OS-C501

Offshore Standard DNV-OS-C501, November 2013
Sec.8 Safety-, model- and system factors – Page 139
Table 8-11 Summary of model factors
Failure Criterion Model factors γ Rd Reference
Fibre Failure 1.0 or γ A Sec.6 [3.2.2]
Matrix Cracking 1.0-1.15 Sec.6 [4.1]-[4.4]
Delamination 1.0-2.0 Sec.6 [5]
Yielding 1.0 Sec.6 [6]
Ultimate failure of orthotropic homogenous materials 1.25 Sec.6 [7]
Buckling Same range as all other criteria. Sec.6 [8]
Displacements 1.0 Sec.6 [9]
Stress Rupture 0.1-1.0 Sec.6 [10.4]
Fatigue 0.1-1.0 Sec.6 [11.3]
4 System effect factor
4.1 General
4.1.1 The safety factors are given for the entire system. Depending on how the components are connected to
form a system, the target probability of failure for individual components may need to be lower than the target
probability of failure of the entire system.
Guidance note:
E.g. In the case of a pipeline system, the failure of one pipe component (i.e. plain pipe or end connector) is equivalent
to the failure of the entire system. This is a chain effect. As a consequence, the target safety of individual components
should be higher than the target safety of the entire system, in order to achieve the overall target safety.
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4.1.2 In order to take this system effect into account, a system effect factor γ S shall be introduced. If the system
effect is not relevant, γ S = 1.0. Otherwise a system factor shall be documented. A value of γ S = 1.10 can be used
as a first approach.
4.1.3 In some cases a system may consist of parallel components that support each other and provide
redundancy, even if one component fails. In that case a system factor smaller than 1 may be used if it can be
based on a thorough structural reliability analysis.
5 Factors for static and dynamic fatigue analysis
5.1
5.1.1 Table 8-12 shows the factors γ fat shall be used for the prediction of failure due to cyclic fatigue or due to
long term static loads. The factors shall be used with the failure criteria in Sec.6 [10] and Sec.6 [11].
Table 8-12 Factor for fatigue calculations γ fat
Safety class
Low Normal High
15 30 50
DET NORSKE VERITAS AS