Design Considerations for a Lightweight Modular Causeway Section (LMCS) Jimmy E. Fowler Coastal and Hydraulics Laboratory US Army Engineer Research and Development Center (601) 634-3026 Jimmy.E.Fowler@erdc.usace.army.mil

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.

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

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

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

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

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.

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

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

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

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.

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

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 0 2 4 6 8 10 12 14 10

Flat Cable Candidates *

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

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

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

1/3-scale physical model

Remained functional even with several pontoons damaged Treadway

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

QUESTIONS?

Flat Cable Candidates Tensile Strength

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

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

M4T6

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

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

Basic Tank Load Patterns: Causeway End 1 2 3 4 5 6 7 1 6

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

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

Stiffness Analysis 1 4 2 3

JHSV Class of vessel will be a Force Projection Enabler

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

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

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

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

Transitioning the shoreward end

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