Section 5 Bulkheads

5.1.1 These requirements cover watertight and ballast tank transverse and longitudinal bulkheads. Requirements are also given for non-watertight pillar bulkheads.

5.1.2 The requirements apply to a vertical system of stiffening on bulkheads. They may also be applied to a horizontal system of stiffening provided that equivalent end support and alignment are provided.

Table 4.5.1 Watertight and ballast tank bulkhead scantlings

Item and requirements	Watertight bulkhead	Ballast tank bulkhead
(1) Plating thickness for plane, symmetrically corrugated and double plate bulkheads	but not less than 5,5 mm	but not less than 6,5 mm
	In the case of symmetrical corrugations, s is to be taken as b or c in Figure 3.2.1 Corrugated section in Ch 3,2 whichever is the greater
(2) Modules of rolled and built stiffeners, swedges, double plate bulkheads and symmetrical corrugations
	In the case of symmetrical corrugations, s is to be taken as p, see also Note 2
(3) Inertia of rolled and built stiffeners and swedges	—
(4) Symmetrical corrugations and double plate bulkheads	Additional requirements to be complied with as detailed in Table 4.5.2 Symmetrical corrugations and double plate bulkheads (additional requirements)
(5) Stringers or webs supporting vertical or horizontal stiffening (a) Modules
(b) Inertia	—
s, S, k as defined in Table 4.3.3 Strength/weather deck plating d w = web depth of stiffening member, in mm f = but not to be taken greater than 1,0 h 4 = load head, in metres, measured vertically as follows: For watertight bulkhead plating, the distance from a point one-third of the height of the plate above its lower edge to a point 0,91 m above the bulkhead deck at side For ballast tank bulkhead plating, the distance from a point one-third of the height of the plate above its lower edge to the top of the tank, or half the distance to the top of the overflow, whichever is greater For watertight bulkhead stiffeners or girders, the distance from the middle of the effective length to a point 0,91 m above the bulkhead deck side For ballast tank bulkhead stiffeners or girders, the distance from the middle of the effective length to the top of the tank, or half the distance to the top of the overflow, whichever is the greater le = effective length of stiffening member, in metres = spacing of corrugations as shown in Ch 3, Figure 3.2.1 Corrugated section γ = 1,4 for rolled or built sections and double plate bulkheads = 1,6 for flat bars = 1,1 for symmetrical corrugations of ballast tank bulkheads = 1,0 for symmetrical corrugations of watertight bulkheads
Note 1. In no case are the scantlings of ballast tank bulkheads to be less than the requirements for watertight bulkheads. Note 2. In calculating the actual modules of symmetrical corrugations the panel width b, is not to be taken greater than that given by Pt 3, Ch 3, 2.1 Geometric properties of section Note 3. For rolled or built stiffeners with flanges of face plate, the web thickness is to be not less than whilst for flat bar stiffeners the web thickness is to be not less than than .

5.2.1 All pontoons (L ≤ 30 m) are to be subdivided by at least two transverse watertight bulkheads and one watertight longitudinal bulkhead. For pontoons where 30 m < L ≤ 65 m, at least three transverse watertight bulkheads and one longitudinal watertight bulkhead, or two transverse and two longitudinal watertight bulkheads are to be fitted.

5.2.2 The bulkheads are to be spaced at reasonably uniform intervals.

5.2.3 The watertight bulkheads are to be the full depth of the pontoon and are to provide support for the weather and vehicle deck.

5.2.4 Watertight recesses or doors in bulkheads are generally to be so framed and stiffened as to provide strength and stiffness equivalent to the requirements for watertight bulkheads.

5.2.5 Any machinery spaces inside pontoons are to be protected by watertight bulkheads.

5.3.1 The scantlings of watertight and ballast tank bulkheads are to comply with the requirements of Table 4.5.1 Watertight and ballast tank bulkhead scantlings.

5.3.2 Where bulkhead stiffeners support deck girders, transverses or pillars over, they are also to satisfy the requirements of Table 4.5.1 Watertight and ballast tank bulkhead scantlings.

5.3.3 Where watertight bulkhead stiffeners are cut in way of watertight doors in the lower part of a bulkhead, the opening is to be suitably framed and reinforced. Where stiffeners are not cut but the spacing between the stiffeners is increased on account of watertight doors, the stiffeners at the sides of the doorways are to be increased in depth and strength so that the efficiency is at least equal to that of the unpierced bulkhead, without taking the stiffness of the door frame into consideration. Watertight recesses in bulkheads are generally to be so framed and stiffened as to provide strength and stiffness equivalent to the requirements for watertight bulkheads.

