Methods for Extending Life of Existing Bridges: A Case Study

The Italian motorway and railway networks were built about 30 lo 40 years ago; they have a large number of prestressed concrete bridges and viaducts, most of these bridges must now be rehabilitated. External post-tensioning has been found to be a powerful tool for reparation, adjustment and for increasing the life extension of existing structures. Particularly this technique of reinforcement is applied with success to bridge structures, in many countries since the 1950s and has been found to provide an efficient and economic solution for a wide range of bridge types and conditions. The technique is growing in popularity because of the speed of construction and the minimal disruption to traffic flow. In response to the demand for faster and more efficient transportation systems, there has been a steady increase in the weight and volume of traffic throughout the world. As well as increases in legal vehicle loads, the over-loading of vehicles is a common problem and it must also be considered when designing or assessing bridges. As a result, many bridges are now required lo carry loads significantly greater than their original design loads. In the following, a study case of this technique will be illustrated on a railway bridge. During the construction of the railway line "Turin-Novara" (North of Italy), the Consortium Cav. TO-MI needed to utilize the bridge "Terdoppio" for the transit of the railway trains that had to serve to the placing of the equipment of the railway line. For the design of the reinforcement System, has been taken into account the presence of bonded and unbounded prestressing, also making use of some models of interaction between the different internal forces as recently proposed in literature. Today the bridge of "Terdoppio" is under service and the reinforcement has involved a substantial economy in the costs.