Retrofitting and refurbishment of existing road bridges

The stock of existing road bridges in Italy and in most European countries exhibit insufficient performance, both in terms of structural safety and functionality, if compared to the demands of current structural codes, transportation systems and the necessity of reducing maintenance costs. Reliable methodologies are therefore needed in the assessment and design phase to address the specific type of vulnerability of each class of bridges. Establishing principles for the assessment and rehabilitation of existing structures is essential as repair and retrofitting require an approach that is substantially different from the design of new structures, and entail knowledge beyond the scope of design codes. The ultimate aim is to limit construction interventions to a strict minimum, a goal that is clearly in agreement with the principles of a sustainable development. In the present chapter the application of such methodologies to different road bridge types is described. Usual rehabilitation and retrofitting techniques for reinforced concrete, steel and masonry bridge typologies are presented, in connection with significant case studies, which showed deficiencies typical of such structures, due to poor maintenance as well as lack of durability rules in the original design, thus making the retrofitting descriptions suitable for considerations of a general order. The structural rehabilitation interventions described are usually coupled with functional refurbishments, and outline a methodological approach, which takes into account the typological characteristics of the structure, its state of maintenance, its functional requirements and the environmental aspects connected with the repair and strengthening systems.