Section 5 Deck structure

5.1.1 Where the deck, outside the line of openings, is longitudinally framed in the midship region, this system of framing is to be carried as far forward and aft as possible.

5.2.1 The scantlings of deck beams and longitudinals are to comply with the requirements of Table 5.5.1 Deck beams and longitudinals forward and aft.

Table 5.5.1 Deck beams and longitudinals forward and aft

Location	Modulus, in cm3	Inertia, in cm4
(1) Transverse beams	Z = 4,3 × k × s × h 1 × le 2 + 1,5 + 0,05L	-
(2) Longitudinals	Z = 4,3 × k × s × h 1 × l e 2 + 1,5 + 0,05L	-
(3) In way of the crown of a tank	Z = as required in Pt 3, Ch 7 Bulkheads
Symbols
L, s, Z and I are as defined in Pt 3, Ch 5, 1.4 Symbols and definitions 1.4.1 le = as defined in Pt 3, Ch 5, 1.4 Symbols and definitions 1.4.1 but to be taken as not less than 2 m h1 = head, in metres, as defined in Pt 3, Ch 3, 4 Design loading k = higher tensile steel factor, see Pt 3, Ch 2, 1.3 Steel 1.3.3
Note The web depth of beams is to be not less than 45 mm.

5.2.2 End connections of longitudinals to bulkheads are to provide adequate fixity, lateral support and so far as necessary, direct continuity of longitudinal strength.

5.2.3 End connections of beams are to be in accordance with the requirements of Pt 3, Ch 10, 3 Secondary member end connections.

5.3.1 Girders and transverses supporting beams and deck longitudinals in the fore ship and aft ship regions, are to comply with the requirements of Table 5.5.2 Deck supporting structure fore and aft. In general, transverses, webs or frames of increased scantlings, see Pt 3, Ch 5, 4.4 Web frames and side transverses, are to be arranged in way of deck transverses and are to be in line with the floors, where practicable.

Table 5.5.2 Deck supporting structure fore and aft

Item	Parameter	Requirement
Girders and transverses in dry spaces, see Note	Modulus	Z = 4,75 x k x h 1 x S x le 2 cm3
	Inertia
Pillars in dry spaces, see Note	Cross-sectional area of all types of pillar	cm4
	Minimum wall thickness of hollow pillars	The greater of (a) and (b):
		(a)	t = 0,033d p for tubular pillars, mm
		(b)	t = 0,056b for square pillars, mm
		(c)	t = 5 mm
Symbols
S, Z, I and t are as defined in Pt 3, Ch 5, 1.4 Symbols and definitions 1.4.1 b = breadth of side of a hollow rectangular pillar, in mm dp = mean diameter of tubular pillars, in mm h1 = head, in metres, as defined in Pt 3, Ch 3, 4 Design loading l = overall length of pillar, in m le = as defined in Pt 3, Ch 5, 1.4 Symbols and definitions 1.4.1, but not less than 2 m r = least radius of gyration of pillar cross-section, in mm, and may be taken as: r = Ap = cross-sectional area of pillar, in cm2 Ip = least moment of inertia of cross-section, in cm4 P = load supported by the pillar, in tonne-f k = higher tensile steel factor, see Pt 3, Ch 2, 1.3 Steel 1.3.3
Note For deck supporting structure in tanks, see also Pt 3, Ch 7 Bulkheads.

5.3.2 Transverses supporting deck longitudinals are to be spaced not more than 3,5 m apart.

5.3.3 The web thickness, stiffening arrangements and end connections of primary supporting members are to be in accordance with Pt 3, Ch 10, 4 Construction details for primary members.

5.3.4 Where a girder or transverse is subjected to concentrated loads, such as pillars or winch seatings, the scantlings are to be determined by direct calculation.

5.3.5 Pillars are to comply with the requirements of Table 5.5.2 Deck supporting structure fore and aft.

5.3.6 Pillars are to be fitted in the same vertical line wherever possible, and are to be attached at their heads by efficient brackets, in order to transmit the load effectively. Doubling plates are generally to be fitted under the heels of pillars. The pillars are to have a bearing fit.

5.3.7 The structure in single or double bottoms in way of pillars is to be suitable to support the load imposed on this structure by the pillars.

5.3.8 Where bulkhead stiffeners support pillars, girders or transverses, the stiffeners, in association with a width of plating equal to half the stiffener spacing, should comply with the requirements of Table 5.5.2 Deck supporting structure fore and aft for pillars.