External Post-Tensioning Retrofit and High- and Low-Cycle Fatigue Study of Connections and Joints in Steel-Concrete Box-Girder Bridges

This paper reports the study of a viaduct retrofit by means of external post-tensioning. The structure is a steel-concrete box-girder bridge and the retrofit has been necessary mainly owing to an advanced corrosion state which has affected the structural steel of the boxes. During the design two solutions have been conceived: i) cables with a parabolic development; ii) cables with a rectilinear development. The advantages and the drawbacks of these solutions designed by S.I.GE.S s.a.s. are here presented. In parallel with this problem, an on going study is being carried out on the: i) dynamic regime in order to identify the sensitive details; ii) validation of the Finite Element (FE) model by means of output-only ambient vibration tests; iii) optimization and physical testing of the critical details. This study is devoted to improve both the high- and low-cycle fatigue strength in steel-concrete box-girder bridges and the results achieved so far are here reported.