Sensitivity Factors from FORM method¶
(1)¶
The sensitivity factors indicate the importance on the Hasofer-Lind
reliability index (refer to ) of the value of the parameters used to
define the distribution of the random vector .
Here, the event considered is explicited directly from the limit state
function : this is the classical
structural reliability formulation.
However, if the event is a threshold exceedance, it is useful to
explicit the variable of interest
, evaluated from the model
. In that case, the event considered, associated to
the threshold
has the formulation:
and the limit state function is :
.
is the threshold exceedance probability, defined as:
.
Thus, the FORM sensitivity factors offer a way to rank the importance of
the parameters of the input components with respect to the threshold
exceedance by the quantity of interest
. They can be seen as a
specific sensitivity analysis technique dedicated to the quantity Z around
a particular threshold rather than to its variance.