Out of the box strengthening design of steel box girder for an existing tied‐arch bridge

The renovation of the 2^nd Van Brienenoord Bridge, planned in 2026‐2029, requires strengthening of the complete arch. Four thick steel strips were added on the web plates and assumed as stiffeners in the reduced cross‐sectional method. Investigation was done to verify if this is correct, as the new prEN1993‐1‐5 draft version classifies the strengthening strips as so called ‘weak’ longitudinal stiffeners.

A FE model of an arch segment was made to undertake a geometrically and materially nonlinear analysis with imperfections included, also referred to as a ‘GMNIA’. The arch segment was loaded incrementally by applied displacements until the limit strain of the steel on a fiber, or the maximum reaction force, was reached. The results were compared against the EN1993‐1‐5 methodology. Considering realistic ULS load cases, the GMNIA showed that the sections have about 9% more capacity. This confirmed the assumptions and strengthening design for the arch.