Which is strongest a stone slab bridge or a wood frame bridge?
Stone is much more durable but its brittle and will fracture and break over relatively short spans (30 feet max). A long time ago stone slabs had given way to the stone arch which is not only stronger but can span much greater distances (up to 100 feet per span) Wood is flexible and wood frame bridge can span a 100 feet or more in between supports. Wood frame train trestles are heavily supported but can carry many tons across them. The big advantage with wood is the lower initial cost, ease of construction and the availability of trees. An open wooded bridge will last about 20 years, a covered bridge wooded bridge a 100 years or more. Many stone bridges have lasted for centuries.
