Offshore Structure Loads and Strength - Offshore Structures: Design, Construction and Maintenance - page 41

blocks, hooks and others, F H is the horizontal load due to offlead and side-lead
and f is a dynamic coefficient that should be taken as 2.0 for sea lifts and 1.3 for
platform lifts.

Crane Working with Wind

F cw = F G + fF L + F H +

F W (2.4)

where F cw is the crane lateral load due to wind, F G , F L , F H and f are as above,
F W is the operating wind action and f should be taken as 2.0 for sea lifts and 1.3
for platform lifts for a maximum crane operating wind.

Crane at Rest (Not Working), Extreme Wind

F cr = F G + F W,max (2.5)

where F cr is the crane load at rest, F G is as above and F W,max is the extreme
wind action.
The action factors used with each of the above should be those for normal
operating conditions.
For the crane working in calm conditions and the crane working at maximum
operating wind conditions, F L should be selected to check the lifted load
applicable to both maximum and minimum crane radius, for sea and platform
lifts.
For the crane working at maximum operating wind conditions and the crane
at rest in extreme wind conditions, the most onerous wind directions should be
checked.
It should be demonstrated that the crane pedestal and its components are
designed to safely resist the forces and moments from the most onerous loading
condition applicable to the prevailing sea state together with associated offlead
and side-lead forces. These values should be obtained from the crane manufacturer,
and the angles used should not be less than the following:

Offlead angle: 6 °

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Side-lead angle: 3 °

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The crane support structures should be designed so that their failure load
exceeds the collapse capacity of the crane.
The crane manufacturer s failure curves, for all crane conditions, should be

used to determine the worst loading on the pedestal. It should be assumed that
the maximum lower bound failure moment of the weakest component will place
an upper bound on the forces and moments to which the pedestal can be subjected.
The design moment for the crane failure condition should be taken as the lower
bound failure moment described above, multiplied by a safety factor of 1.3.
It is not normal practice for the support structure of offshore cranes to be
subject to a dynamic analysis. The process of fatigue design incorporates an

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