Fragility of transmission tower-line system subjected to concurrent wind and ice accretion

Abstract

Severe ice accretion and its concurrent wind load could cause failure of overhead transmission system or reduce its capacity. We proposed a simple-to-use procedure to assess the capacity curve and fragility curve or surface of the lattice transmission tower-line system subjected to the concurrent ice and wind loads. The procedure is based on nonlinear static pushover analysis (NSPA) and considers the influence of ice-coated cables and towers. The comparison of the NSPA curve to the capacity curves obtained from the incremental dynamic analysis (IDA) allowed us to suggest the use of the ice accretion thickness and 3-s gust mean wind speed as the intensity measures for the fragility surface. Since the NSPA does not account for uncertain spatiotemporal varying winds, we incorporated this effect in the proposed procedure by using the statistics of a modelling factor or error defined as the ratio of the IDA curves to the NSPA curve. We assessed the effects of the loading path, wind direction, and partial correlation of a material property or geometrical variable on the capacity curve and fragility surface. The use of the fragility surface to assess the reliability of the tower-line system under a scenario icing event was illustrated.