The effects of time-dependent phenomena on concrete prestressed girder bridges are investigated. The study concerns the case of bridges built directly in their final configuration and that of bridges built by a sequence of stages in which geometry, restraints, and loads vary until the final configuration is achieved. An analytical approach based on the principles of aging linear viscoelasticity and the age-adjusted effective modulus method is followed. The paper has two aims: the first is to provide an efficient and simplified tool for the evaluation of the structural response in the early stages of design; the second is to compare the results of the analyses on actual cases of bridges when different shrinkage and creep prediction models are used. Numerical applications show that the influence of stress redistribution on bending moments, attributable to the change in static schemes, is reduced by the load-balancing effect of the dead load and prestressing and that bending moment diagrams for bridges in service do not change significantly with the different prediction models. Opposite results are found on deflections, which differ significantly in reference to the model used. Differences between predictions models are underlined, suggesting that designers should manage them with prudence to predict the long-term performance of concrete. Finally, Eurocode predictions always underestimate final deflections and stress redistribution because of the static scheme variation.

In this paper, a study about stay stressing procedures of concrete arch bridges built by cantilevering with temporary stays is presented. Particularly, the partial elastic scheme method is proposed to find the initial cable forces, and a forward procedure is implemented to follow the actual sequence of construction by extending a procedure already applied to concrete cable–stayed bridges. The theoretical treatment is followed by a numerical application on a case study of a concrete arch bridge, and a comparison between initial cable forces found by the partial elastic scheme method and classical backward analysis is presented here. Results show the effectiveness of the proposed procedure to achieve the requested design geometry of the arch and for limiting the variation of bending moments and stay forces in construction stages.