The user-defined distribution allows the user to directly specify a custom distribution of any form, which is computed dynamically during the simulation. To define the failure distribution, you specify the Fraction Failed (as an expression or a link.)
The Fraction Failed should be specified as a dimensionless value. Typically, it will be specified as a function of the elapsed time (Etime). It should always be greater than or equal to 0 and less than or equal to 1, and can never decrease as a function of time.
Note: The Effective
Time (for outer barrier failure modes) and the Start Time (for inner
barrier failure modes) is grayed out for user-defined distributions, and any
delays or modifications should be directly incorporated into the definition of
the Fraction Failed.
When a user-defined distribution is used for an inner barrier failure mode which is linked to the outer barrier, the distribution is computed and saved starting from the beginning of the simulation, and then used at the appropriate time. For example, suppose that the user-defined distribution was specified as a function of Etime such that the inner barrier(s) failed in such a way that the Fraction Failed was equal to 1 at Etime = 10 years. Suppose further that the inner barrier failure was linked to the outer barrier failure, and the outer barrier failed instantaneously at 25 years. In this case, GoldSim would compute and save the failure distribution, but not apply it until 25 years (i.e., Fraction Failed would be equal to 0 at 25 years, and 1 at 35 years).