A 16-Bay with LRS Medium Girder Bridge across the Kazer River, Mosul, Iraq, 2003.
RAPID FIELD CLASSIFICATION BOOKLET Purpose. Bridge and vehicle classification allows vehicle operators to avoid bridge failure due to overloading. Vehicle operators may drive across bridges without restrictions if their vehicles’ class numbers are less than or equal to the bridge class number. Field Manual (FM). This collection of publications is the single official repository for official Engineering Regulations (ERs), Engineering Circulars (ECs), Engineering Manuals (EMs) and other official public documents originating from Headquarters U.S. Army Corps of Engineers. A Bailey bridge is a type of portable, pre-fabricated, truss bridge.It was developed in 1940-1941 by the British for military use during the Second World War and saw extensive use by British, Canadian and US military engineering units.A Bailey bridge has the advantages of requiring no special tools or heavy equipment to assemble. M104 Wolverine Heavy Assault Bridge from 59th Engineer Company, 20th Engineer Battalion, U.S. The M104 Wolverine Heavy Assault Bridge is an armored military engineering vehicle created by General Dynamics Land Systems, designed to provide deployable bridge capability for units engaged in. Engineer company, multi-role bridge designation: engineer company (multi-role bridge) 1. To provide personnel and equipment to transport, assemble, disassemble, retrieve and maintain all standard u.s. Army bridging systems.
An M60A3 main battle tank crosses a medium girder bridge during Exercise REFORGER '83 in Germany, 1983
The Medium Girder Bridge (MGB) is a lightweight, man portable bridge and can be assembled without help from heavy equipment. In addition, it is also a deck type, two-girder bridging system capable of carrying loads up to and including Main battle tanks (MBT).
MGB was originally produced by Fairey Engineering Ltd., in Stockport England and is still made to this day by its successor WFEL based on a design by MVEE in Christchurch.
MGB was originally sold to the British Army in 1971, subsequently also being sold to many other nations, including the Dutch, Swiss, German and US Militaries.
- 3Configurations
Configurations and deployment[edit]
The primary components of the MGB system are rectangular 'top deck' segments, and triangular bracing 'bottom deck' segments. All segments are man portable.
Short/low load bridges can be constructed using just top deck components. Bracing with the additional lower deck dramatically strengthens the bridge allowing heavier loads and longer spans. Single spans can reach 48 metres.
The segments have knuckle joints at each end; assembly consists of simply engaging the knuckle joints of adjacent segments then inserting a pin through a hole down the length of the knuckle. In this way as many segments as are needed are connected end to end to form a girder of the required length to span the obstruction.
Two such longitudinal girders are constructed parallel to each other to provide the bridge's strength. Deck units are then laid between these to form a 4.0 m (13 ft 2 in) wide roadway.
MGB can be built in various configurations to provide a full range of bridging capability for use both in the forward battle area and in the communications zone. Speed of erection by the low number of soldiers is its major characteristic. The MGB also requires very little maintenance once erected, is air transportable in either standard palletised loads or in partially assembled bridge configurations, and all US components will fit MGBs in use by allies (except for the launching nose cross girder posts)
The bridge can be supported on unprepared and uneven ground without grillages. It is constructed on one roller beam for single-story construction; two roller beams, 4.6 m apart, for double-story construction; and on three roller beams when constructing a double-story bridge over 12 bays long. The ends of the roller beams are supported on base plates and each can be adjusted in height. No leveling or other preparation of the ground is required. Single-span bridges are launched using a centrally mounted launching nose.
Parts[edit]
The MGB parts are fabricated from a specially developed zinc, magnesium, and aluminiumalloy (DGFVE 232A). This enables a lightweight, high strength bridge to be built. All except three parts weigh under 200 kg. Most parts can be handled easily by four soldiers.
- Top Panel — Used to build the bridge girders. There are 7 panel points on each top panel; it is 6 ft 4 in (1.93 m) long, 2' 13⁄8' wide, 1' 95⁄8' high (1930 mm × 645 mm × 549 mm), weight 385 lb (175 kg).
- Bay (same as above)
- Bottom Panel — Used as a brace for bridge girders. it is 6 ft 5 in (1.96 m) long, 2' 3' wide, 3' 73⁄8' high, weight 435 lb (197 kg).
