Gust Buffeting of Slender Structures and Structural Elements: Simplified Formulas for Design Calculations and Code Provisions

The lack of simple methods to determine the simultaneous alongwind, crosswind, and torsional loading and response of slender structures and structural elements is a major shortcoming in design practice and wind standards. In this regard structural engineers are now familiar with determining the gust factor and dynamic coefficient of the alongwind loading and response. Meanwhile, they are becoming more and more familiar with evaluating the crosswind loading and response of slender structures subjected to critical vortex shedding conditions. On the other hand, structural engineers often forget to inspect or ignore the crosswind and torsional loading and response attributable to gust buffeting, at most limiting themselves to carrying out static analyses based on peak wind actions and unit dynamic coefficients. This is typical, for instance, in the design of bridges and footbridges, chimneys, lighting poles, telecommunication towers, and single elements of lattice structures and industrial frameworks. However, crosswind and torsional actions on slender structures and structural elements caused by the buffeting loading frequently exceed the alongwind buffeting loading and the crosswind loading caused by critical vortex shedding. In addition, provided that crosswind and torsional actions attributable to the buffeting loading do not prevail on the alongwind ones, their evaluation cannot be ignored and their load effects have to be combined with the alongwind ones. Starting from a general but quite hermetic solution developed by Piccardo and Solari at the end of the 1990s, this paper introduces a series of simplifications that, without limiting the correctness and generality of this approach, lead to simplified formulas for evaluating the alongwind, crosswind, and torsional equivalent static actions on slender structures and structural elements, which can be easily transferred to design practice and code provisions. These formulas also correct a slight mistake in the previous solution.