OS-C501

Offshore Standard DNV-OS-C501, November 2013
Sec.8 Safety-, model- and system factors – Page 138
Guidance note:
Functional loads are defined as mean loads in Table 8-8.
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2.7.2 The loads shall be combined in the most unfavourable way, provided that the combination is physically
feasible and permitted according to load specifications. For permanent loads, a load factor of 1.0 in load
combination a) shall be used where it gives the most unfavourable response. Other considerations for the partial
coefficients are given in DNV-OS-C101.
2.7.3 The resistance factors applicable to ultimate limit states (ULS) are specified in the Table 8-9 and Table
8-10. The factors are linked to the safety class to account for the consequence of failure.
Table 8-9 Brittle failure type – Partial resistance factor
Safety Class
COV of the strength
COV < 10% 10%-12.5% 12.5%-15%
Low 1.35 1.46 1.63
Normal 1.48 1.68 2.01
High 1.62 1.93 2.51
Table 8-10 Ductile/Plastic failure type – Partial resistance factor
Safety Class
COV of the strength
COV < 10% 10%-12.5% 12.5%-15%
Low 1.22 1.27 1.35
Normal 1.35 1.46 1.63
High 1.48 1.68 2.01
3 Model factors
3.1 General
3.1.1 The following two types of model factors are defined in this standard:
— load model factors, designated by γ Sd
— resistance model factors, designated by γ Rd .
3.2 Load model factors
3.2.1 Load model factors γ Sd account for inaccuracies, idealisations, and biases in the engineering model used
for representation of the real response of the structure, e.g. simplifications in the transfer function (see Sec.9
[1.4]). Effects of geometric tolerances shall also be included in the load model factor. The factor is treated here
as a deterministic parameter.
3.2.2 Details about the load model factor are given in Sec.9 [12]. The factor shall make up for uncertainties
and inaccuracies in the transfer function, the analysis methods, and dynamic effects.
3.3 Resistance model factors
3.3.1 Resistance model factors γ Rd account for differences between true and predicted resistance values given
by the failure criterion.
3.3.2 Model factors shall be used for each failure criteria. The factors are given in Sec.6 for each failure
criterion. A summary is given in Table 8-11.
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