OS-C501

Offshore Standard DNV-OS-C501, November 2013
Sec.8 Safety-, model- and system factors – Page 137
2.5.2 The full set of partial factors is shown in App.E. It shall be used with a characteristic strength defined as
the 2.5% quantile value. These factors depend on the properties described in [2.2.1].
2.6 Partial safety factors for functional and environmental loads as typically defined for risers
2.6.1 If loads are defined as functional and environmental loads as commonly done in offshore applications as
described in Sec.3 [9.3.6], the partial factors in Table 8-4 should be used.
Table 8-4 Partial load effect factors γ F
Limit state F-load effect E-load effect
γ 1) F γ 2) E
ULS 1.1 1.3
FLS 1.0 1.0
NOTES
1) If the functional load effect reduces the combined load effects, γ F shall be taken as 1/1.1.
2) If the environmental load effect reduces the combined load effects, γ E shall be taken as 1/1.3.
Guidance note:
Functional loads are defined as mean loads in Table 8-4.
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2.6.2 The resistance factors applicable to ultimate limit states (ULS) are specified in the Table 8-5 and Table
8-6. The factors are linked to the safety class to account for the consequence of failure.
Table 8-5 Brittle failure type – Partial resistance factor
Safety Class
COV of the strength
COV < 10% 10%-12.5% 12.5%-15%
Low 1.22 1.33 1.49
Normal 1.34 1.53 1.83
High 1.47 1.75 2.29
Table 8-6 Ductile/Plastic failure type – Partial resistance factor
Safety Class
COV of the strength
COV < 10% 10%-12.5% 12.5%-15%
Low 1.11 1.16 1.23
Normal 1.22 1.33 1.49
High 1.34 1.53 1.83
2.6.3 The resistance factors applicable to serviceability limit states (SLS) are specified in the Table 8-7. The
factors are linked to the safety class to account for the consequence of failure.
Table 8-7 SLS – Partial resistance factor
Safety Class
COV of the strength
COV < 10% 10%-12.5% 12.5%-15%
Normal 1.11 1.16 1.23
High 1.22 1.33 1.49
2.7 Partial safety factors for functional and environmental loads as typically defined for TLPs
2.7.1 If loads are defined as functional and environmental loads as commonly done in offshore applications
for Tension Leg Platforms (TLPs) as described in Offshore Standard DNV-OS-C105 “Structural Design of
TLPS”, the partial factors in Table 8-8 should be used.
Table 8-8 Partial load effect factors γ F
Load categories
Combination of design loads Permanent and functional loads Environmental loads Deformation loads
a) 1.2 * 0.7 1.0
b) 1.0 1.3 1.0
* ) If the load is not well defined e.g. masses or functional loads with great uncertainty, possible overfilling of tanks etc.
the coefficient should be increased to 1.3.
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