Embed Size (px)
Citation preview
1
…ship girder
Ocean and Naval Architectural Design
Loads & the ship girder
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
What is the most effective structure to respond to the loading on ships?
watertight strong stiff inexpensive materials inexpensive to fabricate
2
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
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.
plate
stiffeners
element supporting
stiffeners
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
Longitudinal framing systems
Midship section
3
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
Longitudinal framing systems
Midship section Deck, side shell, & bottom plating ~ all continuous longitudinal structural elements
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
Longitudinal framing systems
Midship section Longitudinal cargo bulkhead plating ~ a continuous longitudinal structural element
4
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
Longitudinal framing systems
longitudinal stiffeners, closely spaced (e.g. 600-900mm), supporting the plating
Midship section
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
Longitudinal framing systems
longitudinal stiffeners, closely spaced, supporting the plating
Midship section
5
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
Longitudinal framing systems
longitudinal stiffeners, closely spaced, supporting the plating
Midship section
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
Longitudinal framing systems
longitudinal stiffeners, closely spaced, supporting the plating
Midship section
6
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
Longitudinal framing systems
longitudinal girders Midship section
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
Longitudinal framing systems
Transverse deep web frames, (spaced @ 3-5m intervals) ~ provide transverse strength & support longitudinals in the - deck - side shell - bulkhead - bottom
Midship section
7
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
Transverse framing systems
Midship section
Continuous longitudinal structural elements ~ - main deck - 2nd deck - side shell - inner bottom (tank top) - bottom - turn of bilge
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
Transverse framing systems
Midship section
+ continuous longitudinal structural elements ~ - deck/hatch girders - centreline keel - side girder
8
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
Transverse framing systems
Midship section
Transverse frames (spaced @ 600-1000mm 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.
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
Transverse framing systems
Midship section
Brackets connect the transverse structural elements together to form a structural ring around the ship’s cross-section.
9
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
Transverse framing systems
Midship section
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.
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
Longitudinal framing systems
Midship section
Deck, side shell, bulkhead & bottom plating; deck and bottom girders; and longitudinal stiffeners ~ all continuous longitudinal structural elements contributing to resistance to longitudinal bending.
10
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
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.
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
Scantlings?
Cross sectional dimensions of a structural member.
11
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
Longitudinal - vs – transverse framing systems
Longitudinal 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.
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
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.
12
Loads Ship girder
Loads, ship girder, steel
Structural arrangements
Mixed framing systems
Midship section
References
Zubaly, R. 1996. Chapter 7: Ship Strength in Applied Naval Architecture, Society of Naval Architects & Marine Engineers.
Rawson, K.J & Tupper, E.C. Strength. 1983. Chapter 6: The Ship Girder in Basic Ship Theory, Longman Scientific & Technical.
Van Dokkum, K. 2003. Ship Knowledge, A Modern Encyclopedia, Dokmar.
Loads, ship girder, steel
Loads Ship girder
