Appendix 3

 ADVANCED PROVISIONS AND CONSIDERATIONS APPLICABLE TO VERY HEAVY AND/OR VERY LARGE CARGO ITEMS

This appendix contains additional advice that may be considered for the stowage and securing of cargo with unusual characteristics, as referenced in chapter 1.8 of this Code and may include items of exceptional mass and/or dimension. However, the listed considerations do not claim to be complete.

 1 Longitudinal tipping

For the securing of large and tall cargo items in longitudinal direction, the balance calculation should also consider longitudinal tipping and meet the following condition:

• F_x⋅ a ≤ b⋅ (m ⋅ g - f_z ⋅ F_z) + CS₁ ⋅ c₁ + CS₂ ⋅ c₂ +...+ CS_n ⋅ c_n [kNm]

• Where:

• F_x, m, g, F_z, CS, n are as explained under 7.2.1 of this annex.

• a is lever-arm of tipping (m) (see figure 18)
• b is lever-arm of stableness (m) (see figure 18)
• c is lever-arm of securing force (m) (see figure 18)

The factor f_Z is obtained by the applicable relation of b/a as shown below:

 2 Rotational inertia of large cargo items

2.1 The algorithm used in 7.2.2 of this annex and section 1 above for defining the tipping moment acting on a distinct cargo item replaces the physical extent of the item by its centre of gravity. The tipping moment is then declared as the determined horizontal force F_x or F_y, multiplied by the vertical distance "a" of this centre of gravity to the edge of the footprint, i.e. the tipping axis of the item. This is sufficiently accurate, as long as the spatial dimensions of the item remain below about 6 metres.

2.2 Larger items, however, will develop a substantial additional tipping moment by their rotational inertia against the rotational acceleration of the ship in rolling or pitching motions. The additional tipping moment is independent from the stowage position of the item in the ship and always positive, i.e. intensifying the tipping impulse. This phenomenon requires additional securing measures and, therefore, should be included in tipping balances for large cargo items by the use of a simple algorithm.

2.3 Transverse tipping balance

2.3.1 For cargo items of width w (measured athwartships) and height h, where (w² + h²) > 50 m², the additional tipping moment k ⋅ J due to rotational inertia of the cargo item should be added to the ordinary tipping moment F_y ⋅ a in the transverse tipping balance.

2.3.2 The appropriate figure of the moment of rotational inertia J should be supplied by the shipper related to the centre of gravity of the item for the plane of transverse tipping. If such information is not available, an estimated figure may be used by:

• J = m ⋅ [tm²] for homogeneous distribution of mass in the item

• J = m ⋅ [tm²] for an item with peripheral concentration of mass.

The reverse angular acceleration k may be taken as [s^-2].

2.4 Longitudinal tipping balance

2.4.1 For cargo items of length l (measured fore and aft) and height h, where (l² + h²) > 50 m², the additional tipping moment k ⋅ J due to rotational inertia of the cargo item should be added to the ordinary tipping moment F_x ⋅ a in the longitudinal tipping balance.

2.4.2 The appropriate figure of the moment of rotational inertia J should be supplied by the shipper related to the centre of gravity of the item for the plane of longitudinal tipping. If such information is not available, an estimated figure may be used by:

• J = m ⋅ [tm²] for homogeneous distribution of mass in the item

• J = m ⋅ [tm²] for an item with peripheral concentration of mass

The reverse angular acceleration k may be taken as [s^-2].

 3 Separate consideration of wind and sea sloshing

3.1 The algorithm used in this annex for defining the horizontal force F_x or F_y, acting on a cargo item stowed on deck, combines horizontal weight components, inertia forces and wind/sloshing forces for reasons of simplification. This is correct for the balance of sliding; however, it is an approximation only for the balance of tipping. Particularly, high deck cargo items with their major wind exposed area well above the centre of gravity should be given a separate compilation of moments from wind forces, sea sloshing forces and gravity/inertia forces in order to get a more realistic tipping moment. The inertia forces strike on the centre of gravity of the cargo item, the sea sloshing strikes on the cargo area not more than 2 m above the weather deck and the wind forces strike on the lateral area of the cargo item exposed to wind.

Example: The figures of the tipping lever "a" relate to a large portal harbour crane shipped on deck of a heavy lift ship. The centres of attack by wind and spray deviate considerably from the centre of gravity. A separate compilation of the longitudinal tipping moment reads:

3.2 The conventionally computed tipping moment would be only:

3.3 The surplus over the conventional tipping moment here is about 6%. The potential additional tipping moment by rotational inertia has not been reflected in this example.

