Dynamic Response of Slender Vertical Structures Subjected to Thunderstorm Outflows

Abstract

This study examines the maximum alongwind dynamic response of slender vertical structures subjected to thunderstorms, comparing the induced maximum response with the one induced via synoptic events. Two real structures are considered as case studies: a lighting pole and a telecommunications tower. The comparison between thunderstorm- and synoptic-induced dynamic responses is performed through a critical analysis of three ratios characterizing the difference between the two phenomena: the reference wind speed, the mean wind profile, and the gust response factor. The comparison shows that the definition of the reference wind speed and the height of the nose tip of the thunderstorm mean wind profile are crucial for the maximum response, as well as for the dependence of the turbulence intensity on the roughness length. The results show that thunderstorms provide the design loading condition in most cases.

Vibration Energy Harvesting from Plates by Means of Piezoelectric Dynamic Vibration Absorbers

“…Turbulence of grazing flows used to collect energy from artificial piezoelectric grass [28] shows relevant PSD amplitudes below 50 Hz. Wind turbulence PSDs used for the design of civil structures show maximum amplitudes below 1 Hz [29][30][31]. The PSDs of traffic-induced vibrations show their main peaks below 20 Hz [32].…”

“…Owing to the dependence on the frequency squared (Equation ( 32)), the acceleration FRF shows the highest peak for the sixth mode. If the sizes of the plate have an order of magnitude of 1 m, they are much smaller than the typical length scale of wind turbulence that excites buildings [31]; therefore, pressure can be considered spatially uniform. For pressure fluctuations related to turbulence having smaller length scales, the possible excitation of higher-order modes has to be evaluated using more sophisticated methods like the acceptance integral [33]; nevertheless, also in this case, the first mode is the most excited [33].…”

Vibration Energy Harvesting from Plates by Means of Piezoelectric Dynamic Vibration Absorbers

“…Turbulence of grazing flows used to collect energy form artificial piezoelectric grass [20] shows relevant PSD amplitudes below 50 Hz. Wind turbulence PSDs used for the design of civil structures show the maximum amplitude below 1Hz [21][22][23]. The PSDs of traffic induced vibrations show their main peaks below 20 Hz [24].…”

“…Owing to the dependence on frequency squared (Equation (32)) the acceleration FRF shows the highest peak for the 6th mode. If the sizes of the plate have the order of magnitude of 1 m, they are much smaller than the typical length scale of wind turbulence that excites buildings [23], therefore pressure can be considered spatially uniform. For pressure fluctuations related to turbulence having smaller length scales the possible excitation of higher order modes has to be evaluated using more sophisticated methods like the acceptance integral [25], nevertheless, also in this case the first mode is the most excited [25].…”

“…where i is the imaginary unit. Introducing ( 24),( 25), (26), and( 27) in (23), this system of linear equations holds:…”