Investigating the Performance of a Degraded Prestressed Concrete Box Girder Half-joint Bridge in the Spirit of the Italian Guidelines

The paper investigates a paired pre-stressed box-girder concrete bridge, according to the framework suggested by the new Italian Guidelines for the risk assessment of existing bridges. The bridges, selected as case study within the research agreement signed by the FABRE Consortium and ANAS S.p.A. for first applications of the Italian Guidelines, present significant age-related degradation phenomena known to the Administrator, who decided for the bridges demolition and reconstruction. Visual inspections confirmed defects in the pre-stressing system, a permanent deflection of the deck, and cracks at half-joints, possibly due to pre-stressing loss and creep effects triggered by the poor quality of concrete. Also, preliminary safety verifications revealed not to meet code requirements in most cross-sections. Consequently, the most degraded bridge was closed. From March 2022, experimental campaigns have been performed by the FABRE Consortium and ANAS for improving their experience on the behaviour of old pre-stressed concrete bridges, as well as to control possible performance loss of the open bridge, sustaining the overall route traffic. The paper summarises these activities and presents some possible future investigations to be carried out before bridge demolition.