Unexpected flange crippling of a newly built cyclist bridge

Encouragement of cycling is an effective way to reduce energy consumption by traffic. Cycling lanes will, to the greatest extent practicable, be built close to currently used traffic roads in order to establish new, swift lanes that require little space. Building near railroads appears acceptable for the latter, preferably by cantilevered structures atop existing bridges. In the event that this is not acceptable, separate bicycle bridges may be constructed next to the railroad bridges. On the Brussels Ring Highway, close to the Zaventem Airport, the latter was the situation. The oblique bearing points at the extremities of the straight‐ended sections, used to construct this bicycle bridge experienced torsional moments during installation. This resulted in distinct folds in the bottom flange of the closed cross‐section of one of the six bridge decks. Both global FE‐models and more detailed models were created to explain this. None could adequately account for the observed flange crippling. The crippling can only be explained by an unintentionally increased torsion, which may have occurred during the manipulation of the bridge's component elements. Additional thin metal strips have been added to this section of the bicycle bridge to restore its bearing capacity.