1. Design Considerations for a Lightweight Modular Causeway Section (LMCS)
Jimmy E. Fowler
Coastal and Hydraulics Laboratory
US Army Engineer Research and Development Center
(601)

2. JHSV  Force Projection Enabler
Needs causeway systems for austere SPODs
This is a similar venture by the Marine Corps to test High Speed Sealift for intratheater movements of forces and equipment.
This particular vessel is the HSV Swift and was recently used in our JLOTS ’03 exercise to move NEW HORIZON exercise equipment from Honduras to Guatemala.

3. Existing Causeway Systems
--- NLS, MCS, INLS ---
all steel barge construction
Not JHSV
transportable
or deployable

4. Desired LMCS Features
Transportable by and rapidly deployable from TSV/JHSV
Minimal storage/shipping volume
Tailorable to desired gap length
M1A2 payload
No in-water connections
Transportable by primary mover and air lift
Interface with existing JLOTS watercraft
Operational capabilities
- Sheltered ports and harbors
- Sea-state operations

5. Primary Design Considerations
Parameter
LMCS
MCS
Payload
M1A2 Main Battle Tank
Volume
20 x 9 x 10 for 60 ft
2400 cu ft per 80 ft
(40 x 8 x 9) x 3 for 80 ft
8640 cu ft per 80 ft
Weight
28 tons per 80 ft
90 tons per 80 ft
Transportability
JHSV
Strategic Sealift Ship
Deployability
No in water connections
Numerous in water connections
Survivability
SS 5

6. TWO “NEW” CONCEPTS High-strength fiber connections: foldable
maintains stiffness under tension
adjustable compliancy
Inflatable buoyancy
reduces internal structure in deck
minimizes storage volume
adjusts to sloping bottom

7. Volume and Weight
LMCS is expected to save 70% in weight and volume compared to existing MCS Causeway while retaining 100% of MCS payload capacity.

8. Transportability
36 tons – CH-53E Super Stallion Helicopter
Weight of system  Air delivery may be limiting factor
Volume  Stored and shipped configuration – less is best
ISO compatibility - MHE & Existing Military Prime Mover transportable
10ft
20ft
9ft

9. Deployability and Recoverability
TSV & JHSV on-board crane limitations
Weight and size
Equipment Requirements
Large Rigid Hull Inflatable Boat (RHIB)
Shore-based winch
Safety considerations
No in-water connections
Minimize assembly time
Minimize number of personnel
Simplify mooring system

10. Primary Deployment Option
Unstiffened Units
Draw units together
and stiffen section
(see details)
JHSV
Deployment
Boat or
shore winch or anchor
Lightweight deployment Ramp w/
floating support
Continuous feed from rear of JHSV off ramp or rail system

11. Initially loosely connected by high strength straps/cables
On board winch pulls sections together and sets design tension.
Overall stiffness is combination of joint stiffness and module stiffness.

12. Survivability Floatation Resistance to puncture/abrasion
- Contact with sea/river bed
- Redundancy (2nd internal tube)
- Small punctures  Slow pressure loss
Flat cable (strap) service life
- Material properties
Adjustable stiffness/compliance

13. Structural Stiffness Negative Deflection, inches 0 2 4 6 8 10 12 14
Asymptotic to Zero
Negative Deflection, inches
Value for Current Design
EI = 3.76E+10 lb-in^2
Asymptotic
to Archimedes Depth 10

14. Flat Cable Candidates *

15. Effect of Cable Stiffness and Length
Relative Shapes
60 Ft Cable
10 Ft Cables
Solid

16. Floats Removed: 3
Even with 3 floats removed, positive freeboard is maintained

17. Structural Stiffness Stiffness is a function of strap properties
Full Scale Design All plate thicknesses except Main Beams = ¼ “
Main Beams: Plate Thickness = 1/2”
Internal
Stiffeners
Stiffness
is a function
of strap
properties
End Plate
End Plate
Side Plate
Bottom Plate
Strap/Cable Conduits

