Portable and Adaptable Tactical Bridge Apparatus
Every day, engineers at the ERDC Coastal & Hydraulics Laboratory (CHL) are searching for innovative ways to adapt and apply military technologies to humanitarian assistance and disaster relief operations. The Lightweight Modular Causeway System (LMCS) is one such technology, which when fielded, will provide a versatile capability for military and disaster response planners.
Easy Rapid Deployment for Challenging Logistics
Prior to 2006, existing causeway systems did not meet the US armed services’ rapidly deployable force projection requirements. They were heavy, needed large deep-draft vessels with high-load capacity cranes to transport and unload them, and required extensive time and manpower to operationally deploy.
CHL engineers developed the LMCS concept to upgrade and replace existing systems, merging ideas from both conventional floating causeways and modern tactical bridges. They designed and built the LMCS with many critical core technological advancements:
- New double compressive joint based on high durometer urethane elastomers provides dependable repetitive compliance with minimal fatigue
- Durable joint material (similar to material used to buffer building motions during earthquakes) helps support large weight requirements (M1A2 main battle tank, for example.)
- Compatible with existing military container and cargo handling equipment and weighs only 600 pounds per linear foot
The innovative design of the LMCS consists of three key parts: superstructure, flotation elements (large inflatable tubes) and compliant two-way compressive connections. Because of this design, engineers and builders can emplace the LCMS without a shore-based staging facility. This makes the LMCS adaptable and flexible for applications in challenging physical settings, such as a post-disaster area where severe weather or earthquakes may have degraded existing port facilities.
Most Advanced and Efficient Superstructure of Its Kind
For a floating structural system like the LMCS, engineers designed a compliant superstructure to better distribute loadings to the floatation elements. By taking full advantage of the floatation, the internal bending stresses within the superstructure are reduced, allowing for a more efficient superstructure design. At present, only 120 feet of LMCS has been fabricated.
The system is designed with inflatable buoyancy elements and it also includes substantial reserves for ideal floatation if needed. This makes the LMCS design the most advanced of its kind with a variety of applications:
- Allows easy deployment even across shallow areas, such as mudflats near a coast
- Provides a rapidly-delivered and emplaced temporary floating causeway that allows shorter logistical lines of communication
- Provides expedient egress routes for evacuations and rapid interim replacements for bridges damaged by storms or terrorist actions. (No similar capability presently exists to meet these needs.)
- Transports easily and is rapidly employable from the armed forces’ Joint High Speed Vessels (JHSV). (Does not require “in water” connections.)
- Features an adjustable end module that can serve as a ramp section to allow rapid transition for water to shore, enabling vessels, like the JHSV, to access numerous small ports, greatly improving force projection and logistics support operations
CHL engineers have tested the performance of LMCS in a variety of real-world scenarios. They have demonstrated the great potential of LMCS as a vessel to shore bridging system, an expedient wet gap crossing asset, and for humanitarian assistance and disaster relief operations in areas damaged by severe weather events or earthquakes.
In June 2008 at Fort Eustis, Virginia and in September 2008 at Oahu, Hawaii, engineers conducted demonstrations which featured the use of LMCS as a shore-based floating causeway to enable Roll On/Roll Off logistics operations. A Logistics Supply Vessel was used as the marine platform, and the LMCS successfully supported traffic by both military and commercial vehicles. The versatility of the LMCS was also shown at a protected bare beach site at Fort Eustis. By partially deflating some of the pneumatic tubes on the shoreward side of the LMCS, the small deployment crew was able to increase the penetration of the causeway onto the shore. This capability also allows the LMCS to conform to existing bottom slope on the beach and limits extensive beach or shore preparation requirements.
In August 2009, engineers used LMCS to provide a rapidly installed expedient crossing of the Kumumauu Canal on Hickam Air Force Base in Oahu, Hawaii. This demonstration featured the transit of several vehicles that simulated a disaster relief force and included a 40-ton fire truck.
LMCS played a part in the major exercise Arctic Edge 2010 in Fort Richardson, Alaska. In this exercise, soldiers used organic equipment to rapidly deploy the LMCS across the Eagle River to provide a rapidly emplaced bypass for an existing bridge that had been damaged by a simulated earthquake in the exercise scenario. The demonstration featured the helicopter transportability/employability of LMCS and the ability of engineer troops without significant LMCS experience to employ the system as bridging in a fast moving river. A CH-47 Chinook helicopter was successfully used to sling load and fly two LMCS sections. Twenty members of the 6th Engineer Battalion successfully emplaced seven LMCS modules to span the 70-foot gap across the river.
The LMCS Program received the Defense Logistics 2008 Award for the Technology Implementation of the Year.
- Easy to transport and emplace via conventional carriers over land, JHSV, and other similar-sized vessels
- Emplacement requires one rigid-hull inflatable boat
- Seven personnel can deploy 120 feet of the system in approximately three hours
- Modular, folding, and pneumatically-supported structure allows space-saving packaging
- 40-foot section has the same footprint as a standard 20-foot International Shipping Organization container
- Each 40-foot section composed of four modules weighs approximately 6,500 pounds
- Each module is 10-feet long by 20-feet wide and is supported by two 5-foot diameter pneumatic floats
- Adjustable internal pressure of pneumatic tubes allows for an increased penetration onto sandy beaches to conform to existing bottom slope of the beach
- Supported by flotation tubes that are rapidly filled with minimal air pressure (about one pound-force per square inch gauge)
- Support capacity in excess of 70 tons (Military Load Class 70, main battle tank traffic)
- Requires less than 12 inches of water depth in unladen state
For more information about LCMS, please visit CHL online.
ERDC Points of Contact
Questions about LMCS?
Contact: Jimmy E. Fowler
Phone: (601) 634-3026