Reliability of existing bridges without damage and deterioration

Abstract In many developing nations, most of the transportation infrastructure was constructed during the 1960s. Many bridges, having been operational for more than 50 years, have shown no signs of structural deterioration. In most cases, there are no project records, requiring engineers to assess these structures. The safety analysis of these structures, using the same criteria as for new constructions is proved unsatisfactory, given that the allowable deviations in design could be greater for structures already built, with high construction quality control, justifying a long period of good service. The current Brazilian code for bridges includes provisions for reducing partial safety factors for existing structures with many years of good service, based on the Eurocode prEN 1990-2 proposal. Applying reliability theory, this study evaluates the extent to which improved construction quality—defined as minimizing construction deviations and material property variability—can justify the good performance observed over the years. Furthermore, it explores the possibility of reducing the reference period for accidental loads from 50 years for new constructions to a shorter period. It is demonstrated that the reduction in load safety factors resulted in acceptable increases in reliability indices, maintaining safety in situations of bending and shear in reinforced concrete superstructures, even with the moving load increasing over time. Thus, it is possible to avoid the need for costly strengthening of structures that continue to perform well.