18. 1/3-scale physical model

19. Remained functional even with several pontoons damaged
Treadway

20. MCS LMCS MCS VS LMCS Assembly time
Number of personnel required for assembly
Supporting equipment required
Identify major accomplishments through the month prior to the IPR for the overall research area. The accomplishments should reflect significant and meaningful scientific contributions or technological achievements rather than just indicating milestones met.
Include accomplishments for all years with emphasis on previous 12 months.
Accomplishments must be specific and must be mapped to milestones and products provided in P2.
Illustrate findings through graphics, tables, charts, photography, equations, etc. Verbally describe significance of findings.
Provide expected accomplishments through the end of the current FY.
Place the accomplishments provided herein, in narrative form in P2.
Space & Weight

21. QUESTIONS?

22. Flat Cable Candidates
Tensile Strength

23. Risk Mitigation 1 2 3 4
Small punctures result in “slow” loss of pressure/buoyancy
Severe damage results in instantaneous loss of floatation but with current design:
Minimum freeboard is still positive for up to 4 adjacent tube failures
Will include redundancy – extra air bladder for each tube
Relatively simple to replace damaged sections

24. Operational Requirements
Vehicle speed
Number of vehicles on causeway
- Weight and speed
 Entire causeway system
 Per stiffened section
- Clearance between vehicles
Maximum lane width relative to causeway section width
- M1A1 / M1A2 Abrams is 12 ft. wide
Ramp and causeway interface
- Surface deck deflection
- Ramp configurations

26. M4T6

27. Alternate Float Geometry Options
10-ft
10-ft
1.5-ft
1-ft
1.5-ft
1-ft
5-ft
6-ft
5-ft
6-ft
10-ft
10-ft
1.5-ft
1-ft
1.5-ft
1-ft
7-ft
8-ft
7-ft
8-ft
Alternate Float Geometry Options

28. End View
Proposed method for storing/transporting
Straps are pre-threaded
Yields 60-ft per package
10.0 ft
9.0 ft

29. Basic Tank Load Patterns: Causeway End1 2 3 4 5 6 7 1 6

30. LMCS Buoyancy & Stability Tests
Weights were added in precise locations to simulate M1A2
Roll characteristics were evaluated by off-setting weights

31. Historical Perspective
2 companies used to construct 300 ft
Labor intensive
Vulnerable to puncture

32. Stiffness Analysis 1 4 2 3

33. JHSV Class of vessel will be a Force Projection Enabler

34. Lack of Infrastructure Joint Rapid Airfield Construction
Enable Theater Access
Lack of Infrastructure
PROBLEM:
Anti-access
JRAC
Joint Rapid Airfield Construction
RPE Rapid Port Enhancement
JRAC Objectives -
Increase airfield MOG capacity
Increase airfield location options
Decrease engineering timelines and logistical requirements
6.2 STO
RPE Objectives -
Maximize JHSV Utility
Increase number of Potential Port Sites
Increase number of Lanes Per Site
Decrease Cube/Weight and Times Per
Deployment of Systems
6.3 STO

35. Designs Evaluated All Steel or Composite No volume reduction Too heavy
Bottom Founded with Hydrobeams
Large fabric bags (20ft diameter)
Hydraulic pumps – time to fill
Not easily moved/positioned
Currents/mooring problems
Floating using Hydrobeams/Airbeams

36. Causeway Section (LMCS)
Proposed method for storing/transporting
Straps are pre-threaded
Yields 60-ft per package
3.5 tons per 10 ft module
Lightweight Modular
Causeway Section (LMCS)
Initial Concept
10ft
20ft
9ft

37. On board air cannisters for inflation
Module Side View With Upper & Lower Straps and Shear Connectors and tensioning/positioning straps
10-ft
18-in
6-ft
5-ft
On board air cannisters for inflation

38. Transitioning the shoreward end

39. Structural Stiffness Stiffened section length relative to total length
Strap characteristics
Breaking strength
Elasticity considerations
Shear/torsion rods