Clasification Society Rulefinder 2020 - Version 9.33 - Fix
Common Structural Rules - Common Structural Rules for Bulk Carriers and Oil Tankers, January 2019 - Part 1 General Hull Requirements - Chapter 4 Loads - Section 3 Ship Motions and Accelerations - 2 Ship Motions and Accelerations

2 Ship Motions and Accelerations

2.1 Ship motions

2.1.1 Roll motion

The roll period Tθ, in s, to be taken as:

The roll angle θ, in deg, to be taken as:

θ =

where:

fp : Coefficient to be taken as:

fp = fps for strength assessment.
fp = ffa (0.23 - 4fT B x10–4) for fatigue assessment.

fBK: To be taken as:

fBK = 1.2 for ships without bilge keel.
fBK = 1.0 for ships with bilge keel.

kr: Roll radius of gyration, in m, in the considered loading condition. The values in Table 1 or Table 2 are to be adopted.

GM: Metacentric height, in m, in the considered loading condition. The values in Table 1 or Table 2 are to be adopted.

Table 1: kr and GM values for oil tankers

Loading condition (1) (2) TLC kr GM
Full load condition TSC 0.35B 0.12B
Optional conditions that have a draught greater than 0.9TSC Actual draught but ≥ 0.9TSC 0.35B 0.12B
Partial load condition ≤ 0.6TSC 0.40B 0.24B
Ballast condition TBAL 0.45B 0.33B
(1) For optional loading conditions or gale/emergency ballast conditions with draught between 0.6TSC and 0.9TSC, the values of kr and GM, unless provided in the loading manual, are to be obtained by linear interpolation between the optional condition at 0.9TSC and the partial load condition at 0.6TSC based on the actual draught.
(2) For flooded loading conditions, the values of kr and GM, unless provided in the loading manual, are to be taken as those for the full load condition.

Table 2: kr and GM values for bulk carriers

Loading condition (1) (2) (4) Application TLC kr GM
Full load condition Homogeneous loading All bulk carriers TSC 0.35B 0.12B
Alternate heavy cargo BC-A 0.40B 0.20B
Alternate light cargo BC-A 0.35B 0.12B
Homogeneous heavy cargo BC-B, BC-A 0.42B 0.25B
Steel coil loading (3) All bulk carriers designated for the carriage of steel products 0.42B 0.25B
Heavy ballast condition All bulk carriers TBAL-H 0.40B 0.25B
Normal ballast condition All bulk carriers TBAL 0.45B 0.33B
(1) For Multi-port (MP) loading conditions with draught greater than or equal to 0.9TSC, the values of kr and GM, unless provided in the loading manual, are to be taken as those from the most appropriate full load condition.
For Multi-port (MP) loading conditions with draught between TBAL-H and 0.9TSC, the values of kr and GM, unless provided in the loading manual, are to be obtained by linear interpolation, based on the draught, between the heavy ballast condition and the most appropriate full load condition.
For Multi-port (MP) loading conditions with a draught below TBAL-H, the values of kr and GM for the heavy ballast condition are to be used.
(2) For flooded loading conditions, the values of kr and GM, unless provided in the loading manual, are to be taken as those for the full load condition.
(3) When steel coil loading condition is provided by the designer according to Ch 1, Sec 2, [3.6] in the loading manual, this condition is to be assessed with draught, kr and GM values given in this table.
(4) Block Loading conditions are to be assessed with draught, kr and GM values given in this table for Homogeneous heavy cargo loading condition.

2.1.2 Pitch motion

The pitch period Tϕ, in s, is to be taken as:

where:

λϕ = 0.6 (1 + fT) L

The pitch angle ϕ, in deg, is to be taken as:

where:

fp: Coefficient to be taken as:

fp = fps for strength assessment.

fp = ffa [(0.27 – 0.02fT) – (13 – 5fT) L × 10–5] for fatigue assessment.

2.2 Ship accelerations at the centre of gravity

2.2.1 Surge acceleration

The longitudinal acceleration due to surge, in m/s2, is to be taken as:

asurge = 0.2 fp a0 g

where:

fp: Coefficient to be taken as:

fp = fps for strength assessment.

fp = ffa [0.27 – (15 + 4 fT) L × 10–5] for fatigue assessment.

2.2.2 Sway acceleration

The transverse acceleration due to sway, in m/s2, is to be taken as:

asway = 0.3 fp a0 g

where:

fp: Coefficient to be taken as:

fp = fps for strength assessment.

fp = ffa [0.24 – (6 – 2 fT) B × 10–4] for fatigue assessment.

2.2.3 Heave acceleration

The vertical acceleration due to heave, in m/s2, is to be taken as:

aheave = fp a0 g

where:

fp: Coefficient to be taken as:

fp = fps for strength assessment.

fp = ffa [(0.27 + 0.02fT) – 17L × 10–5] for fatigue assessment.

2.2.4 Roll acceleration

The roll acceleration, aroll, in rad/s2, is to be taken as:

where:

θ: Roll angle using fp equal to 1.0.

fp: Coefficient to be taken as:

fp = fps for strength assessment.

fp = ffa [0.23 – 4 fT B × 10–4] for fatigue assessment.

2.2.5 Pitch acceleration

The pitch acceleration, apitch, in rad/s2, is to be taken as:

apitch =

where:

ϕ: Pitch angle using fp equal to 1.0.

fp: Coefficient to be taken as:

fp = fps for strength assessment.

fp = ffa [0.28 – (5 + 6 fT) L × 10–5] for fatigue assessment.

Parent topic: Section 3 Ship Motions and Accelerations
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