Section 13 Direct calculation procedures
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Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Inland Waterways Ships, July 2022 - Part 4 Ship Structures (Ship Types) - Chapter 1 Dry Cargo Ships - Section 13 Direct calculation procedures

Section 13 Direct calculation procedures

Parent topic: Chapter 1 Dry Cargo Ships

13.1 General

13.1.1 This Section contains guidance for direct calculations, information regarding maximum permissible stresses and minimum requirements for structural members included in the hull midship section modulus and for other structural members which do not form part of the hull midship section modulus.

13.1.2 Where direct calculation is adopted as an alternative of scantlings derived by Rule formulae, or for the asessment of scantlings of structural members not covered by the Rules, all data in support of the calculation, i.e. support conditions and loads are to be submitted for approval together with the calculation.

13.2 Permissible stresses

13.2.1 In addition to the permissible stresses given inPt 3, Ch 4, 6 Hull bending strength , the following stress criteria are to be applied:

  1. For structural members included in the hull section modulus the maximum bending stresses, shear stresses and equivalent stresses are not to exceed the values given in Table 1.13.1 Maximum permissible stress in longitudinal continuous members, in N/mm2 .

  2. For structural members not included in the hull section modulus, the maximum bending stresses, shear stresses and equivalent stresses are not to exceed the values given in Table 1.13.2 Maximum permissible stresses in local members, in N/mm2 .

13.2.2 Where finite plate element calculations are carried out, local peak stresses in excess of those given in Pt 4, Ch 1, 13.2 Permissible stresses 13.2.1 will be specially considered.

Table 1.13.1 Maximum permissible stress in longitudinal continuous members, in N/mm2

Item Local bending stress, σb Combined bending stress, σc, see Note 1 Shear stress τ Equivalent stress, σ e, see Note 2
Bottom girders 0,46σL 0,75σL 0,35σL 0,80σL
Bottom longitudinals, 0,58σL 0,75σL 0,35σL 0,80σL
Inner bottom longitudinals,
Side shell longitudinals

where σL = 235/kL

Note 1 The combined stress, σ c, is the sum of the stress due to longitudinal bending and local loading.

Note 2. The equivalent stress, σ e, is to be calculated according to the formula σe =

Table 1.13.2 Maximum permissible stresses in local members, in N/mm2

Item Bending stress, σb Shear stress, τ Equivalent stress, σe see Note
Floors, non-continuous bottom girders, 0,53σO 0,35σO 0,75σO
non-continuous deck girders, deck transverses,
cantilever brackets

Note The equivalent stress, σ e, is to be calculated according to the formula σ e =

13.3 Structural requirements

13.3.1 As a first approximation the structural components may be determined according to the requirements of the preceding Sections of this Chapter.

13.3.2 In addition to the maximum permissible stresses given in this Section, the following minimum plating thickness requirements are to be complied with. The thickness of bottom, bilge and side shell plating amidships is to be not less than required by Table 1.5.1 Shell envelope plating. The minimum thickness of the deck plating and coaming plating is to be not less than required by Table 1.4.1 Topside structure (general). Depending on the level of compressive stresses, additional buckling calculations may be required.

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