Section 2 Design accelerations

2.1.1 The non-dimensional ship motion acceleration values given in this Section are to be used in the calculation of global and local loads. The equations given here are applicable to ships with trimaran hull forms operating in the displacement mode at their normal ship service speed or cruising speed. Any ships operating in the planing regime are to be specially considered.

2.2.1 The heave acceleration, a _heave, is to be calculated in terms of g as follows:

• where
• f _wv is given in Table 3.2.1 Wave height factor, f _wv
• V is an appropriate design speed, defined as follows:
• = V _crfor determination of local and global loads
• = V _spfor determination of impact pressures if the Complementary Rules are the Rules and Regulations for the Classification of Naval Ships (hereinafter referred to as the Rules for Naval Ships) f _wv, V _cr and V _sp are defined in Vol 1, Pt 5, Ch 1, 1.4 Symbols and definitions
• L _wl is defined in Vol 1, Pt 1, Ch 1, 5.2 Principal particulars.

2.2.2 The vertical acceleration due to roll, a _rollz, is to be calculated in terms of g as follows:

• a _heave is defined in Vol 1, Pt 5, Ch 2, 2.2 Service areas and factors 2.2.1
• GM and y are defined in Vol 1, Pt 5, Ch 1, 1.4 Symbols and definitions
• B _wltot is defined in Vol 1, Pt 1, Ch 1, 5.2 Principal particulars.

2.2.3 The vertical acceleration, a _z, due to roll and heave, at a position y, is to be calculated as follows:

y is defined in Vol 1, Pt 5, Ch 1, 1.4 Symbols and definitions.

2.2.4 The wave head due to relative vertical motion, H _rm is to be calculated as follows:

• f _ld varies according to the type of load being calculated as follows:

• V is defined in Vol 1, Pt 5, Ch 3, 2.2 Design accelerations 2.2.1
• x _wl and g are defined in Vol 1, Pt 5, Ch 1, 1.4 Symbols and definitions
• L _wl, C _b is defined inVol 1, Pt 1, Ch 1, 5.2 Principal particulars.