and applied with partial reconstruction of the concrete deck by using high-performance concrete and by externally wrapping the main and secondary RC beams with carbon fiber-reinforced plastic (FRP) strips and wraps. Finally, a dynamic test was carried out to verify the efficiency of the retrofitting system adopted.