Thunderstorm gust response factor: General tendencies and sensitivity analysis

This paper aims to provide a sensitivity analysis of the thunderstorm gust response factor. The study is based on the extension of the gust response factor technique to the assessment of the maximum dynamic response of structures to thunderstorm outflows, starting from an evolutionary spectral model of the thunderstorm wind speed. The thunderstorm evolutionary spectral model depends on the modulating function of the slowly-varying mean speed, which is a function of two parameters, i.e. the background mean wind speed and the duration of the intense phase of the outflow. Starting from 129 full-scale thunderstorm records, the parameters of three different analytical models of the modulating function are extracted and a statistical analysis is carried out defining their range of variation. The dependence of the gust response factor on the analytical expression of the modulating function is studied as well as its sensitivity to the parameters of the function. Results show that the dependence of the gust response factor on the analytical expression of the modulating function is negligible, while it is very sensitive to the variation of the background wind and duration of the intense phase, especially for flexible and lowly-damped systems.