Section 7 Component design loads
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Special Service Craft, July 2022 - Part 5 Design and Load Criteria - Chapter 2 Local Design Loads - Section 7 Component design loads

Section 7 Component design loads

Parent topic: Chapter 2 Local Design Loads

7.1 Deckhouses, bulwarks and superstructures

7.1.1 The component design pressure, Pdhp, for the plating of deckhouses, bulwarks and first tier and above superstructures is given by:

Gf and Sf are defined in Pt 5, Ch 3 Local Design Criteria for Craft Operating in Non-Displacement Mode or Pt 5, Ch 4 Local Design Criteria for Craft Operating in Displacement Mode as appropriate.

Pd is defined in Pt 5, Ch 2, 4.5 Pressure on weather and interior decks.

For structures other than windows:

C1 = 1,25 for deckhouse and superstructure fronts on upper deck within the forward third of LR
= 1,15 for deckhouse and superstructure fronts on upper deck outside the forward third of LR and exposed machinery casings on the upper deck
= 1,0 for deckhouse and superstructure fronts above the lowest tier
= 0,8 for superstructure sides. A value of 0,64 may be used where the sides of the superstructure are stepped in from the sides of the craft by 1,0 m or more
= 0,5 elsewhere
LR = Rule length in metres, see Pt 5, Ch 2, 2.2 Symbols 2.2.1

For windows of toughened safety glass the component design pressure, Pdhp, is to be calculated taking C1 as follows:

For windows positioned on the first tier, C1 is not to be taken less than that used for the deckhouse plating Pd for windows may be tapered to 0,5Pd in accordance with Table 2.4.1 Combined pressure distribution, Ps .

where
W1 = 2,0 for the lowest tier of unprotected front
= 1,5 for superstructure fronts above the lowest tier
= 1,0 for superstructure sides. A value of 0,8 may be used where the sides of the superstructure are stepped in from the sides of the craft by 1,0 metre or more
= 0,67 elsewhere
W2 = 0,67 + 0,33 (x b/L WL) where x b > 0,5L WL from AP
= 0,67 elsewhere
W3 = 1 – (y – F)/y
xb = distance, in metres, from AP
y = vertical distance, in metres, from the static load waterline at the deepest design draught to the structural element considered
F = (D – T) in metres

Gf and Sf are defined in Pt 5, Ch 3 Local Design Criteria for Craft Operating in Non-Displacement Mode or Pt 5, Ch 4 Local Design Criteria for Craft Operating in Displacement Mode as appropriate. Pd is defined in Pt 5, Ch 2, 4.5 Pressure on weather and interior decks.

LWL, D and T are as defined in Pt 3, Ch 1, 6.2 Principal particulars.

7.2 Watertight and deep tank bulkheads

7.2.1 The design pressure, Pbh, on watertight and deep tank bulkheads is to be taken as:
Pbh = 11,2 hb kN/m2 for:
  • deep tank bulkheads,
  • watertight bulkhead doors and
  • stiffening supporting watertight bulkheads in way of watertight doors
where
hb = load head in metres, measured as described in (b)
= 7,2 hb kN/m2 for:
  • watertight bulkhead plating and
  • stiffening clear of watertight doors
where
h b = load head in metres, measured as described below in (a) for deep tank bulkheads and (c) for doors

  1. Watertight bulkheads:

    1. Plating: the distance from a point one-third of the height of the plate above its lower edge to the bulkhead deck at side.

    2. Stiffeners: the distance from the mid-point of the stiffener span to the bulkhead deck at side.

  2. Deep tank bulkheads:

    For determination of head, the overflow is to be taken as not less than 1,8 m above the crown of the tank.

    1. Plating: the greater of:

      • the distance from the point one-third of the height of the plate above its lower edge to the top of the tank
      • half the distance from a point one third of the height of the plate above its lower edge to the top of the overflow.

    2. Stiffeners: the greater of:

      • the distance from the mid-point of the span to the top of the tank
      • half the distance from mid-point of span to the top of the overflow.
  3. Watertight door and supporting construction
    1. Plating: the distance from the point one-third of the height of the plate above its lower edge to the main deck
    2. Stiffeners: the distance from the mid-point of the span the main deck

7.3 Pillars

7.3.1 The design load, P PI, supported by a pillar is to be taken as:

where
P c = basic deck girder design pressure, as appropriate, plus any other loadings directly above the pillar, in kN/m2
P a = load, in kN, from pillar or pillars above, assumed zero if there are no pillars over
S gt = spacing, or mean spacing, of girders or transverses, in metres
b gt = distance between centres of two adjacent spans of girders or transverses supported by the pillar, in metres

P PI is not to be taken less than 5 kN.

7.4 Deck area designed for cargo, stores and equipment

7.4.1 The cargo deck design pressure, P cd, for plating is to be taken as:

where a x is given in Pt 5, Ch 2, 3.2 Vertical acceleration 3.2.7 and is not to be taken as less than 1,0.

W CDP is the pressure exerted by the cargo on deck specified by the designer in kN/m2.

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