2.2 Still water bending moments

2.2.1 The design still water bending moments MSW,H and MSW,S at any hull transverse section are the maximum still water bending moments calculated, in hogging and sagging conditions, respectively, at that hull transverse section for the loading conditions specified in [2.1.2].Where no sagging bending moments act in the hull section considered, the value of MSW,S is to be taken as specified in Part B, Chapter 6 and Part B, Chapter 7.

2.2.2 If the design still water bending moments are not defined, at a preliminary design stage, at any hull transverse section, the longitudinal distributions shown in Fig 2 may be considered.In Fig 2, MSW is the design still water bending moment amidships, in hogging or sagging conditions, whose absolute values are to be taken not less than those obtained, in kN.m, from the following formulae:

hogging conditions:

sagging conditions:

where MWV,H, MWV,S are the vertical wave bending moments, in kN.m, defined in [3.1].

Figure 2 : Preliminary still water bending momentdistribution

till water shear force

2.3.1 The design still water shear force QSW at any hull transverse section is the maximum positive or negative shear force calculated, at that hull transverse section, for the loading conditions specified in [2.1.2].

Vertical wave bending moments

3.1.1 The vertical wave bending moments at any hull transverse section are obtained, in kN.m, from the following formulae:

hogging conditions:MWV,H = 190FM n C L2 B CB 10-3

sagging conditions:MWV,S = - 110FM n C L2 B (CB + 0,7) 10-3

where:FM : Distribution factor defined in Tab 1 (see also Fig 3).

Table 1 : Distribution factor FM

Hull transverse section location Distribution factor FM

0 <= x < 0,4 L

0,4 L <= x <= 0,65 L 1

065 L < x <= L

Figure 3 : Distribution factor FM

3.1.2 The effects of bow flare impact are to be taken into account, for the cases specified in [4.1.1], according to [4.2.1].

Horizontal wave bending moment

3.2.1 The horizontal wave bending moment at any hull transverse section is obtained, in kN.m, from the following formula:MWH = 0,42FM n H L2 T CB

where FM is the distribution factor defined in [3.1.1].

Wave torque

3.3.1 The wave torque at any hull transverse section is to be calculated considering the ship in two different conditions:

condition 1: ship direction forming an angle of 60o with the prevailing sea direction

condition 2: ship direction forming an angle of 120o with the prevailing sea direction.

The values of the wave torques in these conditions, calculated with respect to the section centre of torsion, are obtained, in kN.m, from the following formula: 

where:FTM, FTQ : Distribution factors defined in Tab 2 for ship conditions 1 and 2 (see

also Fig 4 and Fig 5)

CM : Wave torque coefficient:CM = 0,45 B2 CW

2

CQ : Horizontal wave shear coefficient:CQ = 5 T CB

CW : Waterplane coefficient, to be taken not greater than the value obtained from the following formula:CW = 0,165 + 0,95 CB where CB is to be assumed not less than 0,6. In the absence of more precise determination, CW may be taken equal to the value provided by the above formula.

d : Vertical distance, in m, from the centre of torsion to a point located 0,6 T above the baseline.

Table 2 : Distribution factors FTM and FTQ

Shipcondition

Distribution factor FTM Distribution factor FTQ

1

2

Figure 4 : Ship condition 1Distribution factors FTM and FTQ

Figure 5 : Ship condition 2Distribution factors FTM and FTQ

Vertical wave shear force

3.4.1 The vertical wave shear force at any hull transverse section is obtained, in kN, from the following formula:QWV = 30 FQ n C L B (CB + 0,7) 10-2

where:

FQ : Distribution factor defined in Tab 3 for positive and negative shear forces (see also Fig 6).