ContentsKEEL2Single Bottom Structure2Pillars6Spacing of the pillars6Construction6Ship Building Quality Steel9The Composition9Special Shipbuilding steels9Heat Treatment of Carbon Steel9Aluminum Alloy10Al Alloy Tests10Classes, Rules and Regulations and IACS13Rules and regulations of the Classes13

The main ship structural assemblies are:1. Bottom structure2. Side structure3. Deck structure4. BulkheadsBottom StructureKEEL

is located at the center line of the bottom structure and are the backbone of the ship.Contributes substantially to the longitudinal strength and distributes local loading caused by docking.Commonest form is flat plate keel which is fitted in ocean-going vessels.Bar keel is used in small vessels (e.g. trawlers, tugs).When double is fitted, flat plate type is always used.Duck keel is provided in some double bottoms of some vessel. It carries the double-bottom piping.Single Bottom StructureIn smaller vessel having single bottom, the vertical plate floors are fitted at every frame space and are stiffened at their upper edge.A centerline girder is fitted and one side girder is fitted each of the center line when beam is less than 10m.When the beam is larger, two side girders may be fitted and additional continuous or intercostal girders, which are stiffened at their upper edge may also be fitted.A wood ceiling may be fitted across the floors but this does not constitute an inner bottom offering any protection if the outer bottom is damaged.

Double BottomThe double bottom is composed of outer and inner watertight bottom plating to provide complete watertight integrity should the outer shell plating be damagedThe double bottom space is utilized to carry oil fuel and fresh water as well as providing the required ballast capacity.The minimum depth of the double bottom depends on the size of the vessel and is determined by the rule requirements of classification societies.The actual depth is sometimes increased in places to provide adequate capacity of the double-bottom tanks. The increase in the inner bottom height is always made by a gradual taper in the longitudinal directionto avoid sudden discontinuities in the structure.One or two side girders, which could be either continuous or intercostal, are fitted port and starboard depending on the width of the ship.Intercostal girders or side girders, and plate floors will have lightening holes at regular intervals to reduce the structural weight, and will have manholes to provide access.Transversely Framed Double BottomThis is used in ships of length less than 120 metersIs made up of vertical floors which may be watertight, solid or of bracket construction.Flat plate keels are used in these structures.

BulkheadsVertical partition in a ship arranged transversely or fore and aft are referred to as bulkheads.FunctionThey are of greatest importance are the min hull transverse and longitudinal bulkheads, diving the ship into a number of watertight compartments and supporting the external and structural transverse loading.They provide support for deck and bottom girders and longitudinal, resisting any tendency for transverse deformation of the ship.The main hull bulkheads of sufficient strength are made watertight in order that they may contain any flooding in the event of a compartment on one side of the bulkhead being bilged or breached.Bulkheads are effective for containing fires.Spacing(location) of watertight bulkheads orFor cargo ship, a collision bulkhead (in forward), an aft peak bulkhead and watertight bulkheads must be fitted at each end of the machinery space. The minimum number of transverse bulkheads is three when the ship has an aftengine room and four when the engine room is not at the aft end.For collision bulkhead, a heavy bulkhead is specified and located so that it is not so far forward as to be damaged on impact. (minimum distance is 10m form fore end)The aft peak bulkhead is intended to enclose the stern tubes in a watertight compartment, preventing any emergency form leakage where the propeller shafts pierce the hull.Machinery bulkheads provide a self-contained compartment for boiler and engines, preventing damage to these vital components of the ship by flooding in an adjacent hold.Each of the main bulkhead may extend to the uppermost continuous deck.The strength of the transverse watertight bulkheads is maintained to the strength deck, which may be above the freeboard deck.For Bulk carriers, reduced freeboard necessitates further consideration into the spacing of the watertight bulkheads.Construction of bulkheadTwo types exist: plain and corrugatedPlain type: the plating of a flat transverse bulkhead is generally welded in horizontal strakes with the thickness increases with depth.Vertical stiffening is provided in the form of welded inverted angle bars or OB.The stiffeners may be supported by horizontal stringers to reduce in the scantling as a result of reduce span.The boundaries are double continuously filled welded directly to the shell decks and tank top.

PillarsFunctionThe primary function is to carry the load of the decks and weights upon the decks vertically down to the ships bottom structure where these loads are supported by the upward buoyant forces. Pillars in cargo holds fulfill the function and are in compression without bracket connections at their ends.The second one is to tie together the structure in a vertical direction. Pillars in the machinery spaces serve this function and are heavily bracketed at their ends to permit tensile loadings.Hold pillars may be used as main structural elements to reduce the scantling of the deck transverses and deck girders by reducing the effective spans of these heavy structural members.Spacing of the pillarsSince pillars in holds will interfere with the stowage arrangements, widely spaced pillars of large section are used.Common arrangement is two-row system, with pillars at the hatch corners mid-length of hatch supporting deck girders adjacent to the hatch sides.As the deck girder size is to some extent dependent on the supported span, where only a mid-hatch length pillar is fitted the girder scantlings will greater than that where two hatch corner pillars are fitted.Pillars can be eliminated if a clear space is to be provided, but the deck girder will be larger and may be supported by webs at the bulkhead.Construction Hold pillars are primarily subjected to compressionIdeal section is the tubular. Hollow rectangular and octagonal sections are also used.Pillars have a bearing fit and it is important that the loads at the head and heel of the pillar should be well distributed.

Deep Tank

Ship Building Quality SteelThe following steels are predominantly used in shipbuilding Rolled plain steel (for plates and profiles , foundation, etc.) Rolled special steel (high-tensile steel, low-temperature steel for LNG tanker, corrosion resistance for product tanker, non-magnetic steel for compass area) Cast steel (rudder, stern, stem) Forged steel (for anchors, chains, etc.)IACS graded the steels into five different qualities (Grade A, B, C, D, E) with Grade A being an ordinary mild steel to LR requirement. Grade B is better quality and used when thicker plates are required in the more critical regions. Grade C, D, E possess increasing notch-tough characteristics, with Grade C being ABS requirements.Grades A,B,D,DS,CS, and E are most extensively used.The CompositionThe microstructure of shipbuilding steels consists of iron-carbide(cementite) dispersed in a matrix of ferrite.Steel for hull structure is mild steel(0.15%-.23%C) with high Mn content. Both S and P are kept to a minimum (