- End Taper Panel — Used as a bottom brace between the junction panel and bankseat beam. is 13' 25⁄8' long, 2'4' wide, 1'6' high, and weight 600 lb (270 kg). It is one component that requires at least 6 soldiers to carry
- Bankseat Beam — Used to keep the bridge girders properly spaced and provide connection for the ramp units. It is one of three components that requires at least 6 soldiers to carry; it is 13' 31⁄2' long, 1' 93⁄8' wide, and 1’ 6' high and weighs 570 lb (260 kg).
- Ramps — There are two types: US and UK ramps. The UK or short ramps are 264 lb (120 kg) and the US or long ramps are 400 lb (180 kg). Each type provides an approach to the bridge, 7 are required at each end. UK ramps are used for single storey only.
- Deck Unit — 9'1' long, 1' 51⁄4' wide, 67⁄8' high, weight 163 lb (74 kg) it requires 2 soldiers to carry. This component fills in the gap between girders. Four deck units are required per bay of bridge.
- Junction Panel — Used as a brace between the sloped and level part of a double story bridge. It is 5'3⁄4' high, 3' 51⁄2' long on top, 2' 23⁄4' long on the bottom, 2' 11⁄2' wide, weight 478 lb (217 kg).
- Sway Brace
- Kerb
Configurations[edit]
Single Storey[edit]
Up to 9.8 m span with a MLC of 130 wheeled or 85 tracked
The single storey MGB bridge is constructed using top panels which are pinned together to form two girders and joined at each end by a bank seat beam creating a rigid framework. This type of bridge is used for short span, that can carry heavy loads. Longer bridges are only able to carry lighter loads. Single-storey bridges can be constructed by 9 to 17 soldiers.
Double Storey[edit]
Up to 31.1 m span with a MLC of 100 wheeled or 70 tracked
In the double storey MGB bridge, 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 curb units complete the construction. The heavier duty double-storey configuration is used for heavy loads or longer spans. The normal building party for double-storey bridges is 25 soldiers.
Double Storey with Link Reinforcement[edit]
Up to 49.4 m span with a MLC of 100 wheeled or 70 tracked
The MGB Link Reinforcement Set (LRS) consists of reinforcing links which are 3.66 metres (12 ft) long, plus short links of 1.82 metres (6 ft), which are pinned together to form chains under each girder.
The chains are suspended 2 metres (6 ft 6 in) beneath each bottom chord of the bridge and tensioned after building, by pulling the reinforcing posts into the vertical position. This creates a fully reinforced structure.
The Link Reinforcement Set (LRS) is constructed when a long, high class type of bridge is required. The LRS deepens the girder and transfers the load throughout the length of the bridge. This type of construction requires a building party of 34 soldiers, and is built on three roller beams.
Although using an LRS provides a longer bridge span, it lowers the Military Load Class from 70 to 60. This prohibits the heavier vehicles in use by the military from crossing.
Multi-span Bridges[edit]
2 span double storey up to 51.5 m with a MLC of 70
3 span double storey up to 76 m with a MLC of 70
The MGB Span Junction Set consists of span junction posts, which are pinned together at the top and connected at the bottom by hydraulic articulators.
The Span Junction Set gives the MGB Double Storey bridge 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 usually take the form of two or three span structures rated at MLC 70. The two-span bridge can have an overall length of up to 51.5 metres (169 ft), while the three span can be 76 metres (250 ft). This requires a total crew of 40 personnel—24 for the main bridge, 8 for the MGB Portable Pier and 8 to install anchorages.
Floating MGB[edit]
Up to MLC of 60
Floating MGBs can be constructed in single or double storey configurations using the same components as the dry bridge configurations:
Army Bridging Manual 2016
- Double storey construction allows landing bay spans up to 26.5 metres (86 ft 11 in) 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.
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.
MGB pontoons
The MGB Pontoon is fabricated from marine grade aluminum alloy.
Two pontoons are coupled back to back to create each pontoon pier. Three such piers make up one landing bay raft. Powered pontoons are driven by a 75 hp (56 kW) diesel engine with a water jet propulsion unit. Fully laden pontoons can operate in currents up to 2.5 m/s (4.9 knots).
MACH MGB[edit]
MACH MGB (Mechanically Aided Construction by Hand) is a semi-mechanized bridge building system, which reduces the size of construction crews from 25 to 9, for similar build times.
This is achieved by preassembling MGB components into modules in a separate assembly area or moving them as whole modules of beams and lower panels plus a special junction module to the bridge site . The bridge is then constructed using a suitable crane or CALM vehicle.
