Section 3 Longitudinal strength
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Inland Waterways Ships, July 2022 - Part 4 Ship Structures (Ship Types) - Chapter 9 Passenger Ships - Section 3 Longitudinal strength

Section 3 Longitudinal strength

Parent topic: Chapter 9 Passenger Ships

3.1 General

3.1.1 For the assessment of the required longitudinal strength which is to be maintained over the midship region, design bending moments are to be calculated. The design bending moments, sagging and hogging, are the maximum moments occurring when the ship is in any condition indicated in Pt 4, Ch 9, 3.1 General 3.1.5 and are to be calculated and verified for ships of a length, L, of more than 65 m and for all ships of unusual type.

3.1.2 The design bending moments are to be determined by direct calculation.

3.1.3 For ships with machinery aft, as a value for assessment of required midship section modulus, the bending moment may be taken as:

0,044 (1 – 0,86C b) L 2 B T tonne-f m, (hogging)
where
L, B, T and C b are as defined in Pt 4, Ch 9, 1.14 Symbols and definitions 1.14.1
but this value is to be verified by direct calculation for ships having a length, L, of 65 m and above.

3.1.4 For maximum permissible stresses, see Pt 3, Ch 4, 6 Hull bending strength .

3.1.5 The following loading conditions for determination of design bending moments are to be covered:

  1. Departure condition:

    Ship completely equipped, fresh water, fuel and lubricating oil tanks full, the maximum allowed number of passengers, crew and stores on board and ballast tanks are to be considered as either empty or full in accordance with the actual condition.

  2. Arrival condition:

    Ship completely equipped, fresh water, fuel and lubricating oil tanks 95 per cent empty and ballast tanks are to be considered as either empty or full in accordance with the actual condition.

  3. Any condition of the ship giving higher values of bending moments during the voyage.

3.1.6 Where an effective superstructure is fitted (see Pt 3, Ch 3, 3.4 Calculation of hull section modulus 3.4.2), it may be included in calculating the hull section modulus in way. Similarly a deckhouse may be included in calculating the hull section modulus in way, provided the longitudinal bulkheads are at least 0,75B apart, efficiently constructed, well supported, and having a length of at least 0,2L or 10 m whichever is the greater and situated within the midship region.

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