Abstract Summary
Structural monitoring is getting growing attention for system identification, damage identification, and capacity assessments of structures. On the other hand, wind measurement using a network of anemometers has always been a typical feature of meteorological stations. With the growing interest to study transient wind events that last short periods, closely spaced anemometers with a high frequency of measurement are also becoming common. However, the simultaneous measurement of wind and structural response through full-scale monitoring is still very rare in the literature. If available, the data from simultaneous wind and structural monitoring could be crucial to study the impact of wind phenomena that do not have a well-defined theoretical framework for wind load calculation. One of such phenomena is the downburst outflow wind due to thunderstorm, a strong convective meteorological event whose frequency and intensity is increasing because of climate change. Due to their limited dimension in space and time, downburst outflows due to thunderstorm events have been rarely measured in full-scale. In the past 20 years, there were many efforts to study the response of structures under downburst winds through wind tunnel testing, computational fluid dynamics, and theoretical methods. However, the efforts were not supported with full-scale wind and structural response monitoring of structures under real downburst outflow wind. The wind engineering research group in University of Genova (Italy) developed a comprehensive research project addressed to the study of thunderstorm effects on structures, realizing three full-scale monitoring systems measuring simultaneously wind velocity and structural response. This research presents long-term full-scale monitoring of a lighting pole to study its dynamic response under downburst wind. Initially, the dynamic properties of the structure such as modal frequencies, modal shapes, and damping ratios are investigated through operational modal analysis. Then, a method that separates downburst winds from synoptic winds and gust fronts was applied to identify the occurrence of downburst winds during the monitoring period. Through this method, possible downburst events were identified. The response of the pole measured through accelerometers and strain gauges was analyzed to obtain the displacement time history of the pole during the identified downburst events. The simultaneous wind and structural response data were analyzed to study the correlation between wind speed and structural displacement parameters. The time histories of mean wind speed squared and mean structural displacement was found to be highly correlated. Whereas the time histories of turbulence intensity and the root mean square of displacement fluctuation were found to be negatively correlated. Because of the structural simplicity, availability of the dynamic properties, and the provision of wind and structural response registration, this research will serve as a basis for the validation of analytical downburst wind load calculation techniques.
