Section 3 Global cross-deck loads
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 4 Global Design Loads - Section 3 Global cross-deck loads

Section 3 Global cross-deck loads

Parent topic: Chapter 4 Global Design Loads

3.1 Splitting moment

3.1.1 The splitting moments, for hog, M sph, and for sag, M sps, illustrated in Figure 4.3.1 Splitting moment are to be given by the following:

where
= Points I and O are given in Figure 4.3.2 Distances and locations for splitting loads. Moment values at locations on the cross-deck between I and O are to be linearly interpolated. If the cross-deck structure is radiused, points I and O are to be taken as the points where the tangents lines are at 45° from the horizontal.
W hs = the total weight of one side hull, in tonnes, including lightship weight and deadweight, see Vol 1, Pt 5, Ch 1, 1.4 Symbols and definitions. For preliminary design purposes, this value may be estimated as a proportion of the total displacement according to the ratio of the side hull volume to the total volume. This weight is to be calculated according to the actual weight distribution before final submission to LR
f serv = is defined in Vol 1, Pt 5, Ch 4, 2.4 Vertical wave bending moment 2.4.1
a z = is defined in Vol 1, Pt 5, Ch 3, 2.2 Design accelerations. The a rollz component of a z is to be calculated at a position y = y sh
= B mh, B sh, ∆ and ∆mh are defined in Vol 1, Pt 1, Ch 1, 5.2 Principal particulars.

Figure 4.3.1 Splitting moment

Figure 4.3.2 Distances and locations for splitting loads

3.2 Splitting shear force

3.2.1 The splitting shear force, Q sph, corresponding to the hogging condition and Q sps, corresponding to the sagging condition are uniform along the breadth of the cross-deck structure and are to be calculated as follows:

where
W sh = is defined in Vol 1, Pt 5, Ch 4, 3.1 Splitting moment
f serv = is defined in Vol 1, Pt 5, Ch 4, 2.4 Vertical wave bending moment 2.4.1
∆ = is defined in Vol 1, Pt 1, Ch 1, 5.2 Principal particulars
a z = is defined in Vol 1, Pt 5, Ch 3, 2.2 Design accelerations. The a rollz component of a z is to be calculated at a position y =y sh.

3.3 Transverse torsional moment

3.3.1 The transverse torsional moment, M tt, as illustrated in Figure 4.3.3 Transverse torsional moment is uniform along the breadth of the cross-deck structure and is to be given by the following:

Figure 4.3.3 Transverse torsional moment
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