Uses and Construction of a Pontoon Bridge
A pontoon bridge is a suspended bridge with floating structures, known as pontoons, to support it. The pontoons are buoyant enough to hold up the bridge and its load. A pontoon bridge is typically built as a temporary structure but some can last for good amount of time.
An ideal location for a permanent pontoon bridge is in a covered water crossing where it is not practical to install a suspended bridge from an anchored dock. Such a bridge may need some elevation or some section of it may be removed to allow the passage of ships.
A pontoon bridge is particularly useful as a river crossing, especially during a war. At such a time, troops can make use of the pontoon bridge to easily cross a river and then destroy the bridge - or disassemble and carry it - afterwards so their enemies cannot follow them.
The design of a pontoon bridge should always take into account the maximum weight that it is expected to support. It is very important to remember that a pontoon can only support a total weight that is equivalent to the mass of the displaced water and that the weight of the bridge itself should always be calculated into the total weight. If a section of the bridge exceeds its maximum load capacity then the pontoon supporting that section will sink. It is also important for the path across each pontoon to be made of lightweight material for easy carrying but strong enough to support the expected load.
Before the modern day pontoon bridge was developed, wood was the typical material used in the construction of a floating bridge or a pontoon bridge. A wooden pontoon bridge is built in sections from an anchored starting point ashore. A pontoon was usually made from boats, timber rafts, or wooden barrels tied together. Each section of the pontoon bridge consisted of a single or several pontoons, which were arranged into position and then secured with an anchor. Wooden beams known as balks were used to link the pontoons together and then several cross planks are used to cover the balks and form a path. Railings are fixed on the side to keep the planks in place. This process is repeated until the pontoon bridge is complete.
Certain precautions are necessary to keep a pontoon bridge from potential damage and to ensure safety of individuals boarding the bridge. It is important to be mindful of the bridge's capacity because a pontoon bridge can be put out of place or flooded when the load exceeds the maximum limit. Overloading can also happen when a section of the pontoon bridge is supporting heavier load than the others.
Proper maintenance should include regular inspections to make sure the bridge is swaying normally or that there are no accumulation of objects on the pontoons that can damage the bridge.
