Suspension bridge types about each type of bridge. Provided the cables are of sufficiently high quality, suspension bridges are suitable for the longest spans. However, their construction costs are high, so that usually they are economical only for spans in excess of 1000 feet. Shorter spans often are constructed for aesthetic reasons. The economy of longer span suspension bridges is due to their relatively low weight, but because of the greater flexibility that comes with low weight these bridges are more suitable as road bridges than railroad bridges. Suspension bridge types A suspension bridge is any type of bridge that makes significant use
Pontoon bridge points. The "Palsey Pontoon" lasted until 1836 when it was replaced by the "Blanshard Pontoon" which comprised tin cylinders 3 feet wide and 22 feet long, placed 11 foot apart, making the pontoon very buoyant. The pontoon was tested with the Palsey Pontoon on the Medway. An alternative proposed by Charles Pasley comprised two copper canoes, each 2 foot 8 inches wide and 22 foot long and coming in two sections which were fastened side by side to make a double canoe raft. Copper was used in preference to fast-corroding tin. Lashed at 10 foot centres, these were good for