Maintenance of road bridges and road equipments optimized by a good fatigue design

摘要

Several examples illustrate in the article the importance of affecting a right consideration to the fatigue question : to organize the maintenance of a road heritage, as well of course for the good design of new elements that will facilitate the future maintenance. The eurocodes give us the possibility to design new equipements regarding the fatigue caused by the wind for both lightning masts and sign bridges. Old equipments can be evaluated by fatigue calculation in order to guide their maintenance procedures or to decide remplacement. If these equipements fail, the road will not be closed during a long time, but accidents may occur that will affect the transport safety. The introduction of the fatigue design rules to the new sign bridges and lightning masts regarded as construction will thus increase the road safety. However, if a bridge collapses, the road may be closed during a longer time. For bridges, many fatigue details are classified in the eurocode 3 ( part 9 ) from tests. But some details that cannot be found in the eurocode, and must however be studied and evaluated by computation. The article presents an example where the fatigue class of the detail is evaluated thanks to a FE-modelization according to the 2008 IIW Fatigue Recommendations. Consequence of the bad design of the longitudinal stiffeners of bottom flange of a steel box girder are explained. The feedback of this accident made possible to improve the practice concerning this type of bridges avoiding discontinuity of T longitudinal stiffeners or preferring U longitudinal stiffeners.