Section 5 Design bending moments
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Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Inland Waterways Ships, July 2022 - Part 3 Ship Structures (General) - Chapter 4 Longitudinal Strength - Section 5 Design bending moments

Section 5 Design bending moments

Parent topic: Chapter 4 Longitudinal Strength

5.1 General

5.1.1 The design bending moments, sagging and hogging, are the maximum moments occurring when the ship is in any condition indicated in Pt 3, Ch 4, 2.1 Loading conditions for determination of design bending moments.

5.1.2 The design bending moments may be determined, using the formulae given in this Section, but will be verified by direct calculations for ships with unusual or non-uniform load distribution and for ships of a length, L, exceeding 65 m or as specified in Pt 4, Ch 5, 4.1 Longitudinal strength requirements, Pt 4, Ch 6, 2.1 Longitudinal strength requirements and Pt 4, Ch 7, 3.1 General 3.1.1.

5.2 Calculation of design bending moment using formulae

5.2.1 The design bending moments (still water condition) to be distinguished and the formulae to be used are given in Table 4.5.1 Design bending moments and Table 4.5.2 Design bending moments in relation to longitudinal strength category.

Table 4.5.1 Design bending moments

  Self-propelled
ships 		Non-propelled
ships
Hogging Sagging Hogging Sagging
Ships of longitudinal strength, Category 'T' MH T The greater of: MS T, or MS lo MH T MS T
Ships of longitudinal strength, Category 'O' MH O MS O MH O MS O
Symbols (applicable to Table 4.5.1 Design bending moments and Table 4.5.2 Design bending moments in relation to longitudinal strength category)
L, B, D ,T and C b are defined in Pt 3, Ch 1, 6 Definitions
r = ratio of
L c = length of hold(s) for dry cargo ships
= cargo compartment length excluding cofferdams at fore and aft end for tankers
MH O = Hogging moment of ships with loading sequence 'O', see Pt 3, Ch 4, 2.1 Loading conditions for determination of design bending moments 2.1.1.(c)
MH T = Hogging moment of ships with loading sequence 'T', see Pt 3, Ch 4, 2.1 Loading conditions for determination of design bending moments 2.1.1.(c)
MS O = Sagging moment of ships with loading sequence 'O', see Pt 3, Ch 4, 2.1 Loading conditions for determination of design bending moments 2.1.1.(c)
MS T = Sagging moment of ships with loading sequence 'T', see Pt 3, Ch 4, 2.1 Loading conditions for determination of design bending moments 2.1.1.(c)

Table 4.5.2 Design bending moments in relation to longitudinal strength category

Moment,
in tonne-f m 		Self-propelled ships Non-propelled ships
MH li (0,9 – 0,0013L) x MH O  
MH O (1,98r – 0,45) (K 1 BT + K 2 ) L 2 (0,0166 – 0,0088C b ) L 2 BT × (3,97r - 2,414)
MH T 0,92 x MH O (2,23 - 1,67C b ) MH O
MS lo (0,118C b - 0,0958)L 2 BT + 0,092 (0,73 - r ) L 2 BT (0,95C b – 0,0806) L 2 BT + 0,1 (0,86 – r )L 2 BT
MS O (K 3 BT – K 4 ) L 2 + (0,24C b – 0,148) (0,73 – r ) x L 2 BT (0,091C b – 0,068) L 2 BT × (4,18 – 3,7r )
MS T (2C b – 1,08) × MS O (2C b – 1,08) MS O
For symbols, see Table 4.5.1 Design bending moments and Table 4.5.3 Self-propelled ships with machinery aft

Table 4.5.3 Self-propelled ships with machinery aft

Block coefficient
C b 		Hogging moment Sagging moment
K1 K2 K3 K4
0,75 0,01039 0,07512 0,00668 0,08080
0,76 0,01050 0,07329 0,00741 0,08149
0,77 0,01058 0,07147 0,00817 0,08217
         
0,78 0,01064 0,06964 0,00895 0,08284
0,79 0,01067 0,06782 0,00975 0,08350
0,80 0,01068 0,06599 0,01056 0,08415
         
0,81 0,01066 0,06416 0,01139 0,08479
0,82 0,01061 0,06234 0,01225 0,08542
0,83 0,01054 0,06052 0,01312 0,08604
         
0,84 0,01044 0,05869 0,01401 0,08665
0,85 0,01031 0,05687 0,01492 0,08724
0,86 0,01015 0,05504 0,01584 0,08783
         
0,87 0,00997 0,05322 0,01679 0,08841
0,88 0,00976 0,05140 0,01775 0,08898
0,89 0,00953 0,04958 0,01874 0,08953
         
0,90 0,00927 0,04775 0,01974 0,09000
0,91 0,00898 0,04593 0,02076 0,09062
0,92 0,00867 0,04411 0,02180 0,09114
         
0,93 0,00833 0,04229 0,02286 0,09166
0,94 0,00796 0,04047 0,02394 0,09217
0,95 0,00757 0,03865 0,02504 0,09266
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