Offshore Structure Loads and Strength - Offshore Structures: Design, Construction and Maintenance - page 35

Safety Net Arms and Framing
Safety nets for personnel protection should be installed around the landing area
except where structural protection exists. The netting used should be flexible,
with the inboard edge fastened level with, or just below, the edge of the helicopter
landing deck. The net itself should extend at least 1.5 m in the horizontal plane
and be arranged so that the outboard edge is slightly above the level of the landing
area, but not by more than 0.25 m, so that it has an upward and outward slope of at
least 10 . The supporting structure associated with the safety net should be cap-

able of withstanding, without damage, a 75 kg weight being dropped from a
height of 1 m onto an area of 0.25 m 2 .
The entire helideck, including any separate parking or runoff area, should be
designed to resist an imposed load equal to the MTOM of the helicopter. This
load should be distributed between all the undercarriages of the helicopter. It
should be applied in any position on the helicopter platform so as to produce
the most severe loading condition for each element considered.
The values for these overall superimposed loads, dead loads, and wind loads
should be considered to act in combination with the dynamic load impact, as
discussed above. Consideration should also be given to the additional wind
loading from any parked or secured helicopter.
Based on the American Petroleum Institute (API) RP2L design for heliports,
the flight deck, stiffeners and supporting structure should be designed to
withstand the helicopter landing load encountered during exceptionally hard
landing after power failure while hovering. Examples of helicopter parameters
that should be obtained are shown in Table 2.11 and it is recommended that para-
meters similar to those given in the table be obtained from the manufacturer of
any helicopter considered in the helideck design.
The maximum contact area per landing gear used to design deck plate
bending and shear should conform to the manufacturer

°

s values given in
Table 2.11 . For multiwheeled landing gear, the value of the contact area is
the sum of the areas for each wheel. The contact area for float or skid landing
gear is the area of the float or skid around each support strut.
The load distribution per landing gear, in terms of percentage of gross
weight, is given in Table 2.11 .
The design landing load is the landing gear load based on a percent of a
helicopter

'

s gross weight times an impact factor of 1.5. For percentages and
helicopter gross weight, see Table 2.11 .

'

Design Load Conditions
The heliport should be designed for at least the following combinations of
design loads:

Dead load plus live load. ●

Dead load plus design landing load. If icing conditions are prevalent during
normal helicopter operations, superposition of an appropriate live load
should be considered.

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