Heavy Loading Bailey Pontoon Floating Bridge For Emergency Situation

Floating Pontoon Bridge Description:

Floating pontoon bridge by boat or tank instead of bridge pier, the float bridge. Army together a using standard equipment, military pontoon bridge, says pontoon bridge. Its structure is not complex, open and convenient, bridge construction has the characteristics of simple, fast, but the high cost of maintenance. At ordinary times could be used in the emergency disaster relief or as a temporary traffic facilities.

The erection of pontoon bridge is a special specialty, which involves a lot of professional knowledge. This paper mainly introduces the structure, construction method and simple design method of pontoon bridge erected by highway steel bridge equipment.

Floating pontoon bridge design basic scheme consideration points

Road condition, performance, pontoon structure, pontoon drawings, environment

Basic design principle of floating pontoon bridge

Principles to be followed: the performance objectives are consistent with the purpose, safety, durability, quality, ease of maintenance and management, harmony with the environment, economy and other indicators.

Choosing the type of structure: topographic, geological and geographical conditions should be considered.

The number of pontoon structures and the overall system should meet the requirements of strength, deformation and stability.

Below table gives the classification of the status performance levels of the floating pontoon bridge. A state performance level of 0 is mainly compared to other performance levels 1-3. For traffic loads, storm waves, tsunamis and earthquakes, the pontoons are designed in several performance levels.

According to the importance factor, the design of the floating bridge should ensure that it has the corresponding target performance level listed in table, such as load, storm wave, tsunami and earthquake.

Floating pontoon bridge design load

Design load

It mainly includes: Static load, dynamic load, impact load (such as collision, etc.), earth pressure (such as the anchor pile in the anchoring system on the floating pontoon bridge), hydrostatic pressure (including buoyancy), wind load, water wave factor (including expansion factor), seismic factor (including hydrodynamic pressure), temperature change factor, water flow factor, tidal change factor, foundation deformation factor, support movement factor, etc. Snow load, centrifugal load, tsunami factor, storm tide factor, lake fluctuation (secondary fluctuation), ship shock wave, sea shock, braking load, assembly load, collision load (including ship collision), pack ice factor and pack ice pressure, coastal transport factor, drifting object factor, water class factor (erosion and friction) and other loads.

Combined load

The combined load will have an adverse effect on the floating pontoon bridge.

Tide levels are divided into the following categories:

During earthquakes: between H.W.L.(high water level) and L.W.L.(low water level);

During snowstorms: between H.H.W.L.(highest H.W.L.) and L.W.L. or between H.H.W.L. and L.L.W.L.(lowest L.W.L.);

Conditions of use: between H.W.L. and L.W.L.

Thus, no fatal damage occurs during tsunamis, either from extreme tidal changes between H.W.L. and L.W.L. or from rising and lowering water levels.

Features of Floating pontoon bridge 

1. The pontoon bridge can generally only form a single-lane, and the width for the vehicle is 3.7m. When the double lane bridge is needed, two bridge span devices are used side by side.

2. The main beam of the pontoon bridge is mainly hinged cantilever beam system. That is, the bridge gate bridge is connected with the main beam with an articulated connector.

3. Local strengthening and connection is usually required between the main beam of the pontoon bridge and the boat (boat) body.

The erection of pontoon bridge is a special specialty, which involves a lot of professional knowledge. This paper mainly introduces the structure, construction method and simple design method of pontoon bridge erected by highway steel bridge equipment.

Limit state of the floating pontoon bridge

The floating pontoon bridge should be have sufficient capacity to face potential hazards such as ships, debris, wood, floods, mooring rope failure, and complete separation of the bridge after lateral or oblique fracture.

Although the water provides buoyancy for the floating pontoon bridge, if the water leaks into the interior of the floating pontoon bridge, it will gradually damage the floating pontoon bridge and eventually lead to the sinking of the bridge. This is the current research problem facing the floating pontoon bridge.

Advantages of floating pontoon bridge:

Rapid deployment

Portability and reusability

Flexibility in design

Versatility

Specific design and analysis of floating pontoon bridge

Stability: refers to the ability of the ship to tilt under the action of external forces, and to return to the original balance position after the external forces disappear.

Three equilibrium states:

1) Stable balance: G is under M, and gravity and buoyancy form a stability torque after the tilt.

2) Unstable equilibrium: G is above M, and gravity and buoyancy form an overturning moment after tilting.

3) Accidental balance: G and M coincide, and gravity and buoyancy act on the same vertical line after tilt, without torque.

The relationship between stability and ship navigation:

1) The stability is too large, and the ship swings violently, causing discomfort to personnel, inconvenient use of navigation instruments, easy damage to hull structure, and easy displacement of cargo in the hold, thus endangering the safety of the ship.

2) The stability is too small, the ship's anti-capsizing ability is poor, it is easy to appear large inclination Angle, slow recovery, and the ship is tilted on the water surface for a long time, and the navigation is ineffective.

As with boats, the overturning of pontoons is related to their static stability.

Floating pontoon bridge body design:

General pontoons mainly consider the separate pontoon tank. As explained earlier, the hydrodynamic characteristics of each tank can be studied individually, and then the results obtained can be used for global system analysis. 

Design of wind speed and effective wave height: the effective wave height of 2.5m is a key point of the pontoon type bridge. In order to ensure that the effective wave height is below 2.5m, it is necessary to set up a wave barrier. The viscous effect and the potential flow effect are two important factors in the analysis of the incident water wave motion and the stress of underwater structures. For potential flow theory, it is mainly the scattering and radiation effects of water waves around the structure.

Application of floating pontoon bridge:

Pedestrian, road and railway.

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