Offshore Structure Loads and Strength - Offshore Structures: Design, Construction and Maintenance - page 31

TABLE 2.8 Maximum Vertical Deflection Based on ISO 9001

Structural Element Δ Δ

max 2

Floor beams L /200 L /350

Cantilever beams L /100 L /150

Deck plate 2 t or b /150

Note: L is the span, t is the deck thickness and b is the stiffener spacing.

TABLE 2.9 Limiting Values for Vertical Deflection Based on LRFD

Structure Member Δ Δ

max 2

Deck beams L /200 L /300

Deck beams supporting plaster or other
brittle finish or nonflexible partitions

L /250 L /350

Note: L is the beam span. For cantilevers, L is twice the projecting length of the cantilever.

not exceed 0.2% of the total height of the topside structure. Limits can be
defined to limit pipe stresses and to avoid riser or conductor overstress or
failure. Some designers allow higher deflections for structural elements where
serviceability is not compromised by deflection.

2.2.5 Helicopter Landing Loads
The maximum dynamic local actions from an emergency landing may be deter-
mined from the collapse load of the landing gear. This should be obtained from
the helicopter

s manufacturer.
Alternatively, default values may be used for design by considering an
appropriate distribution of the total impact load of 2.5 times the maximum
take-off weight (MTOW).
The local loads used in design should correspond to the configuration of the
landing gear. A single main rotor helicopter may be assumed to land simulta-
neously on its two main undercarriages or skids. A tandem main rotor helicopter
may be assumed to land on the wheels of all main undercarriages simulta-
neously. For a single main rotor helicopter, the total loads imposed on the struc-
ture should be taken as concentrated loads on the undercarriage centers of the
specific helicopter divided equally between the two main undercarriages. For
tandem main rotor helicopters, the total loads imposed on the structure should
be taken as concentrated loads on the undercarriage centers of the specific

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