Safety assessment of a CFRP retrofitted bridge

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 in Lombardia, is investigated. Around ten years ago a significant restoration was carried out due to the bad conditions of the infrastructure: the P/C beams were retrofitted by means of CFRP strips and the top slab over the two internal piers was 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. The discussion on the adopted procedure is the main goal of the paper.