Performance-based design of steel towers subject to wind action

Performance-based Wind Engineering (PBWE) is a novel design philosophy that aims to identify and quantify the uncertainties involved in structural design, in order to ensure predictable performance levels to engineering structures. Due to the recent proposal of the methodology and formulation complexity, there are few studies related to PBWE, each presenting different limitations. This paper proposes an application of the Performance-based Wind Engineering methodology to the probabilistic analysis of steel towers, evaluating different calculation models for the estimation of wind forces on this type of structure. Uncertainties involved in the characterization of the wind field and the structural strength were investigated, and two procedures of the Brazilian winds standard NBR6123:88 for the estimation of wind forces on steel towers were analyzed. A case study concerning the reliability estimation of a telecommunication tower was also conducted. It was found that both studied calculation models lead to similar safety levels, and that the design of towers considering that wind always blows from the worst direction is too conservative. It is also shown that, in PBWE, minimum cost design can be guided by assigning same target reliability, but different mean recurrence intervals for different performance levels.