Ocean and Naval Architectural Design

Transcription

1 Ocean and Naval Architectural Design & the ship girder ship girder, ship girder, steel What is the most effective structure to respond to the loading on ships? watertight strong stiff inexpensive materials inexpensive to fabricate 1

2 , ship girder, steel Stiffened panels Consider hydrostatic pressure on the shell of a ship. (or on the bulkhead of a cargo tank). The normal pressure loads can be effectively resisted by a stiffened plate, or panel. element supporting stiffeners plate stiffeners, ship girder, steel 2

3 , ship girder, steel Deck, side shell, & bottom plating ~ all continuous longitudinal structural elements, ship girder, steel Longitudinal cargo bulkhead plating ~ a continuous longitudinal structural element 3

4 , ship girder, steel longitudinal stiffeners, closely spaced (e.g mm), supporting the plating, ship girder, steel longitudinal stiffeners, closely spaced, supporting the plating 4

5 , ship girder, steel longitudinal stiffeners, closely spaced, supporting the plating, ship girder, steel longitudinal stiffeners, closely spaced, supporting the plating 5

6 , ship girder, steel longitudinal girders, ship girder, steel Transverse deep web frames, 3-5m intervals) ~ provide transverse strength & support longitudinals in the - deck - side shell - bulkhead - bottom 6

7 , ship girder, steel Transverse framing systems Continuous longitudinal structural elements ~ - main deck - 2 nd deck - side shell - inner bottom (tank top) - bottom - turn of bilge, ship girder, steel Transverse framing systems + continuous longitudinal structural elements ~ - deck/hatch girders - centreline keel - side girder 7

8 , ship girder, steel Transverse framing systems Transverse frames mm intervals) ~ provide transverse strength (not longitudinal). ~ deck frames are supported by deck girders & side shell ~ side frames are supported by deck plating, side plating, inner bottom., ship girder, steel Transverse framing systems Brackets connect the transverse structural elements together to form a structural ring around the ship s cross-section. 8

9 , ship girder, steel Transverse framing systems Longitudinal strength of transversely framed ships: ~ contributions from deck, side shell, tank top and bottom plating; hatch/deck girders and bottom girders; not from local panel stiffeners., ship girder, steel Deck, side shell, bulkhead & bottom plating; deck and bottom girders; and longitudinal stiffeners ~ all continuous longitudinal structural elements contributing to resistance to longitudinal bending. 9

10 , ship girder, steel Longitudinal - vs transverse framing systems Longitudinal stiffeners contribute to the longitudinal hull girder strength. This makes longitudinal framing more efficient than the alternative transverse framing system less structural weight required, more cargo carrying capacity. Longitudinally framed panels, e.g. on the main deck and bottom, that are subjected to compression loads, resist buckling better than transversely stiffened panels. Also, the scantlings can be changed with depth (pressure) to improve the local structural efficiency., ship girder, steel Scantlings? Cross sectional dimensions of a structural member. 10

11 , ship girder, steel Longitudinal - vs transverse framing systems require deep transverse webs for support. These web frames interfere with the arrangement of spaces inside the ship. This is inconvenient for some ship types, although not for tankers & bulkers, which is where longitudinal framing is most commonly used., ship girder, steel Mixed framing systems In practice, longitudinal and transverse framing systems can be combined. Longitudinal stiffeners are used in the bottom and deck, where their contribution to resisting longitudinal bending (and buckling) is most useful and transverse framing is used at the side to avoid obstructing interior spaces with the deep webs associated with longitudinal frames. 11

12 , ship girder, steel Mixed framing systems, ship girder, steel References Zubaly, R Chapter 7: Ship Strength in Applied Naval Architecture, Society of Naval Architects & Marine Engineers. Rawson, K.J & Tupper, E.C. Strength Chapter 6: The Ship Girder in Basic Ship Theory, Longman Scientific & Technical. Van Dokkum, K Ship Knowledge, A Modern Encyclopedia, Dokmar. 12