Clasification Society Rulefinder 2016 - Version 9.25
Clasification Society Rules and Regulations - Rules and Regulations for the Classification of Offshore Units, January 2016 - Part 4 STEEL UNIT STRUCTURES - Chapter 6 Local Strength - Section 9 Superstructures and deckhouses |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
![]() Section 9 Superstructures and deckhouses9.1 General9.1.1 The term ‘erection’ is used in this Section to include both superstructures and deckhouses. 9.1.2 Erections are to comply with
Units with a Rule length, L, greater than 150 m will be specially considered. 9.1.3 The scantlings of exposed bulkheads and decks of deckhouses are generally to comply with the requirements of this Section, but increased scantlings may be required where the structure is subjected to local loadings greater than those defined in the Rules, see also Pt 4, Ch 6, 9.1 General 9.1.6. Where there is no access from inside the house to below the freeboard deck or into buoyant spaces included in stability calculations, or where a bulkhead is in a particularly sheltered location, the scantlings may be specially considered. 9.1.4 The scantlings of superstructures which form an extension of the side shell or which form an integral part of the unit’s hull and contribute to the overall strength of the unit will be specially considered. The upper hull structure of column-stabilised units are to comply with Pt 4, Ch 6, 3 Watertight shell boundaries. 9.1.5 Any exposed part of an erection which may be subject to immersion in damage stability conditions and which could result in down flooding is to have scantlings not less than required for watertight bulkheads given in Pt 4, Ch 6, 7 Bulkheads. 9.1.6 The boundary bulkheads of accommodation spaces which may be subjected to blast loading are to comply with Pt 4, Ch 3, 4 Structural design loads and permissible stress levels are to satisfy the factors of safety given in Pt 4, Ch 5, 2.1 General 2.1.1. 9.1.7 The scantlings of erections used for helicopter landing areas are also to comply with Pt 4, Ch 6, 5 Helicopter landing areas. 9.1.8 For requirements relating to companionways, doors and hatches, see Pt 4, Ch 7 Watertight and Weathertight Integrity and Load Lines. 9.2 Symbols9.2.1 The following symbols and definitions are applicable to this Chapter, unless otherwise stated:
L, B,
Table 6.9.1 Values of
Table 6.9.2 Values of
9.3 Definition of tiers9.3.1 The first, or the lowest tier, is an erection situated on the deck to which D is measured. The second tier is the next tier above the lowest tier, and so on. 9.3.2 For self-elevating units where the freeboard corresponding to the required summer moulded draught for the unit can be obtained by considering the unit to have a virtual moulded depth of at least one standard superstructure height less than the Rule depth, D, measured to the uppermost continuous deck, proposals to treat the first tier erection as a second tier, and so on, will be specially considered. The standard height of superstructure is the height defined in the International Convention on Load Lines, 1966. 9.4 Design pressure head9.4.1 The design pressure head, h, to be used in the determination of erection scantlings is to be taken as: 9.4.2 In no case is the design pressure head to be taken as less than the
following:
9.5 Bulkhead plating and stiffeners9.5.1 The plating thickness, t, of fronts, sides and aft ends of all erections other than the sides of the superstructures where these are an extension of the side shell, is not to be less than: but in no case is the thickness to be less than:
9.5.2 The thickness of sides of forecastles, bridges and poops is to be as required by Pt 4, Ch 4, 4 Surface type units. 9.5.3 The modulus of stiffeners, Z, on fronts, sides and end bulkheads of all erections, other than the sides of superstructures where these are an extension of the side shell, is to be not less than: 9.5.4 The end connections of stiffeners are to be as given in Pt 4, Ch 6, 9.5 Bulkhead plating and stiffeners 9.5.5. 9.5.5 The section modulus of side frames of forecastles, bridges and poops is to be as required by Pt 4, Ch 4, 4 Surface type units. Table 6.9.3 Stiffener end connections
9.6 Erections on self-elevating units9.6.1 The scantlings of exposed ends and sides of erections are to comply with 9,5, but the additional requirements of this sub-Section are to be complied with. 9.6.2 The plating thickness, t, of exposed lower tier fronts is to be not less than: but in no case is the thickness to be less than 7,0 mm. 9.6.3 The modulus of stiffeners, Z, on exposed lowest tier fronts is to be not less than: 9.6.4 Where the exposed side of an erection is close to the side shell of the unit, the scantlings may be required to conform to the requirements for exposed bulkheads of unprotected house fronts. 9.6.5 The scantlings of jackhouses will be specially considered, but are not to be less than the scantlings that would be required for an erection at the same location. 9.6.6 The end connections of stiffeners are to be as given in Pt 4, Ch 6, 9.5 Bulkhead plating and stiffeners 9.5.5. 9.7 Erections on other unit types9.7.1 Where the erection can be subjected to wave forces, the scantlings of exposed ends and sides of erections are to comply with Pt 4, Ch 6, 9.5 Bulkhead plating and stiffeners. 9.7.2 When the erection is not subjected to wave forces in any condition then the structure is to be suitable for the maximum design loadings but the minimum scantlings of exposed sides and ends of all erections is to be not less than:
9.7.3 The modulus of stiffeners, Z, of exposed sides and ends of all erections is to be not less than: where 9.7.4 The end connections of stiffeners not subjected to wave loadings are to
be as given in Pt 4, Ch 6, 9.7 Erections on other unit types 9.7.4.
