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B: Load Categories [Table of Contents] Sec.5: Global Performance

DNV-OS-C105 Structural Design of TLPS (LRFD method)

[-] Sec.4: Design Loads
[-] B: Load Categories
[-] B100: General

Sec.4
B 100   General

Sec.4 B
101   All relevant loads that may influence the safety of the structure or its parts from commencement of fabrication to permanent decommissioning should be considered in design. The different loads are defined in DNV-OS-C101.

Sec.4 B
102   For the deck and hull of the TLP, the loads are similar to those described in DNV-OS-C103 for TLPs similar to column stabilised units. TLPs similar to deep draught floaters are to be designed with loads as given in DNV-OS-C106. Loads are described in the above with exception of the tendon loads (inclusive potential ringing and springing effects).

Sec.4 B
103   In relation to determination of environmental conditions and loads, see DNV-RP-C205 and DNV-OS-C501 for composites.

Sec.4 B
104   The wave loads on the tendons may be described as recommended in DNV-RP-C205 for slender structures with significant motions.

Sec.4 B
105   The disturbance of wave kinematics from hull (columns and pontoons) in relation to the riser system and tendons shall be accounted for if it is of importance.

Sec.4 B
106   The earthquake loads at the foundation of the tendons are described in DNV-OS-C101.


Sec.4 B
107   The following loads should be considered:
—permanent loads
—variable functional loads
—environmental loads
—deformation loads
—accidental loads.


Sec.4 B
108   For preliminary design stages it is recommended that "contingency factors" are applied in relation to permanent loads to reflect uncertainties in load estimates and centres of gravity.

Sec.4 B
109   "Contingency factors" should also be considered for early design stages in relation to variable functional loads, especially for minimum facilities TLPs (e.g. TLWP and Mini TLP).

Sec.4 B
110   The environmental loads are summarised as:
—wind loads
—mean (sustained) wind
—dynamic (gust) wind
—wave and current loads
—loads on slender members
—loads induced by TLP motions
—slamming and shock pressure
—wave diffraction and radiation
—mean drift forces
—higher order non-linear wave loads (slowly varying, ringing and springing)
—wave enhancement
—vortex shedding effects
—marine growth
—snow and ice accumulation
—direct ice loads (icebergs and ice flows)
—earthquake
—tidal and storm surge effects
—effects from sand/marine growth getting into the connectors or the tendon body
—resistance to sunlight during transport, storage and operation if above the water.


Sec.4 B
111   Resistance of the tendon (i.e. for "dry lock-off" systems) to fire on or near the platform shall be evaluated.
B: Load Categories [Table of Contents] Sec.5: Global Performance