2.0 RBD Methodology

This section describes a Reliability-Based Design (RBD) methodology for transmission and distribution line structures. The RBD approach is calibrated to yield average reliability levels consistent with years of history and practice with existing deterministic design approaches. Therefore, on the average, designs will be nearly equivalent to what engineers have used. This methodology strives to correct the problem of inconsistent reliabilities among different material types. Minimum reliability levels are recommended for different grades of construction. Simply selecting different return periods in designing the line quantifiably varies reliability levels. The method uses one set of load and load factors regardless of the material type. The strength reduction factors are a function of material type. The equations are based on initial strength before material degradation occurs.