The static principle of an arched bridge is that the vertical loads caused by the dead weight, traffic etc., are solely directed into the construction foundations through compressive forces in the arch. In this respect it is important for the construction foundations to be sufficiently strong so as to be able to absorb the vertical pressure on the arch.
The bridge consists of two arched laminated timber girders which are connected with horizontal timber tie members on a back-anchored basis. The truss posts are fitted between them. The supporting structure is at the level of the railings, so that the road surface is connected to the lower chord.
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*.
* Source: Redemption amounts calculation regulations - ABBV, BMVBS, status 2010 and study of DGfH 2006
Here is a selection of laminated timber arched bridges.