Despite the evidence of energy transmission tower collapses due to tornadic events in the Brazilian territory, no national study treats the issue under strictly structural focus. In this context, as a starting point, mechanical global actions due to an approximate mathematical model of a F3 tornado, compatible with the Brazilian threat on two towers, one guyed and one self-supported tower, are evaluated; these tower models are largely used in the Paraná-Uruguai River Basins, critical on such occurrences. Comparisons with actions foreseen in design are performed in order to obtain the critical loading situations. Usage of tornadic response spectrum practices is proposed and particular aspects of tornadic loads on tower structures are analyzed.

Brazilian territory is situated on an intraplate region with low seismic activity, and so, it is important to answer an old question that remains unanswered: "Should standard building structures in Brazil be guaranteed by a seismic resistant design?" In this way , a methodology is described and used to evaluate the annual failure probability of a structure model subjected to ground motions compatible with a defined provincial seismicity; the model strength is taken as the maximum shear and overturning moment at the base. One considers five different structure models for each Brazilian state capital city and evaluates the annual failure probability which provides arguments to answer the above question.