Assessment and retrofitting of existing bridges

The existing stock of road and railway bridges in Italy and in most European countries fre- quently exhibits insufficient performances, both in terms of structural safety and functionality, compared to the current demands coming from modern structural codes, transportation systems and necessity of reducing the costs of maintenance. Quick and reliable methodologies are then needed to assess the specific vulnerabili- ty of any bridge typology, in any possible environmental and operating conditions. In the first part of the pa- per the application of such type of methodologies to both road and railway transportation infrastructure in Ita- ly is described showing that, e.g., masonry arch bridges are usually quite robust structural systems, r.c. bridges generally present durability problems and are vulnerable to seismic actions, steel bridges, other than presenting durability problems, are particularly vulnerable to fatigue. Typical retrofitting interventions consi- dered in these studies are also briefly presented. In the second part of the work significant case studies of re- trofitting interventions are in more detail described, focusing on four existing r.c. bridges, which represent an homogeneous set, all of them being part of the post-IInd World War reconstruction on the Adige River (the second longest river in Italy). These bridges are examples of some of the most usual typologies adopted in that historic period, and the defects they evidenced after fifty years of service life were typical of these kind of structures, being often the consequences of a poor maintenance and the lack of durability rules in the original design. The refurbishment interventions are presented outlining a methodological approach, which takes into account the typological characteristics of the structure, the state of maintenance, the functional requirements and the environmental aspects connected to the repair and strengthening system.