Design considerations for a lightweight modular causeway section lmcs
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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 Development Center (601) 634-3026 [email protected] JHSV  Force Projection Enabler

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Design Considerations for a Lightweight Modular Causeway Section (LMCS)

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Design considerations for a lightweight modular causeway section lmcs

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

[email protected]


Design considerations for a lightweight modular causeway section lmcs

JHSV  Force Projection Enabler

Needs causeway systems for austere SPODs


Existing causeway systems

Existing Causeway Systems

--- NLS, MCS, INLS ---

all steel barge construction

Not JHSV

transportable

or deployable


Design considerations for a lightweight modular causeway section lmcs

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

Primary Design Considerations


Design considerations for a lightweight modular causeway section lmcs

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


Design considerations for a lightweight modular causeway section lmcs

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

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

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

JHSV

Primary Deployment Option

Deploy

Unstiffened Units

Draw units together

and stiffen section

(see details)

  • Continuous feed from rear of JHSV off ramp or rail system

Deployment

Boat or

shore winch or anchor

Lightweight deployment Ramp w/

floating support


Design considerations for a lightweight modular causeway section lmcs

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.


Design considerations for a lightweight modular causeway section lmcs

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


  • Design considerations for a lightweight modular causeway section lmcs

    Structural Stiffness

    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

    Flat Cable Candidates

    *


    Relative shapes

    Effect of Cable Stiffness and Length

    Relative Shapes

    60 Ft Cable

    10 Ft Cables

    Solid


    Floats removed 3

    Floats Removed: 3

    Even with 3 floats removed, positive freeboard is maintained


    Structural stiffness

    Structural Stiffness

    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


    Design considerations for a lightweight modular causeway section lmcs

    1/3-scale physical model


    Design considerations for a lightweight modular causeway section lmcs

    Remained functional even with several pontoons damaged

    Treadway


    Design considerations for a lightweight modular causeway section lmcs

    MCS VS LMCS

    MCS

    LMCS

    Assembly time

    Number of personnel required for assembly

    Supporting equipment required

    Space & Weight


    Design considerations for a lightweight modular causeway section lmcs

    • QUESTIONS?


    Structural stiffness1

    Structural Stiffness

    • Stiffened section length relative to total length

      • Strap characteristics

      • Breaking strength

      • Elasticity considerations

      • Shear/torsion rods


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