MACH MGB uses standard MGB components supplemented by special components designed to assist mechanical handling.
The advantages of MACH MGB over other purpose-built mechanized systems are:
- Any suitably sized crane can be used.
- Reduced manpower compared to standard MGB.
- The bridge can still be built by hand if the crane or hydraulics are incapacitated.
- MACH MGB is field proven and used worldwide.
MGB handrail
The MGB handrail is designed to provide a significant increase in awareness of roadway width for both military and civilian drivers. It consists of vertical connecting posts with longitudinal hand rails, creating a continuous barrier along the edge of the bridge. Handrail components can be carried on an MGB palletor unit transport.
Construction[edit]
- Capsil Roller Beam of the Medium Girder Bridge. Used as an extension to the construction frame to roll the bridge out over the gap. Kazer River, Mosul, Iraq, 2003.
- Soldiers (299 MRBC USAR[1]) attach the link reinforcement set to the underside of the bottom panel
- Aerial view of the erection site of a Medium Girder Bridge over the Kazer River, Mosul, Iraq, 2003.
- The MGB launching nose suspended over the gap. Kazer River, Mosul, Iraq, 2003.
- Soldiers (299 MRBC) steady the launch nose of a Medium Girder Bridge during erection over the Kazer River, Mosul, Iraq, 2003.
- Aerial view of the nearly complete erection of a Medium Girder Bridge over the Kazer River, Mosul, Iraq, 2003.
- A view of the sway brace system of a Medium Girder Bridge before the decking is placed. Kazer River, Mosul, Iraq, 2003.
- A fully erected Medium Girder Bridge crosses its first traffic over the Kazer River, Mosul, Iraq, 2003.
Users[edit]
Over 500 bridges had been delivered to 40 countries.[2]
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See also[edit]
- Bailey bridge for another bridge type with mobile military application.
- Pontoon bridge for another bridge type with mobile military application
References[edit]
- US Army Field Manual: FM 5-212 [3]
- USMC C-14D06 MGB Student Handout [4][permanent dead link] (PDF)
- WFEL MGB Technical Information [5]
External links[edit]
Media related to Medium Girder Bridge at Wikimedia Commons
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Medium_Girder_Bridge&oldid=828418745'
CHAPTER 9
ENGINEER OPERATIONS
GENERAL
ERP OPERATIONS
Army Bridging Manual Youtube
ERPs ensure the effective use of the crossing means. ERPs and TCPs may be colocated to provide control for the river crossing. The CSC uses them to rapidly organize and move the unit through the crossing area.- Controlling vehicle movement.
RAFTING OPERATIONS
ERP personnel configure vehicles into raft loads and send them to the river to coincide with the arrival of an empty raft. Engineers brief crossing units before their arrival in the call-forward area to make this happen as rapidly as possible. The briefing covers the- An engineer from the squad running the ERP can brief vehicle crews and rehearse the movement signals with them. The staging area is an ideal place to do this, minimizing the time and effort spent organizing a crossing unit in the call-forward area. Otherwise, a separate ERP should handle this task.BRIDGE OPERATIONS
A bridge operation requires a continuous traffic flow to the river. Units must be briefed and sent to the crossing site quickly. To accomplish this, engineers brief at staging areas and check vehicle load classification and dimensional clearances. The briefings include the following rules:SWIMMING OPERATIONS
For swimming operations, ERP personnel have the necessary briefings and vehicle inspections. Crossing units are responsible for most preparations, but ERP personnel can assist with operations at the predip site that is established nearby and provide recovery assets. A briefing on swimming operations should include-ENGINEER CONTINGENCY BRIDGING OPERATIONS
ASSAULT BRIDGES, LONG-TERM USE
Ribbon-bridge operations normally last no longer than 72 hours. Having the ribbon bridge remain in operation beyond that time frame presents problems for the engineers that normally would not be experienced during a short duration. Equipment maintenance, anchorage systems, constant changes in the water level, and repair of approaches must be considered for long-term use of assault bridges.MAINTENANCE
As equipment remains in use during crossing operations, maintenance services become more difficult to manage. Time must be made to allow boats and bays to be recovered from the water and completely serviced and checked for unusual wear. The techniques discussed in Chapter 7 are applicable but must include complete recovery of the equipment and movement back to the EEP where the services can be done. To accomplish maintenance services without jeopardizing bridging operations, boats and their replacements must be carefully managed. This may require procuring more boats than authorized by the table(s) of organization and equipment (TOE) to permit continued crossing operations without distribution for maintenance.ANCHORAGE
