Section 3 Loads on shell envelope
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Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Naval Ships, January 2023 - Volume 1 Ship Structures - Part 5 Environmental Loads - Chapter 3 Local Design Loads - Section 3 Loads on shell envelope

Section 3 Loads on shell envelope

Parent topic: Chapter 3 Local Design Loads

3.1 Pressures on the shell envelope

3.1.1 The design pressures for the shell envelope including exposed decks are to include the effects of combined static and dynamic load components. In addition the effects of impact or slamming loads are also to be considered, but these may be treated separately, see Vol 1, Pt 5, Ch 3, 4 Impact loads on external plating

3.1.2 The individual pressure components are given in Vol 1, Pt 5, Ch 3, 3.3 Hydrostatic pressure on the shell plating, Ph and the combined pressure to be applied to the shell envelope is given in Vol 1, Pt 5, Ch 3, 3.2 Combined hydrostatic and hydrodynamic pressure on the shell plating, Ps. The pressure to be applied to exposed and weather decks is given in Vol 1, Pt 5, Ch 3, 3.5 Pressure on exposed and weather decks, Pwd.

3.2 Combined hydrostatic and hydrodynamic pressure on the shell plating, P s

3.2.1 The total pressure distribution, P s, in kN/m2 acting on the shell plating envelope due to hydrostatic and hydrodynamic pressures is illustrated in Figure 3.3.1 Combined pressure distributution, Ps and is to be taken as specified in Table 3.3.1 Shell envelope pressure, Ps

3.3 Hydrostatic pressure on the shell plating, Ph

3.3.1 The pressure, Ph, acting on the shell plating up to the design waterline due to hydrostatic pressure is to be taken as:

Ph = 10 (Tx – (z – zk )) kN/m2
where
= Tx, z and zk are defined in Vol 1, Pt 5, Ch 3, 1.3 Symbols and definitions

3.4 Hydrodynamic wave pressure, P w

3.4.1 The hydrodynamic wave pressure distribution, P w, around the shell envelope up to the design waterline, i.e. z ≤ T x + z k, is to be taken as the greater of the following:

P m kN/m2 (relative motion)

P p kN/m2 (pitching motion)

where

P m and P p are defined in Vol 1, Pt 5, Ch 3, 3.4 Hydrodynamic wave pressure, Pw 3.4.2 and Vol 1, Pt 5, Ch 3, 3.4 Hydrodynamic wave pressure, Pw 3.4.3.

Figure 3.3.1 Combined pressure distributution, Ps

Table 3.3.1 Shell envelope pressure, P s

Vertical location Shell envelope pressure, Ps
i.e. z value kN/m2
for z ≤ T x + z k Ph + Pw
i.e. up to the design waterline  
At z = Tx + z k + Hw Pd
At z ≥ Tx + zk + 1,5Hw 0,5Pd
Symbols
Ph is the hydrostatic pressure, see Vol 1, Pt 5, Ch 3, 3.3 Hydrostatic pressure on the shell plating, Ph
Pw is the hydrodynamic wave pressure, see Vol 1, Pt 5, Ch 3, 3.4 Hydrodynamic wave pressure, Pw
Pd is the weather deck pressure, see Vol 1, Pt 5, Ch 3, 3.5 Pressure on exposed and weather decks, Pwd 3.5.2
Hw is the nominal wave limit height, see Vol 1, Pt 5, Ch 3, 3.4 Hydrodynamic wave pressure, Pw 3.4.4
Ph and Pw are to be derived at the appropriate vertical position, z
Tx, z and zk are defined in Vol 1, Pt 5, Ch 3, 1.3 Symbols and definitions

Note Pressure values at other z values are to be derived by interpolation.

3.4.2 The distribution of hydrodynamic pressure up to the design waterline, Pm, due to relative motion is to be taken as:

Pm = 10 fz Hr m kN/m2
where
fz = the vertical distribution factor
=
kz = e –u
u =

Hr m is defined in Table 3.2.1 Ship motions z,zk, Tx and LWL are defined in Vol 1, Pt 5, Ch 3, 1.3 Symbols and definitions.

3.4.3 The distribution of hydrodynamic pressure up to the design waterline due to pitching motion, Pp, is to be taken as:

Pp = 10 H pm kN/m2
where
Hpm = but not less than
where
L P = L WL but ≤ 150 m

x wl, L WL and f Hs are defined in Vol 1, Pt 5, Ch 3, 1.3 Symbols and definitions.

3.4.4 The nominal wave limit height, Hw, above the design draught, Tx, is to be taken as:

Hw = 2 Hr m m

3.5 Pressure on exposed and weather decks, P wd

3.5.1 The pressure acting on weather decks, exposed decks or decks designed for prolonged immersion, P wd, is illustrated in Figure 3.3.2 Weather deck pressure distribution, Pwd and is to be taken as specified in Table 3.3.2 Exposed/weather deck pressure, P wd

3.5.2 The minimum design pressure for weather decks, P d, above the 0,5H w limit line and below the 1,0H w limit line is to be taken as:

  • P d = 6 + 6f L f Hs kN/m2
where
f L = a location factor
  • but not less than 1,0

L WL and x wl are defined in Vol 1, Pt 5, Ch 3, 1.3 Symbols and definitions f Hs is defined in Vol 1, Pt 5, Ch 3, 1.2 Environmental conditions.

3.5.3 If a bulwark is fitted at the deck edge then consideration will be given to allowing the height of the top of the bulwark to be used for the pressure calculation.

Figure 3.3.2 Weather deck pressure distribution, Pwd

Table 3.3.2 Exposed/weather deck pressure, P wd

Vertical location Exposed/weather deck pressure, P wd kN/m2
i.e. z value
for z ≤ T x + z k P h + P w
i.e. up to the design waterline  
At z = Tx + z k + 0,5H w P d
At z = Tx + z k + 1,0H w P d
At z ≥ Tx + z k + 1,5H w 0,5P d
Symbols

P h is the hydrostatic pressure, see Vol 1, Pt 5, Ch 3, 3.3 Hydrostatic pressure on the shell plating, Ph

P w is the hydrodynamic wave pressure, see Vol 1, Pt 5, Ch 3, 3.4 Hydrodynamic wave pressure, Pw

P d is the weather deck pressure, see Vol 1, Pt 5, Ch 3, 3.5 Pressure on exposed and weather decks, Pwd 3.5.2

H w is the nominal wave limit height, see Vol 1, Pt 5, Ch 3, 3.4 Hydrodynamic wave pressure, Pw 3.4.4

P h and P w are all taken at the appropriate vertical position, z

T x, z and z k are defined in Vol 1, Pt 5, Ch 3, 1.3 Symbols and definitions

NOTE

Pressure values at other z values are to be derived by interpolation.

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