Description
The maintenance of existing bridges sometimes requires an intervention to increase their residual bearing capacity during their service life. The bridge strengthening can modify significantly the original structural behaviour, but in many cases the lack of a specialized standard for existing structures in the past prevented the designer to operate a suitable check of the updated performance. In the paper, an example of a three-span overpass, built in the sixties, located on the east shore of Maggiore Lake is investigated. The main aim is to check the serviceability and the ultimate limit states of the bridge when variable loads are applied. The bridge is a second category bridge, that means that no trucks with a total load exceeding 44t can freely cross the bridge. The bridge is a girder bridge 21.1 m long: the central span is 0.92 deep and 10 m long, while the external spans are 0.32 m deep and 5.4 m long. In 2013 a significant restoration was carried out due to the bad condition of the infrastructure. The eleven P/C beams, 0.8 m deep, were retrofitted by means of CFRP strips and the top slabs over the two internal piers were also strengthened by additional reinforcement. After a basic diagnostic aimed at verifying the mechanical characteristics declared in the documentation attached to the drawings and the pictures of the retrofitting intervention, a load test driven by a preventive structural analysis carried out by means of a linear elastic approach allowed to fix a control procedure aimed at guaranteeing the safety conditions in the future time.
