Navy Lighterage Replacement Program

Transcription

1 Lightweight Composite Lighter Module Prototype Development Program Paul Coffin NSWCCD Code Macarthur Blvd West Bethesda, MD Deputy Program Manager: Dan McCluskey Naval Facilities Engineering Command, (NAVFAC) Project Manager: Himat Garala Code 6551, NSWCCD

2 The Naval Facilities Command (NAVFAC) Sealift Support Program Office is evaluating alternatives to improve the current lighterage system by Reducing platform weight Increasing load carrying capacity Increasing throughput requirements One option for achieving these goals is use lightweight composite 40 x 24 x 8 modules. This effort is investigating that option. This, and other prototypes, will be compared by at sea testing. 2

3 Program Outline Program established to rapidly design and build a prototype Establish loads Concept development Initial Design Analysis Prototype Contract Fabricate Prototype Test Prototype All this to be completed in 18 months! Activities Naval Facilities Engineering Command (NAVFAC)..Program Management Naval Surface Warfare Center, Carderock Division (NSWCCD)...Engineering Northup Grumman Ship Systems.. Prototype fabrication 3

4 Survive Sea State 5 (SS5) High deck loads Loads Definition Vehicle loads RCHT Vehicle Tire patch 31 x31 with 81 kips, equivalent to 84 psi RORO Ramp Weight of Ramp and 2 vehicles ~ 700 kips Ramp load distributed by dunnage Load assumed to be reacted by one module Load only 11 psi 4

5 Hydrodynamic Loads Sea State 5 Loads Modeled using WAMIT code (Wave Analysis, MIT). Loads depend on module assembly geometry position of hinged joints Wave height, frequency and direction 5

6 Design Ballasting requirements and damage stability necessitated internal bulkheads Many concepts considered, but schedule drove a conservative design Rough scantlings calculated based on first principals End connection attachment major challenge 24 Concepts 40 Final Design 8 6

7 Fabrication Concept If concept selected, possible purchase of large numbers of modules. Fabrication process must be adaptable to large scale production. Prismatic shapes (pultrudable, continuous lamination, ) Self aligning parts 7

8 Analysis Models built in FEMAP and analyzed in NASTRAN. Global modeling of seaway loads on worst case assemblies Longitudinal Vertical Bending Lateral Bending Torsional Bending Wave Slap: 1500 psf Vertical Bending w/ RTCH Loading Buckling Analysis Global results generated boundary conditions for detailed analysis of joints. 8

9 Analysis Longitudinal Vertical Bending with RTCH loads Max stress 24 ksi FS Buckling 2.1 Top deck y stresses x stresses Hull bottom 1st buckling mode 9

10 Analysis Lateral Bending Max stress 7 ksi 10

11 Analysis Torsional Bending Max stress 14 ksi Wave Slap Max stress 5 ksi 11

12 Detailed/Joint Analysis Loads from global analysis fed into subsection detailed analysis. 12

13 Material Testing Rapid schedule required material testing to occur after most analysis and during the prototype fabrication Northrup Grumman fabricated 24 oz. woven roving/ve panels for evaluation VARTM Vacuum bagged hand layup Hand layup Material tests (ASTM standard tests) Volume fractions Tension Compression Inplane shear ( V notched specimen) Short Beam Shear (Apparent Interlaminar Shear Strength) Bolt Bearing Tests validated material property assumptions used in the design and analysis. Specimens are being conditioned at 120F, 80% Rh, for follow on tests. 13

14 Outfitting/Deck Jewelry Module decks are populated with a diverse array of fittings Tie downs De-watering holes Hatches Lifting eyes Post Bitts Deck Jewelry placement used to assist structural attachment 14

15 Alignment Feature Modules must be joined together in up to Sea State 3 conditions. Relative motion of ends can make joining difficult. Alignment feature designed to bring ends in phase to assist joining. Feasibility demonstrated in wave tank testing at the US Naval Academy. 15

16 Prototype Fabrication Fabricated by Northup Grumman Ship Systems, Gulfport, MS. Materials: 24 oz/yd 2 E-glass woven roving/vinylester Resin, 9 and 15 lb/ft 3 balsa core. Process: Combination VARTM and hand layup. Contract Awarded October 2001 Picture taken January

17 Prototype Connector Testing Transition Load Arm End Connector Section 17

18 Contact Information Please direct any questions relating to the US Navy s Lighter systems to: Mr. Dan McCluskey Sealift Support Program Office Naval Facilities Engineering Command, (NAVFAC) Washington Navy Yard, Washington, D.C MCCLUSKEYD@NAVFAC.NAVY.MIL 18