Analytical methods for estimating the gust-excited response of cantilever vertical structures

Gust buffeting of structures is a main topic of research developed in wind engineering over the last 40 years. This paper provides a general framework and a critical survey of this matter, focusing attention on the methods developed at the University of Genoa with reference to cantilever vertical structures, e.g. buildings, towers and chimneys. Alongwind, crosswind and torsional gust-excited effects are first determined as the superimposition of static, quasi-static and resonant parts. The static and quasi-static parts are evaluated by the influence function technique; the resonant parts are associated with the fundamental modes of vibration. The equivalent static forces are defined through three alternative rules referred to as the gust factor, loading combination and global loading techniques. The solutions may be obtained by estimating the wind loading experimentally and calculating the response numerically. A different and more appealing approach consists in setting a hierarchy of hypotheses coherent with classical models and solving the problem in closed form. This makes engineering applications straightforward and enables to assess general structural tendencies. The comparisons between the results provided by analytical methods, numerical algorithms and experimental tests show the robustness of the models proposed. The conclusions deal with integrated procedures and proper orthogonal decomposition. Integrated procedures use analytical methods, numerical algorithms and experimental tests jointly; embedded in such a context, analytical methods allow the solution of wind engineering problems otherwise almost prohibitive. Proper orthogonal decomposition offers innovative tools for expressing the gust-excited response as a double series of structural and loading modes; the search for the eigensolutions of loading in closed form opens the door to a new generation of analytical methods.