New model of a thunderstorm downburst and its effect on structures

Abstract

Recent history has shown that downburst thunderstorm can be devastating especially for transmission lines composed of towers relied by an electric cable with numerous reported failures of these structures. The literature is very active in the domain of downburst but failed until now to produce a model that predicts the structural response to downburst solicitation. This paper proposes a new approach of downburst modelling based on physical thought and applies it to Andrews A.F.B. downburst event simulation. This model stands on a new decomposition of downburst wind velocity which makes appear a synoptic background wind velocity component to combine with the classic downburst-related velocity component. In the aim of applying this new model to transmission lines structures in the future, the response of one known case of vertical structure (CAARC building) and one known case of cable structure (iced cable) is studied. The iced cable case is discussed further by simulating different downburst trajectories and a random sampling of the downburst wind field is processed in order to get statistics data from the structural response of the cable such as the correlation coefficients.