limited state design methodology (As defined in AS 4676)

Limit State Design uses a load and resistance format, which separates the effects of component strengths and their variability from the effects of external loadings and their uncertainty. Limit states to be considered in the design of overhead lines are—

(a) ultimate strength limit state in which the structure’s or component’s design capacity exceeds the design load; and

(b) serviceability limit state in which the performance of the structure or component under commonly occurring loads or conditions will be satisfactory. Serviceability limit states include vibration, clearance and support deflections. Exceeding the serviceability design load may cause damage to some components.

NOTE: A structure, or part thereof, or component may be designed to fail or undergo high deflections under some loading situations in order to relieve loads on other parts of the structural system. When this occurs, serviceability limit states may not be maintained.