Section 15 Requirements for ships with large deck openings

15.1.1 The combined stresses due to vertical bending moment, horizontal bending moment and torque are to be calculated as described in this Section.

15.2.1 The following symbols and definitions are applicable to this Section unless otherwise stated:

15.3.1 The design vertical wave bending moments, M_WC1 and M_WC2, at any position along the ship is defined as:

L, B, C_b are given in Pt 3, Ch 1, 6 Definitions

The sign convention is given in Figure 8.15.1 Sign conventions for hull girder loads

15.3.2 The design horizontal wave bending moments, M_HC1 and M_HC2, at any position along the ship are defined as:

C ₀ is defined in Pt 4, Ch 8, 15.3 Design loadings 15.3.1
L, T ,C _b are given in Pt 3, Ch 1, 6 Definitions

The sign convention is given in Figure 8.15.1 Sign conventions for hull girder loads

15.3.3 The design hydrodynamic torques, M_WTC1 and M_WTC2, at any position along the ship are defined as:

C ₀ is defined in Pt 4, Ch 8, 15.3 Design loadings 15.3.1

L, B, T, C_b, are given in Pt 3, Ch 1, 6 Definitions.
ε is given in Pt 4, Ch 8, 15.2 Symbols and definitions 15.2.1

The sign convention is given in Figure 8.15.1 Sign conventions for hull girder loads

15.3.4 The value and distribution of static cargo torque, M_STC, are to be specified by the designer based on the intended operation of the ship and are not to be less than minimum design value of static cargo torque. The minimum design value of static cargo torque, M_STC, at any position along the ship is defined as:

B is given in Pt 3, Ch 1, 6 Definitions.

15.4.1 Combined stress calculations are to be carried out at least at the following positions along the length of the ship:

1. At the forward and aft ends of the engine room.

2. At the forward and aft ends of the deck-house for multi-island designs.

3. At the forward and aft transverse bulkhead positions of each cargo bay.

4. At the forward and aft transverse bulkhead of fuel oil deep tanks.

5. At any other sections where there are significant changes in cross-section properties.

15.4.2 The combined stress, σ_c, is to be less than the permissible stress given in Table 8.15.4 Permissible stress. σ_c, is to be taken as the greatest magnitude of the following stresses:

where

For σ_C1

where

For σ'_C1

For σ'_C2

where

other symbols are as defined in Pt 4, Ch 8, 15.3 Design loadings and Pt 4, Ch 8, 15.4 Combined stress.

15.4.3 For ships with a beam greater than 32,26 m, longitudinal stresses are to be calculated using a finite element model of the entire hull in accordance with Part A of the LR’s ShipRight SDA procedure for container ships.

15.4.4 For ships with a beam less than or equal to 32,26 m, the longitudinal stresses may be obtained as follows:

σ_WTC1, σ_WTC2 and σ_STC are to be evaluated by approved calculation procedures.

Z _y and Z _z are given in Pt 4, Ch 8, 15.2 Symbols and definitions 15.2.1.

15.4.5 At each section the stresses are to be calculated on the port and starboard sides, at:

1. the inboard edge of the strength deck;

2. the point on the bilge where the combined stress is greatest; and

3. the top of continuous hatch coaming (where fitted).

15.4.6 Where the ship’s length is greater than 425 m or the ship’s beam is greater than 60 m, the vertical wave bending moments, horizontal wave bending moments and hydrodynamic torques are to be obtained from a direct calculation method. Alternatively, the hull stresses may be obtained using a probabilistic approach response-based analysis method considering the ship’s responses in wave environment. The analysis method is to be agreed with LR.

15.5.1 The maximum tensile or compressive combined stress σ_c at any position along the length is not to be more than indicated in Table 8.15.4 Permissible stress.

15.5.2 The assessment of combined stress may conveniently be presented in the form of combined stress diagrams as indicated in Figure 8.15.2 Combined stress diagram for deck - Oblique sea.