Economic Efficiency of Modern Timber Bridges - Life Expectancy and Costs of Maintenance

The life expectancy of buildings in normal structural engineering is 50 years. For bridges, however, it is 110 years for the abutment and typically 80 or 100 years for the superstructure. Due to the large number of bridges, the costs for new structures and maintenance of existing structures are rising considerably. To burden the economy as little as possible, the best possible economic efficiency is required. A long life expectancy together with low maintenance costs are therefore the two important factors for a positive economic efficiency calculation. On the basis of a new investigation with official verification, the following average annual maintenance costs based on construction costs were obtained for the superstructures from the representative quantity of over 50 timber bridges for: – bridges with closed road surface or sealing 0,7%; – bridges where the main beams have an upper and lateral protection, beams underneath the road surface with upper protection 0,6%. There is therefore an actual level of quality which is consistent with that of road bridges constructed from steel, reinforced or prestressed concrete. It could also be confirmed that in the case of protected timber bridges, no differentiation has to be made between foot or cycle bridges and road bridges. Road bridges are constructed in a very robust way and often have a closed road surface, usually in the form of an asphalt sealing.