Section 1 General

1.1.1 These Rules apply to dock gates, as defined in Pt 2, Ch 2, 1.3 Types of dock gate. Although the Rules are, in general, for steel floating docks of all welded construction, other materials and design configurations will be specially considered.

1.1.2 The following aspects are not covered by these Rules:

1. connections to the dock walls/entrance;
2. slots for sliding/rolling dock gates;
3. stability aspects;
4. the dock structure supporting the dock gate;
5. equipment and machinery for operating the dock gate;
6. electrical and hydraulic systems;
7. portable equipment, staging or temporary supports; and
8. mooring lines or dock side winches.

1.2.1 Design life. The design life is to be defined by the designer, however, it is recommended that the design life be at least 60 years.

1.2.2 Water density. The water density is to be specified by the designer based on the intended operation of the dock gate. Where the water density is not known, it is to be taken as 1,025 t/m³.

1.2.3 The global strength assessment is to be carried out on the basis of net scantlings, see Pt 2, Ch 2, 4.3 Net scantling approach.

1.2.4 Measures such as coatings and cathodic protection are to be employed in accordance with the requirements of Pt 3, Ch 2, 3 Corrosion protection of the Rules and Regulations for the Classification of Ships, July 2022.

1.3.1 Floating dock gate. A floating dock gate consists of a large floating steel box which is ballasted to seat the dock gate in the opening of the dock. The dock gate is re-floated by de-ballasting and is then towed clear of the entrance to the dry dock. Floating dock gates can also be hinged at the side of the dock. See Figure 2.1.1 Floating dock gate.

1.3.2 Sliding and rolling dock gate. A floating or sliding dock gate consists of a narrow rectangular box which is opened by moving the gate into a recess in the side of the entrance. The dock gate is lightly ballasted so that it can be moved on a track or slid into the recess. See Figure 2.1.2 Rolling or sliding dock gate.

1.3.3 Mitre gates. Mitre gates are a pair of hinged gates which form a ‘V’ shape with the greater hydrostatic pressure being on the outside of the V and hence holding the gates closed. See Figure 2.1.3 Mitre gate.

1.3.4 Flap gates. Flap gates are hinged at the bottom in way of the entrance sill of a dock and are opened by being lowered down into the water so that they lie flat on the seabed below the entrance sill. Buoyancy tanks are often used in conjunction with hydraulic rams or winches to lower the gate. See Figure 2.1.4 Flap gate.

1.4.1 These Rules relate to the construction of welded steel dock gates.

1.4.2 The materials used in the construction of the dock gate 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.

1.4.3 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.

1.4.4 For the determination of the hull girder section modulus, where higher tensile steel is used, a higher tensile steel factor, k_L, is given in Pt 2, Ch 2, 1.4 Materials 1.4.4.

1.4.6 The material grade requirements for hull structural members are to be as required by Pt 3, Ch 2, 2 Fracture control of the Rules and Regulations for the Classification of Ships, July 2022, but in no case are to be taken less than Grade D.

1.4.7 Consideration will be given to the use of bolted connections within the dock gate main structure. Such bolted connections are to comply with the requirements of Eurocode 3, Part 1-8. All bolts used for primary connections are to be high strength friction grip bolts. For normal operating load scenarios, the bolts are to be designed to be non-slip. Under extreme loading conditions (including seismic), the bolts can be designed on the basis of their ultimate shear strength.

1.5.1 A document describing the full operational cycle of the dock gate including repair and maintenance is to be submitted.

1.5.2 The full range of environmental operating conditions is to be defined, including:

• Highest and lowest astronomical tides (HAT and LAT) for the site location and the associated return period.
• Maximum and operational significant wave heights and periods and directions associated with a 60-year return period for the site. Information is also to include the effects of waves from passing marine craft.
• Maximum current speeds and directions at site including the effects of ships' propulsion units.
• Seabed conditions and likelihood of silting in vicinity of site.
• The anticipated effects of passing marine craft at site.
• For areas subject to sub-zero temperatures the lowest mean daily average temperature (MDAT) for the location is to be submitted.
• Extreme snow and ice loading.
• Foreseeable accident events are to be defined including collision, grounding, and degradation
• Seismic conditions where appropriate.

1.5.3 Operational data is to be provided including;

• Vehicle loading data on ramps and decks.
• Design uniformly distributed loadings.
• Loads imposed by tugs or berthing.
• Passenger/pedestrian loadings.
• Docking arrangements.
• Ballasting and de-ballasting sequence where appropriate.
• Design air pressures where compressed air is used for ballasting or de-ballasting operations.
• Any other loadings not specified above.

1.5.4 The following plans are to be submitted for approval:

• General arrangement plan.
• Section at mid-length.
• Structural plans of tank boundaries (if any).
• Structural plan of shell including bottom of dock gate or pontoons (if applicable).
• Structural plans of bulkheads and pillars.
• Structural plans of deck/walkway/roadway.
• Structural plans of ramps.
• Welding and construction details.
• Material grades.
• Mooring and towing attachments and seats.
• Sealing arrangement.
• Air pipes and discharges.
• Corrosion prevention arrangements.
• Hydrostatic curves.

1.5.5 The critical joints and critical weld connections are to be shown on the structural plans.

1.6.1  In addition to the requirements of Pt 2, Ch 2, 1.5 Plans and information required, the following is to be submitted:

1. Dock gate lightweight.
2. The total lightweight should be sub-divided into weights of:
   1. pontoon or dock gate or walls;
   2. wing walls above pontoon/dock gate dock level;
   3. supporting blocks;
   4. machinery and outfit;
   5. end aprons/working platforms; and
   6. deck roadway surfacing where appropriate.
3. Depth of water in dock.
4. Proposed distance of air pipe openings below the safety deck inside tanks and/or the pontoon deck in centre tanks, as applicable.
5. 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.
6. 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.
7. Section modulus calculation.
8. Global strength calculations.
9. NDE plan showing the critical joints and critical welds.