How are floating bridges built?

Floating bridges are not a new invention. In some form or another, they have been used to connect two land locations separated by a body of water for hundreds of years. 

For the most part, bridges that float have been used by the military, the government, or the transit system. 

Permanent floating bridges are usually constructed of huge watertight concrete pontoons that are linked solidly end to end, on top of which the surface roadway is created. But today, they can also be temporary and made of solid plastic or composite materials.

Thanks to a number of scientific advancements in materials, a floating bridge construction platform can simplify the building process and help homeowners access to land across a body of water.  

In any case, a floating bridge construction platform requires a lot of pre-work assessment in order to ensure a successful outcome. Factors to be considered before beginning a floating bridge project include the following:

• The distance across the body of the water. In reality, floating bridges are usually less than a mile in length; most are a half-mile.
• Will it be temporary or permanent? If there is an emergency, such as a hurricane, earthquake, war, or need for transport of military equipment or food just once, then a temporary floating bridge may suffice. But if it will connect or transport two communities forever, then a permanent structure is recommended.
• The depth of the water is vital as pontoons need to be anchored. This may not be possible in very deep water.
• The overall weather conditions are also very pertinent. If the area is constantly faced with fierce winds and hurricanes, the safety of the structure has to be taken into account (see more about this below).
• The type of materials that will be used for construction needs to be fully considered.
• The cost is almost always a factor.
• What type of weight will it support? Depending on the type of materials used for construction, the floating bridge may be useful for rail, foot traffic, or heavy construction equipment.
• Another question that should be asked is how frequently maintenance and inspection will be required?

THE CONSTRUCTION PROCESS

Once the analysis is completed, the steps in the construction of the floating bridge include the following:

• Make the individual bridge pontoons on land adjacent to the waterway.
• The pontoons are then floated on water and towed by barges to the site of the bridge construction.
• The pontoons are individually anchored to the waterbed and each other, starting from each end. Once the two edges meet, they are then joined together in the center.
• Hundreds of high-strength steel cables are used to hold the pontoons in place.

WHAT ELSE TO CONSIDER WHEN CONSTRUCTING A FLOATING BRIDGE?

The impact of the force of the wind and water waves has to be considered when designing a floating bridge. A key factor in the floating bridge construction is what is known as the “fetch.” 

The fetch is defined as the unobstructed distance over the water over which the wind travels to reach the bridge. Therefore, the longer the fetch, the more intense the effects of the wind and waves will be on the bridge. 

When the wind and wave forces are strong, they can cause the pontoons to heave, bend, and even rotate, which creates enormous stresses to the anchor system, the cable wires, and the pontoons. 

The pontoons are generally designed to withstand large amounts of stress. Still, a serious storm strong enough to cause cracks may permit water to enter, leading to leaks and perhaps even the eventual sinking of the bridge.

Thankfully, floating bridges are almost fully immune from earthquakes because they are not built directly on land. However, a wave, for example, from a strong tsunami, can damage the pontoons and the bridge. 

After centuries of building bridges that float, engineers now have the knowledge and the tools to construct safe floating bridges. In addition, with proper maintenance and inspection, this type of bridge can last many decades.