Timber Bridge Decks

The portion of the nation’s 500,000 bridge decks that are made of timber has been declining for years, as the old timber ones on secondary road bridges are rebuilt, in most cases with concrete. But some highway departments are finding that, in some situations, timber is the deck material of choice. In very short spans under 30 or 40 ft, deck-only timber “bridges” on low-traffic-volume roads are often the least costly acceptable alternative. A larger bridge near Pittsburgh needed its old timber deck replaced, and the decision was to re-deck in timber. It cost only half as much and is expected to last far longer. The Canadian province of Ontario has prestressed 15 timber bridge decks, some old and some new, and thus sharply increased their load capacity.