A Floating Bridge, also known as a Pontoon bridge is a type of bridge that uses floats or shallow -draft boats to support a a continuous deck for pedestrian and vehicle travel.
The buoyancy of the support limits the maximum load they can carry.
Floating bridges are made of large water -tight concrete pontoons rigidly end to end, upon which the road way is built.
Despite their heavy concrete composition, the weight of the water displaced by the pontoons is equal to the weight of the structure which allows the bridge to float.
The first ever floating bridge was designed and constructed in the United States Of America across Lake Washington, Seattle. It was constructed using concrete pontoons, this was in around 1930's.
Initially, most of the floating bridges we're constructed mainly for military purposes as history tells /explains.
Floating bridges were constructed for temporary use in most cases therefore it meant that it was easy to dismantle and transport for reassembling at a different location, hence making them suitable for military operations.
This days, or in recent days, Floating bridges are constructed permanently for all the people and vehicle movements and transportation. The floating bridges are made erected at around 70 meters above the sea level to allow ships and boats to pass underneath freely.
This is the standard height though it can be as the design of the engineer in some cases.
The length or how long the floating bridge will appear to be depends on where it is crossing across. If it is a large water body then the size of the bridge will be longer than that crossing a narrow water body.
Structural Design and Analysis of a Floating Bridge.
• Preliminary Design
It entails selection of the type, size and location of the Floating bridge.
This stage addresses such issues such as;
- Winds and Waves. A Floating bridge should be designed in a way that it isn't affected by wind or any waves from the sea/ocean.
- Earthquakes. A Floating bridge is designed such that in case of any earthquake, it is free from it.
- Tsunami effects are also addressed at this stage.
- Progressive Failure. A Floating bridge should not be designed to have progressive failures.
- Public Acceptance. A certain percentage of the surrounding population should publicly accept the floating bridge idea before it's construction.
- Riding comfort and convenience.
- Design Criteria is also lied down at this stage.
- Construction plan is also given out during the Preliminary design stage.
• Dynamic Analysis.
This involves the testing and evaluation of the Floating bridge by executing data in real-time. The objective is always to find errors in a structure (Floating bridge) while it is running, rather than by repeatedly examining the code offline.
• Frequency Domain Analysis.
This is based on the principles of naval architectures and the strip theory developed for use in predicting the response of ships to sea loads.
Steps involved in Frequency Domain Analysis include ;
- Computing the physical properties of the floating bridge.
- Computing hydrostatic stiffness.
- Computing hydrodynamic coefficients.
- Calculating the wind, wave and current loads and other loading terms.
- Building a finite element computer model of the floating bridge.
- Solving equations of motions.
- Performing spectral Analysis.
- Combining the maximum response with other loadings for final design.
• Fabrication and Construction
This is the final stage where the floating bridge is constructed by technicians, tested and authorized for local or international use.
The designer uses the above types of information to design and detail structural plans and Construction specifications. In case of vast and a major projects like the floating bridge, a series of maintenance during it operation is very vital go regularly extend the service life of the structure.
Maintenance and operation of the floating bridge.
This is done frequently with the help of a Manual. The Manual is developed at the beginning of preliminary design until and after construction of the Floating bridge.
Maintenance of the floating bridge is done by qualified people. Vocational training is given to then regularly to counter new challenges that may occur.
The Manual provides guidelines & procedures for regular inspection, maintenance and operation of the Floating bridge.
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