Arched bridges made from laminated timber

Arched bridges are especially suitable for span widths of 20 to 70 m.

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.

Characteristics of arched bridges

High supporting capability with low cross section widths
Constructed with two arched laminated timber girders which can be connected with back-anchored horizontal timber tie members
Supporting structures is at the level of the railings
Bracing occurs in the form of a U-shaped steel frame
Road surface is connected to cross beams and is independent of the main structure
Railings fitted to the side of the arched girders or on the top of the cross beams
Covering of the laminated timber girders with titanium zinc plating for optimum protection against the weathering
Optimum solution for span widths of up to 50 m
Various road surface designs possible with timber decking or sealed in the form of a mastic asphalt layer etc.

Protected main supporting structure

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