Section 12 Strengthening for wave impact loads

12.1.1 The scantlings of plating, stiffeners of forward and after portions of the hull are to be increased for protection against bow flare and wave impact pressure in accordance with Pt 4, Ch 2, 4.3 Strengthening for wave impact loads and Pt 4, Ch 2, 5.2 Strengthening for wave impact loads.

12.1.2 The scantlings of the primary support structure are to be adequate to resist the application of the Rule slamming load, P_bf, as defined in Pt 4, Ch 2, 4.2 Bow flare and wave impact pressures 4.2.1, over an area A_sl, as shown in Figure 2.5.2 Mean spacing between primary members, S _cm, and the extents of wave impact pressure g _bfh and g _bfv in Pt 4, Ch 2 Ferries, Roll On-Roll Off Ships and Passenger Ships. The loaded area, A_sl, is a rectangle with a horizontal extent, g_bfh, and vertical extent, g_bfv, taken as follows:

where

K_bf and β_p are given in Pt 4, Ch 2, 4.2 Bow flare and wave impact pressures 4.2.1.

12.1.3 To satisfy Pt 4, Ch 8, 12.1 General 12.1.2, the scantlings of web frames supporting side longitudinals or side stringers supporting transverse frames are to comply with the following:

1. Section modulus not to be less than:

   Z

   =

   3,75f rpc γZ k hs q v le 2 cm3

2. Web area not to be less than:

   A	=	0,20f rpc γA k hs q v le cm2
   	=	where
   hs	=	wave impact head, in metres, as defined in Pt 4, Ch 2, 4.3 Strengthening for wave impact loads 4.3.2.
   	=	and
   f rpc	=
   	=
   P	=	is the maximum propulsion shaft power in kW for which the machinery is classed, see Pt 5, Ch 1, 3 Operating conditions
   H	=	is the maximum propulsion shaft power in HP for which the machinery is classed, see Pt 5, Ch 1, 3 Operating conditions
   V	=	is the speed, in knots as defined in Pt 3, Ch 1, 6 Definitions
   	=	γA and γZ are strength factors dependent on the load position:
   	=	for q < 1:γA = q3 – 2q2 + 2 and γZ = 3q3 – 8q2 + 6q
   	=	for q = 1:γA = 1γZ = 1
   q	=	but ≤ 1
   	=	for web frames
   u	=	is the minimum of gbfv or le
   v	=	is the minimum of gbfh or S cm
   	=	for side stringers
   u	=	is the minimum of gbfh or le
   v	=	is the minimum of gbfv or Scm
   le	=	is the effective length of the primary member, in metres
   Scm	=	is the mean spacing between primary members along the plating, in metres, see Figure 2.5.2 Mean spacing between primary members, S cm, and the extents of wave impact pressure g bfh and g bfv in Pt 4, Ch 2 Ferries, Roll On-Roll Off Ships and Passenger Ships
   	=	g bfv and g bfh are defined in Pt 4, Ch 8, 12.1 General 12.1.2

3. Web plating is to be adequately stiffened to resist shear buckling as required by Table 8.12.1 Critical shear buckling stress for web plating of primary support structure.