New bicycle and pedestrian bridge over the old Aare river, Lyss

The project
One of the numerous bridges connecting Lyss over the old Aare river to the recreational area in the Seeland region had reached the end of its service life. Among other things, rot had been detected in the wooden components because they were very close to the water. The specification for the new bridge near the Grien sports center was that it should not only be used as a pedestrian bridge, but also by cyclists. Compared to the previous crossing, the new bridge had to have a much wider roadway so that cyclists could cross without danger. Specifically, the previous bridge was only 1.80 meters wide, while the new one has a usable width of 2.40 meters.

The challenge
The new bridge had to fit onto the foundation of the original crossing, so the support situation of the abutments had to be taken over. The new bridge was designed as a trough bridge. The primary structure consists of two glulam girders. The steel cross girders are attached to the primary girders from below with glued-in threaded rods. Thanks to this flexurally rigid connection, the primary girder is stabilized and cannot tilt. The longitudinal girders of the carriageway are made of larch laminated timber, the decking of oak. With the new bridge, there is more space between the water and the bridge than before - an advantage during floods. Previously, there was a risk of driftwood piling up, damaging the bridge and flooding the adjacent land.