Structural response to non-stationary thunderstorm out-flows: multi-variate vs equivalent mono-variate simulation

The European Projects “Wind and Ports” and “Wind, Ports and Sea” gave rise to an extensive wind monitoring network in the High Tyrrhenian Sea area, from which many records of thunderstorm outflows were extracted. Initially, they were analysed to inspect their statistical properties. Later on, a hybrid multi-variate strategy for simulating the non-stationary wind field of the thunderstorm outflows was formulated and implemented to determine the time-domain response of structures. This paper shows the conceptual and numeric simplifications involved by embedding the equivalent wind spectrum technique, a method developed in a stationary framework, within the above non-stationary formulation. It leads to generate a multi-variate non-stationary wind field through the simulation of a mono-variate stationary process, without any relevant loss of precision.