Insights into structural assessment and long-term effects of a post-tensioned multispan concrete box girder bridge with vertically prestressed internal joints

The study focuses on multi-span prestressed bridges, where time-dependent effects like creep, shrinkage and prestress losses can have a significant impact on long-term behaviour. Specifically, the paper analyses a bridge constructed with the balanced-cantilever method and presenting the peculiarity of vertically prestressed internal joints, which significantly influence the deformed shape and require proper modelling approaches. The testing campaign is fundamental to achieve a deepened awareness of the actual behaviour of the bridge and to correctly reproduce it through a Finite Element (FE) model. The constructed FE model accurately predicts actual and future deformations and stresses, and allows simulating the actual service conditions of the structure. The novelty of the work presented in this paper lies in the development of a detailed model specifically tailored for the analysed bridge typology, considering real construction stages and long-term phenomena of both steel and concrete. The model has reached a high level of validation through the comparison of the results with extensive in-situ tests and theoretical formulations, so as to be able to achieve insights and learn important lessons on the long-term structural behaviour of post-tensioned bridges with special internal connections.