Section 6 Fore peak structure

6.1.1 The requirements given in this Section apply to the arrangement of primary structure supporting the peak side framing and bulbous bow, the arrangement and scantlings of wash bulkheads and perforated flats, and the scantlings of collision bulkheads.

6.1.2 In ships of very full form it is recommended that transverse framing and side transverses supporting longitudinal framing, together with attached floors and beams, be inclined at an angle to the centreline of ship so that the frames or transverses lie as near normal to the shell plating as possible.

6.2.1 The bottom of the peak space is generally to be transversely framed with arrangements and scantlings as detailed in Pt 3, Ch 5, 5.2 Single bottoms − Transverse framing 5.2.1. Longitudinally framed bottom structure will be specially considered.

6.3.1 Above the floors, transverse side framing is to be supported by one of the following arrangements:

1. Side stringers spaced about 2,0 m apart and supported by struts fitted at alternate frames. The struts are to be bracketed to the frames and where the span is long, supported at the centreline by a complete or partial wash bulkhead or equally effective structure. Intermediate frames are to be bracketed to the stringer plates.

2. Side stringers spaced about 2,0 m apart and supported by web frames. The upper ends of the web frames are to be supported under the tank top by suitable deep beams or buttresses which should generally form a ring structure.

3. Perforated flats spaced not more than 2,5 m apart. The area of perforations in each flat is to be not less than 10 per cent of the total area of the flat. The plating is to be suitably framed in way of openings.

4. A combination of the above arrangements.

6.3.2 Where the depth of the peak space exceeds 10 m, a perforated flat is to be arranged at about mid-depth.

6.3.3 Where the length of the space exceeds 10 m and the side framing is supported as required by Pt 3, Ch 5, 6.3 Side structure − Transverse framing 6.3.1 or Pt 3, Ch 5, 6.3 Side structure − Transverse framing 6.3.1.(c), additional transverse strengthening in the form of transverse wash bulkheads or web frames is to be provided.

6.3.4 The scantlings of side stringers supported by struts, and also of the struts and their brackets, are to be determined from Table 5.6.1 Fore peak structure.

Table 5.6.1 Fore peak structure

Item	Parameter	Requirement
(1) Unflanged stringers supported by panting beams at alternate frames	Web thickness	mm
	Web depth	mm
(2) Struts	Cross-sectional area	cm2
	Least inertia	cm4
(3) Brackets supporting stringers and beams	Thickness	mm
	Arm length	mm in way of struts mm at intermediate frames
(4) Perforated flats and wash bulkheads (excluding lowest strake of plating) see Notes 1, 2 and 3	Plating thickness	mm
	Stiffener modulus	cm3
(5) Diaphragms in bulbous bows and lowest strake of wash bulkhead	Plating thickness	mm
Symbols
L, B, S, s, k = as defined in Pt 3, Ch 5, 1.4 Symbols and definitions 1.4.1 b = 1,4 for rolled or built sections = 1,6 for flat bars h 5 = vertical distance, in metres, from the stringer to a position 3 m above the deck height obtained from Pt 3, Ch 1, 6.1 Principal particulars 6.1.11 h 6 = vertical distance, in metres, from mid-depth of tank to top of tank e = effective length of stiffening member, in metres, see Table 1.9.1 Watertight and deep tank bulkhead scantlings and Table 1.9.3 Bulkhead end constraint factors in Pt 4, Ch 1 s 1 = spacing of peak frames, in mm, but to be taken not less than 600 mm s 2 = spacing of stiffeners, in mm, but to be taken not less than 800 mm B 1 = B, but need not be taken greater than 32 m L 2 = L, but need not be taken greater than 215 m S 1 = vertical spacing or mean spacing of stringers, in metres S 2 = horizontal spacing of struts, in metres
Note 1. For oil tankers, see also Pt 4, Ch 9, 10.7 Application of stiffening requirements Note 2. For horizontal flats supporting vertical webs in the fore peak tank, the thickness of the flat in way of the web is to comply with Table 9.7.1 Transverse oiltight bulkhead scantlings. Note 3. For minimum thickness within fore peak tanks of oil tankers, see also Pt 4, Ch 9, 10.2 Compartment minimum thickness.

6.3.5 The scantlings of side stringers supported by web frames, and also of the web frames, are to be determined from Pt 3, Ch 5, 4.5 Primary structure at sides.

6.3.6 The scantlings of perforated flats are to be determined from Table 5.6.1 Fore peak structure.

6.4.1 The spacing and scantlings of side transverses supporting longitudinal framing are to be as required by Pt 3, Ch 5, 4.5 Primary structure at sides.

6.4.2 Where the depth of a tank exceeds 10 m, side transverses are generally to be supported by one or more perforated flats or an arrangement of struts.

6.4.3 Suitable transverses or deep beams are to be arranged at the top of the tank and at perforated flats to provide end rigidity to the side transverses.

6.5.1 Where a bulbous bow is fitted, the structural arrangements are to be such that the bulb is adequately supported and integrated into the fore peak structure.

6.5.2 At the fore end of the bulb the structure is generally to be supported by horizontal diaphragm plates spaced about 1,0 m apart in conjunction with a deep centreline web.

6.5.3 In general, vertical transverse diaphragm plates are to be arranged in way of the transition from the peak framing to the bulb framing.

6.5.4 In way of a wide bulb, additional strengthening in the form of a centreline wash bulkhead is generally to be fitted.

6.5.5 In way of a long bulb, additional strengthening in the form of transverse wash bulkheads or substantial web frames spaced about five frame spaces apart are generally to be fitted.

6.5.6 The shell plating is to be increased in thickness at the fore end of the bulb and in other areas likely to be damaged by the anchors and chain cables. The increased plate thickness is to be the same as that required for plated stems by Pt 3, Ch 5, 3.3 Stem 3.3.2.

6.6.1 Where a fore peak space is used as a tank and the breadth of the tank at its widest point exceeds 0,5B, a complete or partial centreline wash bulkhead is to be fitted.

6.6.2 Wash bulkheads are to have an area of perforations not less than five per cent nor more than 10 per cent of the area of the bulkhead. The plating is to be suitably stiffened in way of openings.

6.6.3 The scantlings of wash bulkheads are to be determined from Table 5.6.1 Fore peak structure. Stiffeners are to be bracketed at top and bottom.

6.7.1 The position and height of the collision bulkhead are to be in accordance with the requirements of Pt 3, Ch 3, 4 Bulkhead requirements.

6.7.2 The scantlings are to comply with the requirements of Pt 4, Ch 1, 9 Bulkheads except that the thickness of plating and modulus of stiffeners are to be not less than 12 per cent greater and 25 per cent greater, respectively, than would be required for a dry space. If the collision bulkhead forms the boundary of a cargo tank or cofferdam in an oil tanker or ore carrier the minimum thickness requirements of Pt 4, Ch 9, 10 Construction details and minimum thickness are also to be complied with.

6.7.3 Doors, manholes, permanent access openings or ventilation ducts are not to be cut in the collision bulkhead below the freeboard deck, see also Pt 5, Ch 13, 3 Drainage of compartments, other than machinery spaces. The number of openings in collision bulkheads above the freeboard deck is to be kept to a minimum compatible with the design and proper working of the ship. All such openings are to be fitted with means of closing to weathertight standards.