With trough bridges, the roadway slab isn’t arranged over the longitudinal girders like it is on a deck bridge, but is situated between the main girders and lower than the upper edge of the main girders. Trough bridges therefore stand out with a lower construction height and, among others, are used for railway bridges or with pedestrian or cycle path bridges over rivers.
Steel frames which are fitted to the interior or exterior of the construction reinforce the supporting structure. At the same time, railings can also be connected to the frame in order to achieve the required railing height of, for instance, 1.30 with cycle path bridges. Structural timber protection in the form of side casing from solid timber as well as sheet metal covering on the top side guarantee a long service life because the supporting structure is protected against the influence of weathering such as heavy rain or UV light. A variety of surfaces can be selected for the road surface. Timber decking is the cheapest option for the surface. Configurations using mastic asphalt or large format natural stone slabs are also possible, however.
Timber trough bridges stand out due to their high level of efficiency. With span widths of up to 35 m it is possible to realise cheaper and less sophisticated constructions which can be completely prefabricated in the factory and delivered directly to the building site as a finished construction.
With its casing on all sides, the structural protection of the timber is guaranteed and a long service life is guaranteed.