The safety and sustainability of the built with regard to the natural and anthropogenic actions are a primary goal of engineering. The wind is the most destructive natural phenomenon: 70% of the damage and death caused by nature every year in the world comes from the wind. Evaluating its actions is therefore crucial for society and its economy. The European wind climate and that of many countries are dominated by extra-tropical cyclones and thunderstorms. The genesis and evolution of cyclones is known since the 1920s. Its actions on construction have been framed since the 1960s and engineering still uses these models. Thunderstorm is a complex, mysterious and devastating phenomenon that results in actions often more intense than cyclonic ones. Despite this awareness and the research in the last thirty years there is no model of the thunderstorm winds and their actions similar to that established over half a century ago for cyclones. Likewise, there is no unified framework for cyclone and thunderstorm wind actions. This occurs because the complexity of thunderstorms makes it difficult to establish realistic and simple models; their short duration and small extension limits the available measures; there is a clear gap between research in atmospheric sciences and wind engineering.

Despite a lot of research, literature lacks of a thunderstorm model shared by scientific community, consistent with physical properties and suitable for simple engineering evaluations. This objective aims at formulating a novel, interdisciplinary and unitary model of thunderstorm outflows, with the dual prospect of being itself a challenging scientific result and, at the same time, of being a robust basis to carry out engineering analyses with a ground-breaking impact on construction and society. This model would be the counterpart of the model diffused and shared worldwide from the ‘60s to represent synoptic events.

Outflow signals will be decomposed into component functions and statistical averages will be evaluated. LiDAR and antenna mast data will be investigated to determine the time-space evolutionary wind speed profiles. An unprecedented set of large-scale downbursts will be simulated and detected. Wind tunnel tests will be also performed in smaller scale facilities to evaluate scale effects using field measurements as reference data. Comparative simulations of downbursts will be performed by impinging wall jet and sub-cloud models through RANS and LES. Research will be carried out to apply sub-cloud models by LES. Field measures will be used as reference data to calibrate wind tunnel and CFD simulations. A wide collection of information will be gathered (e.g. GFS, MSG, Radar Doppler images, lightning data) to classify the weather scenarios in which thunderstorms occur. Research will be carried to link weather scenarios and wind speed data. Advances in downburst forecast will be pursued. Damage and losses due to windstorms will be traced to separate and classify the impact of cyclones and thunderstorms, gathering a catalogue of links between wind causes and effects.

Two towers will be equipped by anemometers, accelerometers and strain-gauges, and subjected to wind tunnel tests. This monitoring will provide simultaneous measurements of the outflow velocity and structural response. Closed form solutions will be disclosed to thunderstorms by generalising the equivalent wind spectrum to transient winds. Three complementary methods will be set to evaluate equivalent static loading: time-domain analysis, response spectrum technique and evolutionary spectral method. The classical unique wind loading will be separated into two loading conditions for cyclones and thunderstorms, producing a novel set of partial and combination factors for thunderstorms. Research will be carried out to merge this new philosophy into performance-based design.