Medium Girder Bridge

Medium Girder Bridge

Medium Girder Bridge

silhouette of bridge

MGB TECHNICAL SPECIFICATION

Construction

A single storey MGB bridge is constructed using top panels pinned together to form two girders and joined at each end by a bankseat beam, creating a rigid framework.

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Single Storey

In the Double Storey MGB, the girders consist of top and bottom panels, with junction panels and end taper panels forming the sloping end of the bridge. In both cases, ramp, deck and kerb units complete the construction.

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Double Storey

The MGB Link Reinforcement Set (LRS) consists of reinforcing links which are 3.66 metres (12ft) long, plus short links of 1.83 metres (6ft), which are pinned together to form chains under each girder.

Link Reinforcement


Double Storey Link Reinforced MGB

The Span Junction Set Construction

An MGB Span Junction Set

The MGB Span Junction Set consists of span junction posts, pinned together at the top and connected at the bottom by hydraulic articulators.

The Span Junction Set gives the Double Storey MGB a multi-span capability and allows bridges to be constructed over supports which are either fixed or floating. These may include any combination of existing supports, pontoons, existing or improvised piers and the MGB Portable Pier.

MGB Double Storey multi-span bridges take the form of two or three span structures rated at MLC 70(T). The two-span bridge can have an overall length of up to 51.5 metres (169ft), while the three-span can be 76 metres (250ft). This requires a total crew of 40 personnel — 24 for the main bridge, eight for the MGB Portable Pier and eight to install anchorages.

Floating MGBs

The versatility of the MGB system is shown by the adaptation of dry bridge components to a floating role.

Single and Double Storey Floating MGBs can be built using standard MGB superstructures, carried on MGB Pontoons with single storey hinge bays or double storey Span Junction Sets to provide articulation. The length of these bridges is limited only by the amount of equipment available.

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A floating MGB

Double storey construction allows landing bay spans up to 26.5 metres (86ft 11in) and is suitable for conditions where there is considerable rise and fall in water levels.

Single storey construction provides either floating bridges or ferries for load classes up to MLC 60(T).

MGB Pontoons

The MGB Pontoon is fabricated from marine grade aluminium alloy.

Two pontoons are coupled back to back to create each pontoon pier. Three piers make up one landing bay raft. Powered pontoons are driven by a 75HP diesel engine with a water jet propulsion unit. Fully laden pontoons can operate in currents up to 2.5m/sec (4.85 knots).

MACH MGB

The WFEL MACH building system

MACH MGB (Mechanically Aided Construction by Hand) is a semi-mechanised bridge building system which reduces the size of construction crews from 25 to nine personnel without needing additional build time.

This is achieved by prefabricating MGB components into modules in a separate assembly area. The bridge is then constructed using a suitable crane or HIAB vehicle. MACH MGB uses standard MGB components, supplemented by special components designed to assist mechanical handling.

The advantages of MACH MGB:

  • Any suitably sized crane can be used
  • Reduced manpower compared to standard MGB
  • The bridge can still be built by hand if required.

MGB Handrail

An MGB handrail

MGB handrails

The MGB Handrail compliments the use of the Medium Girder Bridge by adding a more substantial visible barrier to the edge of the bridge and is often deployed during more long-term civilian deployments.

MGB Product Application

MGB Product

Application

Single Storey

Up to 9.8 metre span at MLC 70 (T)

Double Storey

Up to 31.1 metre span at MLC 70 (T)

2 or 3 Multi-Span, Double Storey

2 span Up to 51.5 metres at MLC 70 (T)
3 span Up to 76 metres at MLC 70 (T)

Double Storey Link Reinforced Set

Up to 49.4 metre span at MLC 70 (T)* *Short Post

Floating MGB: Single Storey

Up to MLC 70 (T)

MACH (Mechanically Aided Construction by Hand)

For reduced manpower

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