Section 1 General

1.1.1 These Rules apply to Caisson and Pontoon type steel floating docks, as defined in Pt 2, Ch 1, 1.2 General design 1.2.1. Although the Rules are, in general, for steel floating docks of all welded construction, other materials and design configurations will be specially considered.

1.2.1 These Rules apply directly to floating docks of the following types:

1. Caisson type, in which the bottom caisson and both wing walls are continuous and inseparable.

2. Pontoon type, in which the wing walls are continuous and the bottom is formed of non-continuous pontoons. The pontoons may be either permanently attached to the wing walls or may be detachable.

1.3.1 The materials used in the construction of the floating dock are to be manufactured and tested in accordance with the requirements of the Rules for the Manufacture, Testing and Certification of Materials, July 2022. Materials for which provision is not made therein may be accepted, provided that they comply with an approved specification and such tests as may be considered necessary.

1.3.2 Steel having a specified minimum yield stress of 235 N/mm² is regarded as mild steel. Steel having a higher specified minimum yield stress is regarded as higher tensile steel.

1.3.3 The local scantling requirements of higher tensile steel plating, longitudinals, stiffeners and girders may be based on a k factor determined as follows:

or 0,66, whichever is the greater,

where

σ_o = specified minimum yield stress in N/mm².

1.3.5 For the application of the requirements of Pt 2, Ch 1, 1.3 Material 1.3.3 and Pt 2, Ch 1, 1.3 Material 1.3.4, special consideration will be given to steel where σ_o ≥ 355 N/mm².

1.3.6 Where higher tensile steel is used in areas which are subject to fatigue loading, and in particular for floating docks intended to undertake an ocean tow, the structural details may be required to be verified using fatigue design assessment methods.

1.4.1 The scantlings of structural members may also be determined using direct calculations. In such a case, the assumptions made, together with the calculations are to be submitted for approval. Alternative arrangements which are proposed as equivalent to these Rules, will also be considered.

1.5.1 The following plans are to be submitted for approval:

• General arrangement plan.
• Section at mid-length.
• Structural plan of wing walls, top deck, safety deck and, for pontoon type docks, the plating across the base of the wing walls in way of the pontoon gaps.
• Structural plan of bottom caisson or pontoons.
• Fresh water and fuel oil tanks.
• Hydrostatic curves.

1.6.1 In addition to the requirements of Pt 2, Ch 1, 1.5 Plans required, the information related to the operating site and method of dock securing, are to be submitted together with the following:

1. Required lifting capacity.

2. Length of shortest contemplated ship having a docking weight equal to the required lifting capacity. Special consideration may be given to the use of a ship length greater than that described, see also Pt 2, Ch 1, 3.7 Special provision 3.7.1.

3. The associated maximum draught of the vessel when entering the dock, also the maximum associated dock submergence draught.

4. Dock lightweight.

   The total lightweight should be sub-divided into weights of:

   1. pontoon or caisson;

   2. wing walls above pontoon/caisson dock level;

   3. supporting blocks;

   4. cranes;

   5. machinery and outfit;

   6. end aprons/working platforms.

5. Depth of rest water.

6. Depth of keel and side blocks.

7. Proposed distance of air pipe openings below the safety deck in side tanks and/or the pontoon/caisson deck in centre tanks, as applicable.

8. The hydrostatic head assumed for the design of boundary bulkheads separating adjacent ballast tanks, to be taken as the maximum allowable difference between the filling levels of adjacent ballast tanks. This head should be included in the dock operating instructions. If not specified, it will be taken as 3,5 m.

9. The hydrostatic head obtained from Hydrostatic Curves to be used for structural design of dock boundary bulkheads and internal bulkheads which separate a ballast tank from a dry space.

10. Section modulus calculation.

11. Full details of the type and proposed arrangement of deflection monitoring equipment.

12. Details of the mooring attachments to the dock structure.

1.7.1 The freeboard to the pontoon deck at the centreline of the dock when supporting a ship having a displacement equal to the lifting capacity is to be not less than 300 mm, see Pt 2, Ch 1, 2.1 General 2.1.1. When the pontoon deck at the inner wing walls is lower than at the centreline, the freeboard to the pontoon deck at the inner wing walls is to be not less than 75 mm and the freeboard at the centreline is to be not less than 300 mm.

1.7.2 The freeboard requirements within Pt 2, Ch 1, 1.7 Freeboard 1.7.1 assume the travelling crane(s) are positioned so as to give level trim. The freeboard at level trim may be required to be increased such that when the travelling crane(s) are moved to the forward end or to the after end of the dock, the pontoon deck is not submerged. The freeboard limits within Pt 2, Ch 1, 1.7 Freeboard 1.7.1 assume the floating dock is to be operated in sheltered waters. For other areas of operation it is recommended that they are suitably increased.

1.8.1 A stability information book is to be prepared by the Builder indicating satisfactory metacentric height (GM) for the following conditions of submergence:

1. full dock submergence;

2. the submergence draught to the top of keel block assuming full weight of the docked ship supported on blocks.

1.8.2 Whilst the responsibility for the approval of the stability aspects will rest with the National Administration involved, it is recommended that the combined GM of the dock and the ship in the condition indicated in see Pt 2, Ch 1, 1.8 Stability 1.8.1.(b) is not less than 1,0 m.

1.8.3 For operating sites exposed to wind heeling moments, these effects should be taken into account. See also Pt 1, Ch 2, 1.1 General 1.1.8.

1.9.1 The class of a floating dock will be assigned after it has reached its port of operation and been subjected to a satisfactory General Examination.

1.9.2 Where it is intended that the dock be towed at sea from its port of construction to port of operation or from one port of operation to another, the aspects specified below will need to be investigated, it is recommended that such aspects be considered at as early a stage as possible and Lloyd’s Register (hereinafter referred to as ‘LR’) be consulted on the requirements for issuing of a ‘Fitness to be Towed Certificate’ (Form 1694):

1. The longitudinal strength is to be sufficient to accommodate the design voyage wave bending moment in association with the Rule stress as given in Pt 2, Ch 1, 3.5 Bending moment 3.5.6. The design voyage wave bending moment will be based on the following information which is to be submitted for consideration:

   1. draught in towage condition;

   2. towage route;

   3. departure date.

   In order to minimize the design voyage wave bending moment, it is recommended that the delivery voyage be undertaken as close to the light draught as possible.

2. Particular attention should be given to the buckling capability of transversely framed bottom structure when the dock is subjected to wave induced hogging moments, since this part of the structure will not normally experience longitudinal compressive loading during floating dock operations.

3. The removal of aprons/working platforms.

4. The securing arrangements of travelling crane(s) and items carried on the pontoon deck.

1.10.1 Where plating thicknesses as determined by the Rules are required to be rounded, then this should be carried out to the nearest half millimetre, with thicknesses 0,75 mm and 0,25 mm being rounded up.

For example,

• for 10,75 ≤ t < 11,25 mm, the Rule required thickness is 11,0 mm;
• for 11,25 ≤ t < 11,75 mm, the Rule required thickness is 11,5 mm.