Their special design makes them into an architectural jewel: Lattice bridges are part of the scenery in many regions.
The lattice elements are contiguous supporting structures. They offer the advantage that they have a lower material consumption than comparable full-wall constructions such as beams and they accordingly have a lower tare weight. The construction generally consists of laminated timber for the upper chord, lower chord and posts, and is mostly braced horizontally with steel diagonals. The roadway is connected to the lower chord. Lattice bridges typically have a low construction height.
Structural timber protection is the key to the longevity of a timber bridge. Structural timber protection intends for all structural timber components to be completely protected. In this respect, the following steps are taken into consideration: Installation of technically dried timber with a timber humidity of 12% in order to prevent insect infestation, protection against weathering, ingress of moisture, UV rays due to the installation of projections and skirting in the design as well as good air circulation to encourage drying out. Constructions designed in this way satisfy the requirements of protected timber bridges pursuant to DIN EN 1995-2 NA. This means that loss events are prevented and maintenance costs are minimised, and the use of timber preserving chemicals can be reduced and/or avoided. Structures protected according to DIN EN 1995-2 have a service life of 60 - 80 years*. With lattice bridges, the protection of the supporting structure is generally guaranteed by the casing, which is the cover and the additional side formwork.
* Source: Redemption amounts calculation regulations - ABBV, BMVBS, status 2010 and study of DGfH 2006
Here is a selection of lattice bridges in the timber design.