All military bridges must be held in position by some anchorage system. Short-term anchorage is normally used for assault bridges, but if the bridge is required to remain operational for a longer period, the anchorage must be upgraded to provide long-term support. Anchorage of the ribbon bridge must occur if the bridge is used for long-term operation. During short-term crossings, boats maintain the bridge's stability against the current's velocity and keep the bridge from being damaged. However, as time permits, an anchorage system must be emplaced to provide continuous stability and provide relief for the number of boats required. Initially, the anchorage may consist of a combination of shore guys and boats. This method can still allow the bridge to be broken and permit barge river traffic access. Eventually, a semipermanent anchorage system, such as an overhead cable system, should be emplaced to keep the bridge secure.KEDGE ANCHORS
Kedge anchors lie in the streambed and are secured to the bridge bays with anchor lines. They are designed to sink with the stock lying flat and the fluke positioned to dig into the bottom. On hard bottoms, the kedge anchor is useless.SHORE GUYS
Shore guys are cables attached from the bridges to a deadman or similar holdfasts on the shore. Shore guys can be upstream or downstream provided that the maximum anticipated current (or reverse current for downstream systems) does not exceed 0.9 MPS. Shore guys can be used for any length of floating bridge provided that a 45-degree angle be maintained between the shore guy and the bridge centerline. COMBINATION OF KEDGE ANCHORS
AND SHORE GUYS
A combination system may be used for upstream or downstream anchorage systems in currents less than or equal to 1.5 MPS. When constructing a combination system, attach kedge anchors to every float and a shore guy to every sixth float.OVERHEAD CABLE
An overhead cable system consists of one or more tower-supported cables spanning the river parallel to the bridge. Each end of the overhead cable is secured to the shore, preferably through the use of a deadman. Bridle lines are used to connect each bay of the bridge to the overhead cable. The cable functions like a cable used in a suspension bridge, except that its final working position is inclined toward the bridge because of the force of the current on the bridge.TC 5-210 provides the specific criteria for the design of an overhead-cable anchorage system, to include the cable design, tower design and placement, and deadman design.
PROTECTIVE SYSTEMS
Floating bridges, particularly those that will remain in place for long periods of time, must be protected against severe weather conditions and enemy destruction. If flood conditions or heavy debris hamper bridging operations, removing of interior bays will reduce the lateral pressure on the bridge and allow the debris to pass downstream. If losing the bridge is imminent, release an end section and securely anchor the bridge parallel to the shore until conditions permit resuming bridging operations. As the river's width increases, simply add more interior bays to the bridge to compensate.ANTIMINE BOOM
This device is designed to stop any mines that are sent downstream toward the bridge. The antimine boom is placed far upstream to protect the other protective devices as well as the bridge. It consists of a number of logs or other large floating structures attached to a cable running across the river. Concertina is normally placed along the length of the boom.IMPACT BOOM
The impact boom is designed to withstand the impact of large natural or man-made debris and stop the enemy from attacking the bridge by boat. It is constructed by placing a series of floats and cables across the river. The cables absorb the impact of the debris or boat and restrain it until it can be removed or destroyed.ANTISWIMMER NET
This net is used to stop swimmers or underwater demolition teams from reaching the bridge. The net can be constructed by suspending a mesh or net barrier from an anchorage cable to the river's bottom. Concertina may also be connected to the cable and net to prevent swimmers from climbing over the net. The net must be firmly affixed to the river's bottom or enemy divers can easily go under the net. The antiswimmer net should also be placed on the downstream side of the bridge to prevent enemy divers from reaching the bridge from downstream.APPROACHES
Over a period of time, traffic flow at the same location will eventually wear the approaches down and make them unusable. Engineers incorporate repair of the entry and exit banks and the approaches leading to the crossing site into the crossing-operation plan. Initially, the approaches may be suitable to receive heavy traffic with little effect, but implementation of reinforcing the approaches must be done for long-term traffic. When inspecting approaches, consider the following: Matting and rock or gravel are the best suitable materials to use to support the approaches. Maneuver units that will have to conduct long-term crossing operations should develop procedures to requisition and deliver these materials to identified crossing-site locations. Reconnaissance teams can locate local quarries where rock and gravel can be obtained through coordination with the host country.LONG-TERM GAP-CROSSING C2
