Assessment of an existing prestressed concrete bridge according to the partial factor method for existing structures (fib Bulletin 80)

The assessment of existing reinforced concrete structures is a critical aspect for engineers and practitioners. In particular, existing infrastructures, as bridges and viaducts, are extensively exposed to environmental actions, materials aging, degradation and variation of magnitude of traffic loads during their service life. Hence, to perform the assessment of existing structural systems assuming the same criteria conceived for the design (i.e., partial factor method – EN 1990) can result to be too conservative and, sometimes, leads to unnecessary and costly structural interventions. In this context, fib Bulletin 80 defines a new partial factor method suitable for the assessment of existing reinforced concrete structures and infrastructures accounting for their residual service life, information from in situ and laboratory tests, measurements of variable actions and reduced target reliability levels according to economical and human safety criteria. The methodologies proposed in fib Bulletin 80 have been applied to the assessment of an existing precast box section pre-stressed reinforced concrete bridge built in 90s and located in north of Italy. The results are compared to the outcomes from the assessment performed according to EN1990 and, finally, limits and advantages of fib Bulletin 80 methodologies are discussed. (paper)