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

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Presentation on theme: "Design Considerations for a Lightweight Modular Causeway Section (LMCS) Jimmy E. Fowler Coastal and Hydraulics Laboratory US Army Engineer Research and."— Presentation transcript:

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

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

4 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 Desired LMCS Features

5 Primary Design Considerations ParameterLMCSMCS 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 ft90 tons per 80 ft Transportability JHSVStrategic 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 LMCS is expected to save 70% in weight and volume compared to existing MCS Causeway while retaining 100% of MCS payload capacity. Volume and Weight

8 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 Transportability 36 tons – CH-53E Super Stallion Helicopter 9ft 20ft 10ft

9 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 Deployability and Recoverability

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

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

13 Asymptotic to Zero Asymptotic to Archimedes Depth Value for Current Design  = 3.76E+10 lb-in^2 10 Negative Deflection, inches Structural Stiffness

14 Flat Cable Candidates *

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

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

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

18 1/3-scale physical model

19 Remained functional even with several pontoons damaged Treadway

20 MCS VS LMCS Space & Weight Supporting equipment required Number of personnel required for assembly Assembly time LMCS MCS

21 QUESTIONS?

22 Flat Cable Candidates Tensile Strength

23 Risk Mitigation 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 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 Operational Requirements

25

26 M4T6

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

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

29 Basic Tank Load Patterns: Causeway End

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

32 Stiffness Analysis

33 JHSV Class of vessel will be a Force Projection Enabler

34 - 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 JRAC Joint Rapid Airfield Construction RPE Rapid Port Enhancement PROBLEM : *Lack of Infrastructure *Anti-access JRAC Objectives - Increase airfield MOG capacity Increase airfield location options Decrease engineering timelines and logistical requirements 6.2 STO 6.3 STO Enable Theater Access

35 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 Designs Evaluated

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

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

38 Transitioning the shoreward end

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


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