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9.6.4.5 Self Weight of Structural Members
The self-weight of the helideck supported by the member concerned should be included with the appropriate load factor. The self-weight is the weight of decking, stiffeners, support structure and accessories supported by the member or substructure being considered.
The designer is recommended to make a conservative estimate of this load at the start of the design process and to then confirm the dead load at the end of the detail design to verify the accuracy of the design.
9.6.4.6 Environmental Loads
Helidecks on mobile installations must be designed for gravity and inertial forces due to the unit’s motions and accelerations. Additionally, sea pressure and green sea loads on the support structure may need to be considered.
The designer should make reference to the loading criteria used for the design of the vessel to ensure that all loading resulting from vessel motions and external wave loading will be fully allowed for in the design of the helideck.
The designer should take full account of wind loading on the helideck structure. Wind loading cases should include pressure, lift and side loads, helicopter landing side loads from Section 9.6.4.4 plus wind load at the limiting wind speed for helicopter operation and, for the helicopter on deck case, side loads for deck and helicopter at the maximum environmental wind velocity considered. Wind velocity should be taken as the 3-second gust at helideck elevation above sea level. Wind load may be determined in accordance with the guidelines set out in BS 6399 Part 1 Wind Loads [Ref: 58].
9.7 HELIDECK FRICTION SURFACE AND LANDING NETS
9.7.1 Friction Surface
An adequate non-slip surface should be provided for the whole of the helideck to ensure the safe movements of both helicopters and personnel. The designer should therefore properly consider the helideck surface materials of construction and specify the correct and most appropriate friction surface for the helideck as a whole and in particular the safe landing area, irrespective of whether a landing net will be fitted.
9.7.2 Main References
CAP 437, Section 3.8.
9.7.3 Design Considerations
All materials, coverings or coatings used to provide a non-skid surface should be structurally fastened to the helideck or bonded with an adhesive agent that is not chemically altered in the presence of fuel, oil and the effects of guano. This includes both specialist paint systems used with aggregates and pre-formed / coloured non-slip tiling systems.
(Photo courtesy of John Burt Associates Limited)
In the case of extruded aluminium construction an adequate non-slip profile (effective in all directions) should be specified as part of the surface structure. Alternatively, a high friction paint system should be specified.
It should be noted that where new, unpainted aluminium helidecks are exposed to prolonged periods of strong sunlight high surface temperatures are likely to be experienced. It is recommended that a high friction paint system be applied to mitigate these effects.
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