Section 3 Shell envelope
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules for the Classification of Trimarans, July 2022 - Volume 1 Regulations and Structural Arrangements - Part 5 Environmental Loads - Chapter 5 Local Design Loads - Section 3 Shell envelope

Section 3 Shell envelope

Parent topic: Chapter 5 Local Design Loads

3.1 General

3.1.1 Two design pressures are to be calculated for each item on the shell envelope; a combined pressure and an impact pressure.

3.1.2 In determining the vertical distance, z, as defined in Vol 1, Pt 5, Ch 1, 1.4 Symbols and definitions, the following applies:

  • For a longitudinally framed plate panel, is to be taken at the panel centre.
  • For a transversely framed plate panel, is to be taken at two thirds of the panel height.
  • For short stiffener members: z is to be taken at the stiffener mid position.
  • For long stiffener members: z is generally to be taken at the stiffener mid position, but may need to be specially considered, especially when there is a significant pressure variation along its length.

3.2 Combined pressure

3.2.1 The distribution of design pressures acting on the shell envelope due to static and dynamic load components, P des, is illustrated in Figure 5.3.1 Combined hydrostatic and hydrodynamic pressure distribution and taken as specified in Table Table 5.3.1 Combined Pressure Distribution .

Figure 5.3.1 Combined hydrostatic and hydrodynamic pressure distribution

Table 5.3.1 Combined Pressure Distribution

Vertical location P des kN/m2
At z ≤ T x + z k P hyd + P hys
At z = T x + z k P hyd
At z = T x + z k + H w P d
At z = T x + z k + 1,5H w 0,5P d
Symbols
P hyd, P hys and P d are to be calculated according to Vol 1, Pt 5, Ch 5, 2 Pressure components
z, T x, z k and H w are defined in Vol 1, Pt 5, Ch 1, 1.4 Symbols and definitions

Note Pressure values at other z values to be determined by linear interpolation.

3.3 Impact pressure

3.3.1 The design impact pressure is to be taken as IP bi or IP wi, according to Vol 1, Pt 5, Ch 5, 2.4 Bottom impact pressure or Vol 1, Pt 5, Ch 5, 2.5 Wave impact pressure above waterline, depending on the vertical location of the shell item.

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