More than any other mobility task, gap crossing involves managing combat power, space, time, and terrain. The controlling headquarters must be flexible enough to react to any changes in the tactical situation and scheme of crossing. This is particularly difficult when involved with long-term operations in the same area of operations. Management of the crossing site, enemy considerations, traffic-control measures, and CSS must be synchronized for long-term activities and must not be based on less than a 72-hour period.MANAGEMENT
Traffic and movement control remain the responsibility of the C2 headquarters. Activities may direct that another unit take over the crossing operation and equipment as a whole or bring their own crossing equipment and personnel to relieve the existing units and permit them to move forward. All aspects of the operation must be covered when handing over the crossing site to the gaining unit-just as though they were conducting the crossing for the first time.ENEMY CONSIDERATIONS
Operation of a single crossing site over an extended period of time increases the possibility of enemy interdiction. The possible use of nuclear or chemical weapons against friendly crossing activities impacts on control procedures. To prevent the friendly elements from becoming targets, forces must cross the gap as swiftly as possible to minimize the concentration of forces on either side of the gap. The controlling headquarters also varies the crossing-site location to reduce enemy threat interdiction.TRAFFIC-CONTROL MEASURES
Staging- and holding-area control must be maintained. These areas must be located far enough away from the gap to facilitate rerouting and the use of alternate roads to crossing sites. Staging and holding areas on the far shore must be developed to handle the traffic as vehicles travel back across. New routes may be constructed and existing routes upgraded to improve traffic flow. Staging areas must be able to provide the following:COMBAT SERVICE SUPPORT
In a normal gap-crossing situation, the committed combat forces will be temporarily separated from their full CSS. For long-term gap-crossing operations, increased traffic flow for the service-support vehicles must be considered and controlled. Sufficient crossing sites and designated crossing times can ensure that priority is given to field trains and ensure that timely resupply operations are not hindered. Recovery of nonmission- capable equipment presents an additional problem for recovery teams transporting the equipment back to the near shore for direct-support maintenance support. Additionally, recovery resources should continue to be provided at both sides of the crossing sites so they can quickly recover a vehicle unable to cross and prevent delays.MULTIROLE BRIDGE COMPANY (MRBC)
ORGANIZATION
The MRBC will be a combination of a MGB company and an AFB company. The MRBC's structure consists of a company headquarters, two bridge platoons (one MGB and one AFB), and a support platoon. The support platoon consists of a platoon headquarters, an equipment maintenance section, and a bridge-site section. The new bridge transporter, the improved common bridge transporter (ICBT), is specifically designed to function in the MRBC. The palletized-load-system (PLS) trailer will be procured as a part of the HDSB to allow the transporting of both bridges simultaneously.BASIC CONCEPT
A typical operational mission would begin with a platoon responding to a mission with an initial basic load of the desired bridge. When it completes the bridge, the platoon moves to the next site, either picking up the next required bridge along the way or finding the bridge cached at either the engineer bridge park or the site it will be emplaced. As the forces advance, the bridges become the responsibility of the engineer units in the communications zone. As prefabricated bridging is replaced by nonstandard or more permanent bridging, the platoon responds to bridge-retrieval missions. Retrieved bridges will reenter the supply system or be stored in the unit's bridge supply yard. Bridging sets are a supply commodity and are handled as any other Class VII supplies (major end item).IMPLICATIONS
Because bridge sets are exceptionally heavy and tall and have many parts (some are small and easy to lose), they should be placed on pallets and shrink wrapped for transportability and accountability. The procedure to requisition and deliver bridges is essentially unchanged. The number of bridges needed is unaffected, since it is based on METT-T and not the bridge-company organization.TRAINING
Engineer units' training must reflect the dual bridge capability. Currently, bridge crewmen receive advanced individual training on both fixed and float bridges. However, once they are assigned to a unit, their collective training is only on the single-type bridge of that company. Under the MRBC concept, individual bridge crewmen and leaders must maintain their proficiency on both types of bridges. Bridge specialists must continue to be proficient in all types of prefabricated bridges. Critical branch interaction during war-gaming exercises must consider employing the MRBC in current training by implementing a variety of missions, either sequentially or simultaneously, to become more accustomed to its employment. Additionally, engineer company-grade officers and noncommissioned officers (NCOs) will have increased responsibility and will need to improve their technical proficiency.Army Bridging Manual 2017
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