Section 3 Primary steel support member scantling determination
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Clasifications Register Rules and Regulations - Rules for the Application of Sandwich Panel Construction to Ship Structure, July 2022 - Chapter 4 Design Basis and Scantling Determination of Primary Structure - Section 3 Primary steel support member scantling determination

Section 3 Primary steel support member scantling determination

Parent topic: Chapter 4 Design Basis and Scantling Determination of Primary Structure

3.1 General

3.1.1 The requirements for section modulus and inertia (if applicable) of primary support members are given in the appropriate Chapters of Pt 3 Ship Structures (General) and Pt 4 Ship Structures (Ship Types) of the Rules and Regulations for the Classification of Ships, July 2022.

3.1.2 The requirements for proportions, stiffening and construction details of primary steel supporting members are given in Pt 3, Ch 10, 4 Construction details for primary members of the Rules and Regulations for the Classification of Ships, July 2022. The plate thickness requirement for deck plating forming the upper flange of underdeck girders in Table 10.4.1 Minimum thickness of primary members item (3) is to be applied to the combined thickness of the top and bottom plating of the steel sandwich panel.

3.1.3 In addition, where the primary steel support member contributes to the global strength of the ship, the thickness is to be not less than that required to satisfy the global strength requirements detailed in Pt 3, Ch 4 Longitudinal Strength of the Rules and Regulations for the Classification of Ships, July 2022.

3.2 Geometrical properties of primary steel support member

3.2.1 In cases where the primary steel support member is not connected to both the bottom and top plating, see Figure 4.3.1 Top plate thickness reduction (for illustration only), the section modulus of the primary steel support member is to be calculated by reducing the thickness of the top plating:

where
t1R = reduced thickness of the top plating, in mm
t1 = minimum required thickness of the top plating, in mm, see Ch 3, 4 Panel scantling requirements
α =
tc, d = see Ch 3, 4 Panel scantling requirements.

Figure 4.3.1 Top plate thickness reduction (for illustration only)

3.3 Corrosion margins

3.3.1 The requirements for primary steel support member calculated according to the Rules and Regulations for the Classification of Ships, July 2022 include a corrosion margin. No additional corrosion margin is required.

3.4 Effective breadth

3.4.1 The section moduli of the primary steel support members given by these requirements are to be determined in association with the effective attached plating as specified in Pt 3, Ch 3, 3.2 Geometric properties of section of the Rules and Regulations for the Classification of Ships, July 2022.

3.5 Hull girder strength

3.5.1 For all ships, the hull girder strength requirements of Pt 3, Ch 4 Longitudinal Strength of the Rules and Regulations for the Classification of Ships, July 2022 are to be complied with.

3.5.2 The scantling distribution of primary steel support members contributing to the hull girder strength is to be carefully selected so as to avoid structural discontinuities resulting in abrupt variations of stress.

3.5.3 All continuous longitudinal structurally effective material is to be included in the calculation of the hull girder strength, of the hull midship section. The lever, may be measured vertically from the neutral axis to the centre of the steel sandwich panel.

3.5.4 The effective geometric properties of the midship section are to be calculated directly from the dimensions of the section using only the effective material elements which contribute to the global longitudinal strength.

3.6 Decks

3.6.1 The scantlings of primary steel support members are not to be less than those given in:

3.7 Decks loaded by wheeled vehicles

3.7.1 The primary steel support members for decks loaded with wheeled vehicles are to be in accordance with Pt 3, Ch 9, 3 Decks loaded by wheeled vehicles of the Rules and Regulations for the Classification of Ships, July 2022.

3.8 Superstructure

3.8.1 This sub-Section contains scantling requirements applicable to the internal decks of superstructure. All internal decks are to be evaluated according to Ch 4, 3.8 Superstructure 3.8.2.

3.8.2 The section modulus of primary steel support members is to be in accordance with the applicable rules of the Rules and Regulations for the Classification of Ships, July 2022, see Table 4.3.1 Applicable Rules.

Table 4.3.1 Applicable Rules

Type of Ship Applicable Rules
All types of ships, except: Pt 3, Ch 8 Superstructures, Deckhouses and Bulwarks
  Deckhouses situated on forecastles of offshore supply ships Pt 4, Ch 4 Offshore Support Vessels
Ferries, Roll on-Roll-of ships and Passenger Ships Pt 4, Ch 2 Ferries, Roll On-Roll Off Ships and Passenger Ships

3.9 Double bottom

3.9.1 The scantlings of primary steel support members in the double bottom are not to be less than those given in:

3.10 Shell envelope

3.10.1 The scantlings of primary steel support members are not to be less than those given in:

3.10.2 Where applicable, bottom and side shell structure below the waterline is to be evaluated against the slamming requirements in Pt 3, Ch 5, 1.5 Strengthening of bottom forward of the Rules and Regulations for the Classification of Ships, July 2022.

3.10.3 Side shell structure above the waterline is not to be less than those given in Pt 3, Ch 5, 1.6 Strengthening against bow flare slamming, Pt 4, Ch 2 Ferries, Roll On-Roll Off Ships and Passenger Ships and Pt 4, Ch 8 Container Ships of the Rules and Regulations for the Classification of Ships, July 2022 depending on the particular ship type.

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