How do you build a bridge in timber?

  1. The wooden road bridge is built of massive laminated timber beams made by gluing sev­eral laminated timber beams in parallel. The beams are fixed to each other as construc­tion proceeds.
  2. Holes are drilled through the beams to receive metal ties which are tightened to a strain of 15 tonnes. At that point, the entire bridge deck be­gins to act as a single load-bearing panel.
  3. Water-proofing is laid on top of the deck with a 110-mm wearing layer of asphalt on top of that. On bridges for lightweight traffic, the wearing layer is 80-mm thick.
  4. The balustrades are screwed to stainless steel fix­ings in the joints between the beam structures. These fixings are always dimensioned to be weak­er than the load-bearing structure so that any col­lision with the balustrade does not have a delete­rious effect on the structure. If screwed joints are used they can be easily renewed when necessary. The balustrade construction is a standard detail also used in other bridges.
  5. The actual protection is given by separate wood cladding to provide a wearing layer which can be easily renewed when required. The load-bearing structures can be painted.