Nonlinear analysis procedures for safety assessment of existing RC bridges under traffic loads

The in-service Italian infrastructural asset, mainly consisting of ordinary and pre-stressed reinforced concrete bridges, is affected by a significant obsolescence: many bridges overpassed their theoretical nominal life and did not experience any maintenance intervention. Such a critical scenario is even worse if it is additionally considered the increase of vehicular traffic that occurred in the last decades. From a management point of view, many structures needed restrictions on use due to their inadequacy to withstand the traffic load provided by the current codes. This is a direct consequence of accurate safety assessments of such structures. In the present paper, the opportunity to adopt nonlinear analyses for the safety assess-ment of existing reinforced concrete bridges is discussed. The safety-format pro-posed in EuroCode 2 for designing new reinforced concrete bridges and based on nonlinear analysis methodology is critically reviewed to consider its possible appli-cation to existing bridges. Then, the estimation of modelling uncertainty is pro-posed to define some acceptance criteria for the specific numerical solution strate-gy to be used, following the most recent international research outputs. Finally, a case study is addressed with the aim to compare linear and nonlinear results, the latter based on a calibration and verification of the adopted modelling strategy.