The Failure Frequency of Systems with Dependent Components

The conventional approach to determining system failure frequency does not allow for dependent components. A novel approach presented here shows very clearly which information is needed to treat the case of dependence. The information is more complicated than that needed for system availability determination, yet it is of the same type, viz, joint probabilities or higher moments of joint binary processes. The main result is: System failure frequency can be found as the limiting value (for Δt → 0) of the expectation of the product of the negated fault tree output at t and the usual output at t + Δt, all divided by Δt.