 4 Interpretation of "on deck high"

4.1 The stowage level "on deck high" in table 2 of annex 13 has been positioned at a distance above the water line of about two thirds of the ship's breadth. With extremely large cargo items this level can easily be exceeded. In order to avoid uncertainties in the determination of transverse and longitudinal accelerations in such cases, it is recommended to use the original mathematical model, which has been the basis for acceleration tables in annex 13. This model may easily be programmed, e.g. in a suitable spreadsheet.

4.2 The shown mathematical model is identical to that used in the International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code) (resolution MSC. 5(48)). However, while in the IGC Code the probability level of accelerations refers to the lifetime of a ship of 10⁴ days, annex 13, in order to remain within the scope of practical cargo securing experience, applies a reduction factor of 0.74, corresponding to the 25-day significant wave height in the North Atlantic. Furthermore, the model has been expanded to supply reasonable K-parameters for B/GM-relations less than 7, applicable to ships with exceptional large GM-values.

Mathematical model of the acceleration tables 2 to 4

4.3 The longitudinal, transverse and vertical accelerations acting on a cargo item may be obtained alternatively by the set of formulas as follows:

• a_x = c₁ ⋅ c₂ ⋅ c₃ ⋅ a_x0 ⋅ g [m/s²]
• a_y = c₁ ⋅ c₂ ⋅ c₃ ⋅ a_y0 ⋅ g [m/s²]
• a_z = c₁ ⋅ c₂ ⋅ c₃ ⋅ a_z0 ⋅ g [m/s²]

a_x: longitudinal acceleration (gravity component of pitch included)

a_y: transverse acceleration (gravity component of roll included)

a_z: vertical acceleration (component due to static weight not included)

c₁: correction factor for navigation area, taken as 1.0 worldwide in annex 13

c₂: correction factor for season, taken as 1.0 for whole year in the annex 13

c₃: correction factor for 25 navigation days, taken as 0.6 + 0.1⋅ log1025 = 0.74 in annex 13

• a_x0 = ± a₀ ⋅

• a_y0 = ± a₀ ⋅

• a_z0 = ± a₀ ⋅

therein:

• a₀ = 0.2 ⋅

• A =

• K = R ⋅ , but never less than 1.0

• R= , but never greater than 1.0

L = length between perpendiculars [m]

B = moulded breadth of ship [m]

GM = metacentric height of ship [m]

C_b = block coefficient of ship

x = longitudinal distance from amidships to calculating point, positive forward [m]

z = vertical distance from actual waterline to calculating point, positive upward [m]

v = service speed [knots]

g = gravity acceleration = 9.81 [m/s²]

 5 Structural strength assessment

5.1 Dry cargo ships are typically designed on the assumption that cargo is homogeneously distributed. The maximum permissible surface load is usually specified in the ship's documentation and given in t/m² for all relevant stowage areas, i.e. double bottom (tank top), top of stepped side tanks, 'tween deck pontoons, weather deck and weather deck hatch covers.

5.2 Heavy cargo items tend to produce concentrated strip or point loads rather than homogeneous loads. Then care should be taken that the stress parameters, corresponding to the maximum permissible homogeneous load, are not exceeded by the load induced by the heavy item. The essential parameters for stresses in deck sections, hatch covers and 'tween deck pontoons or panels are shear forces and bending moments. Suitable steel or timber beams or equivalent panel structures should be used to transfer the strip or point load to the primary members of the load-bearing structure.

5.3 Where a loading situation appears to be too complex to be safely examined by manual calculation or where stress parameters obtained by a manual calculation method come close to the applicable limit of the supporting structure, utilization of finite element analysis should be considered.

 6 Weather routeing

6.1 Utilizing weather routeing services may significantly contribute to performing a safe passage. Care should be taken that the engaged service complies with the recommendations laid down in MSC/Circ.1063 on Participation of ships in weather routeing services.

6.2 In case of transporting heavy and/or large cargo items, where safe securing is an essential requirement, the routeing decisions should be oriented to the avoidance of severe ship motions rather than to other criteria, such as swift passage or fuel economy. However, the engagement of a weather routeing service does not eliminate the need for the application of securing measures as required in this annex.

 7 Other considerations

When planning the transport of very heavy and/or very large cargo items on deck of a vessel, particular consideration should be given to:

• .1 the observation of sight line requirements as stipulated in SOLAS regulation V/22, and, in case of non-compliance, the conditions for a temporary exemption by the Flag State Administration;

• .2 the provision of unimpeded radar transmission with due observation of resolution MSC.192(79) on Revised performance standards for radar equipment and SN.1/Circ.271 on Guidelines for the installation of shipborne radar equipment; and

• .3 the provision of visibility of navigations light as required by annex I of International Regulations for Preventing Collisions at Sea and specified in resolution MSC.253(83) on Performance standards for navigation lights, navigation light controllers and associated equipment.