The behavior of welded metallic structures against the wind actions [Il comportamento delle strutture metalliche saldate nei confronti dell'azione del vento]

There are many metallic structures, taken as a whole or at level of individual elements - including lighting poles, telecommunication towers, pylons, wind turbines, containers unloder, structures supported by cables - with relevant slenderness, flexibility, lightness and low dissipative capacity. These structures, inevitably exposed to wind dynamic actions, have been occuring an endless series of collapses and failures of welded joints. The analysis of the collapses show a phenomenon almost completely ignored in the past: fatigue caused by wind actions. In many cases, the collapse takes place from a few days to a few months of structure completion. It is partly due to lack of expertise in weld execution, but it is mainly a consequence of lack of knowledge of wind-fatigue. The article presents an overview of the physical phenomena and structural properties that determine this kind of failure. The prospects, now ripe, to spread calculation procedures for estimating such failure and avoid it are also discussed