Table 4.5.2 Symmetrical corrugations and double plate bulkheads (additional requirements)

Type of bulkhead	Parameter	Watertight bulkheads	Ballast tank bulkheads
Symmetrically corrugated		Not to exceed:	Not to exceed:
		at top, and	at top, and
		at bottom	at bottom
(see also Notes 1 and 2)	d	—	To be not less than 39le mm
	θ	To be less than 40°
Double plate		Not to exceed:	at top, and
			at bottom
		Not to exceed:	at top, and
			at bottom
	d	—	To be not less than 39le mm
	A w	Not to exceed:	Not to exceed:
		at top.	at top.
		and	and
		at bottom	at bottom
s, k as defined in Table 4.3.3 Strength/weather deck plating b = panel width as in Pt 3, Ch 3, 2.1 Geometric properties of section 2.1.4 d = depth, in mm, of symmetrical corrugation or double plate bulkhead le = as defined in Pt 3, Ch 3, 2.2 Determination of span point A w = shear area, in cm2 of web of double plate bulkhead θ = angle of web corrugation to plane of bulkhead
Note 1. The plating thickness at the middle of span le of corrugated or double plate bulkheads is to extend not less than 0,2le m above mid-span. Note 2. Where the span of corrugations exceeds 15 m, a diaphragm plate is to be arranged at about mid-span.

5.4.1 Where corrugated and double plated bulkheads are fitted in pontoons the additional requirements of Table 4.5.2 Symmetrical corrugations and double plate bulkheads (additional requirements) are to be met.

5.5.1 The scantlings of non-watertight pillar bulkheads are to comply with the requirements of Table 4.5.3 Non-watertight pillar bulkhead.

Table 4.5.3 Non-watertight pillar bulkhead

Parameter	Requirement
(1) Minimum thickness of bulkhead plating	5,5 mm
(2) Maximum stiffener spacing	1500 mm
(3) Minimum depth of stiffeners or corrugations	100 mm
(4) Cross-section area (including plating) for rolled, built or swedged stiffeners supporting beams, longitudinals, girders or transverse	(a) Where	A = A 1
	(b) Where	A = A 2
	(c) Where
	A is obtained by interpolation between A 1 and A 2
(5) Cross -sectional area (including plating) for symmetrical corrugations	(a) Where	A = A 1
	(b) Where	A = A 2
d w, t p, b, c as defined in Pt 3, Ch 3, 2 Structural idealization for pontoons r = radius of gyration, in mm of stiffener and attached plating = for rolled built or swedged stiffeners = for symmetrical corrugation = moment of interia, in cm4, of stiffener and attached plating s = spacing of stiffeners, in mm A = cross-sectional area, in cm2, of stiffener and attached plating A 1 = = As a first approximation A 1 may be taken as A 2 = = As a first approximation A 2 may be taken as = P, le as defined in Table 4.5.4 Pillars λ =

5.6.1 Pontoon tanks used for the storage of flammable liquid are to have at least a one tank or dry space separation from the ship interface.

Table 4.5.4 Pillars

Parameter	Requirement
(1) Cross-sectional area of all types of pillar	See note
(2) Minimum wall thickness of tubular pillars	The greatest of the following: (a) = (b) = (c) =
(3) Minimum wall thickness of hollow rectangular pillars or web plate thickness of or channel sections	The lesser of the following: (a) = (b) = = but not less than
(4) Minimum thickness of flanges of angle or channel sections	The lesser of the following: (a) = (b) =
(5) Minimum thickness of flanges of built or rolled sections	The lesser of the following: (a) = (b) =
b = breadth of side of a hollow rectangular pillar or breadth of flange or web of a built or rolled section, in mm d p = mean diameter of tubular pillars, in mm k = material factor l = overall length of pillar in metres le = effective length of pillar in metres lp = distance, in metres, between centres of the two adjacent spans of girder, or transverse, supported by the pillar P a = load, in kN, from pillar or pillars above (zero if no pillars over) r = least radius of gyration of a pillar cross-section, in mm, and may be taken as r = A p = cross-sectional area of pillar, in cm2 S = as defined in Table 4.3.3 Strength/weather deck plating H g = is defined as the equivalent sea water head from disturbed design loads including, vehicles, passengers, ramp loads or ship's ramp load or any combination of these, but is not to be taken less than 0,01L + 0,7m = least moment of interia of cross-section, in cm4 P = load, in kN, supported by the pillar and is to be taken as 10,06 S H g lp + P a but not less than 19,62 kN = For pillars loaded by concentrated loads from ramps or other structures above P, is to be individualy calculated, in kN, for the loads involved including distributed loads
Note As a first approximation A p may be taken as and the radius of gyration estimated for a suitable section having this area. If the area calculated using this radius of gyration differs by more than 10 per cent from the first approximation, a further calculation using the radius gyration corresponding to the mean area of the first and second approximation is to be made.