Table 6.9.4 Other unit types stiffener end connections
9.8 Deck plating9.8.1 In general, the thickness of erection deck plating is to be not less than that required by Pt 4, Ch 6, 9.8 Deck plating 9.8.2. 9.8.2 For erections not subjected to wave forces in any condition, the thickness of erection deck plating for all tiers need not exceed the requirements given in Pt 4, Ch 6, 9.8 Deck plating 9.8.2 for third tier erections, using: Table 6.9.5 Thickness of deck plating
9.8.3 When decks are fitted with approved sheathing, the thickness derived from Pt 4, Ch 6, 9.8 Deck plating 9.8.2 may be reduced by 10 per cent for a 50 mm sheathing thickness, or five per cent for 25 mm, with intermediate values in proportion. The steel deck is to be coated with a suitable material in order to prevent corrosive action, and the sheathing or composition is to be effectively secured to the deck. Inside erections the thickness may be reduced by a further 10 per cent. In no case is the deck thickness to be less than 5,0 mm. 9.9 Deck stiffening9.9.1 The requirements for deck stiffeners in this sub- Section are applicable to both beams and longitudinals. 9.9.2 Deck stiffeners on deckhouses are to have a section modulus, Z, not less than: where the load head, h6, is to be taken as not less than:
but where the deck can be subjected to weather loading, the load, h6 , is to be increased in accordance with the requirements given in Pt 4, Ch 6, 2.3 Stowage rate and design heads 2.3.2. 9.9.3 When deckhouses are subjected to specified deck loadings greater than the heads defined in Pt 4, Ch 6, 9.9 Deck stiffening 9.9.2 or are subjected to concentrated loads, equivalent load heads are to be used, see Pt 4, Ch 6, 9.9 Deck stiffening 9.9.2 or Pt 4, Ch 6, 9.9 Deck stiffening 9.9.3. 9.9.4 The section modulus of deck stiffeners on forecastles, bridges and poops is to be as required by Pt 4, Ch 4, 4 Surface type units. 9.10 Deck girders and transverse9.10.1 The scantlings of deck girders and transverses on erection decks are to
be in accordance with the requirements of Pt 4, Ch 6, 4.4 Deck supporting structure 4.4.2, using the appropriate load head, 9.11 Strengthening at ends and sides of erections9.11.1 Web frames or equivalent strengthening are to be arranged to support the sides and ends of large erections. 9.11.2 These web frames should be spaced about 9 m apart and are to be arranged, where practicable, in line with watertight bulkheads below. Webs are also to be arranged in way of large openings, boats davits and other points of high loading. 9.11.3 Arrangements are to be made to minimise the effect of discontinuities in erections. All openings cut in the sides are to be substantially framed and have well rounded corners. Continuous coamings or girders are to be fitted below and above doors and similar openings. Erections are to be strengthened in way of davits. 9.11.4 Adequate support under the ends of erections is to be provided in the form of webs, pillars, diaphragms or bulkheads in conjunction with reinforced deck beams. 9.11.5 At the corners of deckhouses and in way of supporting structures, attention is to be given to the connection to the deck, and doublers or equivalent arrangements should generally be fitted. 9.12 Unusual designs9.12.1 Where superstructures or deckhouses are of unusual design, the strength is to be not less than that required by this Section for a conventional design. 9.13 Aluminium erections9.13.1 Where an aluminium alloy complying with Ch 8 Aluminium Alloysof the Rules for Materials is used in the construction of erections, the scantlings of these erections are to be increased (relative to those required for steel construction) by the percentages given in Pt 4, Ch 6, 9.13 Aluminium erections 9.13.3. 9.13.2 The thickness, t, of aluminium alloy members is to be not less than: where 9.13.3 The minimum moment of inertia, I, of aluminium alloy stiffening members is to be not less than: where l is the effective length of the member
![]() ![]() Table 6.9.6 Percentage increase of scantlings
9.13.4 Where aluminium erections are arranged above a steel hull, details of the arrangements in way of the bimetallic connections are to be submitted. 9.13.5 For aluminium alloy helicopter decks, see Pt 4, Ch 6, 6 Decks loaded by wheeled vehicles. 9.14 Fire protection9.14.1 Fire protection of aluminium alloy erections is to be in accordance with the fire safety Regulations of the appropriate National Administration, see Pt 7, Ch 3 Fire Safety. 9.14.2 Where it is proposed to use aluminium alloy for items or equipment in hazardous areas, incendive sparking may constitute a risk and full details are to be submitted for consideration. |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|