The number of bridges approaching or exceeding their initial design life has been increasing dramatically. Meanwhile, bridges are withstanding an ever-increasing traffic volume, both in number and weight of vehicles. Analytical and numerical models can predict bridges’ response to traffic loads and their ultimate capacity with low uncertainties; however, such uncertainties increase as bridges age due to deterioration mechanisms. Non-destructive tests of material specimens and full-scale load tests allow for updating structural models and predicting bridges’ responses with higher accuracy. On-site load tests with different load levels provide different information on the bridge behaviour (e.g., elastic response, first-crack load, and ultimate capacity), which impact the model updating differently. This paper compares the observed response of the Alveo Vecchio viaduct, a prestressed concrete (PC) bridge subjected to a controlled load test up to its failure, with its predicted response provided by four structural models. The observed response is measured by an extensive structural health monitoring system, while the structural models are developed with different levels of refinement and uncertainty in the input parameters. This study gives an insight into the ultimate load-carrying capacity of existing PC bridges and their behaviour during a whole load test to failure. The results show that the load-carry capacity of the Alveo Vecchio viaduct is almost four times higher than the design load; likely, many other Italian highway bridges with similar structural characteristics have a similar capacity.

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