Section 1 Application
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 6 Scantling Determination - Chapter 1 Introduction - Section 1 Application

Section 1 Application

Parent topic: Chapter 1 Introduction

1.1 General

1.1.1 This Part of the Rules provides global strength requirements and local scantling requirements according to the loads calculated in Vol 1, Pt 5 Environmental Loads.

1.1.2 In addition to the requirements of this Part mandatory structural strength analysis and verification is to be carried out for all Trimarans, see Vol 4, Pt 1, Ch 2 Structural Strength Analysis and Verification.

1.2 Equivalents

1.2.1 Alternative scantlings and arrangements may be accepted as equivalent to the Rule requirements. Details of such proposals are to be submitted for consideration.

1.3 Symbols and definitions

1.3.1 The symbols and definitions for use throughout this Part are as follows:

b = actual breadth of plating, in mm, of the load bearing plating which is defined as one-half the sum of the spacings between parallel adjacent members or equivalent supports
b e = effective breadth of attached plating, see Vol 1, Pt 6, Ch 2, 2.2 Effective width of attached plating
c I = inertia coefficient dependent on the loading model assumption, see Table 4.2.1 Section modulus, inertia and web area coefficients for different load models
c A = web area coefficient dependent on the loading model assumption, see Table 4.2.1 Section modulus, inertia and web area coefficients for different load models
c Z = section modulus coefficient dependent on the loading model assumption, see Table 4.2.1 Section modulus, inertia and web area coefficients for different load models
d cd = depth of cross-deck structure, in metres, see Vol 1, Pt 6, Ch 3, 3.2 Cross-deck component stresses
d ch = the distance, in mm, measured perpendicularly from the chord length, l ch, (i.e. spacing in mm) to the highest point of the curved plating arc between the two supports, see Vol 1, Pt 6, Ch 2, 2.4 Convex curvature correction
f ar = panel aspect ratio correction factor as defined in Vol 1, Pt 6, Ch 2, 2.5 Aspect ratio correction
f curv = convex curvature correction factor as defined in Vol 1, Pt 6, Ch 2, 2.4 Convex curvature correction 2.4.1
f hts = high tensile steel factor, defined in Vol 1, Pt 6, Ch 2, 1.4 Higher tensile steel
f σ = limiting stress coefficient for local plate bending for the plating area under consideration given in Table 4.2.3 Acceptance criteria in Chapter 4
f σhg = limiting hull bending stress coefficient, see Vol 1, Pt 6, Ch 3, 2.4 Longitudinal bending strength
f σws = limiting working stress coefficient, see Vol 1, Pt 6, Ch 3, 2.5 Minimum hull section modulus
k l = higher tensile steel factor for local loads, see Vol 1, Pt 6, Ch 2, 1.4 Higher tensile steel
k g = higher tensile steel factor for global loads, see Vol 1, Pt 6, Ch 2, 1.4 Higher tensile steel
l = overall length of stiffener or primary member, in metres
l ch = chord length between stiffeners in mm, see Vol 1, Pt 6, Ch 2, 2.4 Convex curvature correction
l e = effective span length, in metres
n bhd = number of transverse bulkheads in the longitudinal cross-deck section
s = secondary stiffener spacing, in mm
t bhd = cross-deck structure transverse bulkhead plating thickness, in mm
t dk = deck plating thickness in way of cross-deck structure, in mm
t p = plating thickness, in mm
z = vertical distance, in metres, from the hull transverse neutral axis to a position under consideration
z i = section modulus of cross-deck beam, in cm3, see Vol 1, Pt 6, Ch 3, 3.2 Cross-deck component stresses
z m = vertical distance, in metres, from the hull transverse neutral axis to the minimum limit of higher tensile steel, above or below the neutral axis as appropriate
z B = the vertical distance, in metres, from the transverse neutral axis of the total hull cross-section to the top of the keel
z D = the vertical distance, in metres, from the transverse neutral axis of the total hull cross-section to the uppermost continuous longitudinally effective material
A cd = total vertical shear area of a longitudinal cross section of the cross-deck structure, extending only the length of the side hull, in cm2. Initially only transverse bulkheads with breadth including the main hull, side hulls and cross-deck structure will be considered effective in shear
A wi = shear area of cross deck beam web, in cm2, see Vol 1, Pt 6, Ch 3, 3.2 Cross-deck component stresses
A R = panel aspect ratio
= panel length/panel breadth
A T = effective shear area of transverse section, in m2, to be taken as the net effective sectional area of the side shell plating and the longitudinal bulkheads after deductions for openings
E = modulus of elasticity, in N/mm2
F B = local scantling reduction factor for hull members below the neutral axis, see Vol 1, Pt 6, Ch 3, 2.3 Higher tensile steel 2.3.2
F D = local scantling reduction factor for hull members above the neutral axis, see Vol 1, Pt 6, Ch 3, 2.3 Higher tensile steel 2.3.2
I = moment of inertia, in cm4
I i = moment of inertia of cross deck beam, in cm4, see Vol 1, Pt 6, Ch 3, 3.2 Cross-deck component stresses
I cd = total inertia of a longitudinal cross section of the cross-deck structure, extending only the length of the side hull, in cm4
M tot = total Rule bending moment, in kNm, given in Vol 1, Pt 5, Ch 4, 2.8 Longitudinal hull girder design loads
M wHog = hogging value of M w, in kNm, given in Vol 1, Pt 5, Ch 4, 2.4 Vertical wave bending moment
M wSag = sagging value of M w, in kNm, given in Vol 1, Pt 5, Ch 4, 2.4 Vertical wave bending moment
P des = design pressure, in kN/m2, for structural item under consideration, as calculated according to Vol 1, Pt 5, Ch 5 Local Design Loads
S = primary stiffener spacing, in metres
S bhd = spacing of transverse bulkheads in the cross-deck structure, in metres
Z cdb = section modulus at the bottom, or wet deck, of a longitudinal section of the cross-deck structure, extending only the length of the side hull, in cm3
Z cdt = section modulus at the top, typically the main deck, of a longitudinal section of the cross-deck structure, extending only the length of the side hull, in cm3
Z curv = section modulus, in cm3, of transverse main and ‘tween deck frames, corrected for convex curvature
Z i = actual section modulus at structural element being considered, in cm3
Z i = section modulus of general stiffening member, in cm3
σB = maximum hull vertical bending stress at keel in N/mm2, see Table 3.2.1 in Chapter 3
σD = maximum hull vertical bending stress at strength deck in N/mm2, see Table 3.2.1 in Chapter 3
σp = permissible combined stress in N/mm2, see Vol 1, Pt 6, Ch 3, 2.4 Longitudinal bending strength 2.4.3
σsph = direct stress on transverse primary member due to hog splitting load, in N/mm2
σsps = direct stress on transverse primary member due to sag splitting load, in N/mm2
σtt = direct stress on transverse primary member due to transverse torsional moment, in N/mm2
σyd = guaranteed minimum yield strength of the material in N/mm2
σydMild = minimum yield strength of mild steel in N/mm2
σu = ultimate tensile strength of the material in N/mm2
σws = hull girder bending stress range in N/mm2, see Vol 1, Pt 6, Ch 3, 2.4 Longitudinal bending strength
τsp = shear stress induced by the splitting shear force, in N/mm2
τtt = shear stress induced by the transverse torsional moment, in N/mm2
τyd = shear strength of the material in N/mm2
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