# Dynamic Response of Slender Vertical Structures Subjected to Thunderstorm Outflows
## 5 Conclusions and Prospects  
In this study, the thunderstorm gust response factor was generalized to the analysis of slender vertical structures, and it was employed for a comparison between the maximum dynamic response due to thunderstorms and synoptic events. Two real structures were considered as case studies; i.e., a lighting pole, regarded as a low-rise structure, and a telecommunications tower, regarded as a higher structure. The comparison between the maximum dynamic response due to thunderstorms and synoptic events was carried  
Figure 12: Maximum response ratios. Case (**a**) circles—dashed lines; case (**b**) triangles—solid lines; lighting pole (**a**); and telecommunications tower (**b**). out by investigating the role of the roughness length, the height of the nose profile, and turbulence intensity. From the comparison with TDA and TRS, it can be concluded that the TGRF was proven to be a robust and reliable tool for the estimate of the maximum response of slender vertical structures. In view of the results outlined, the TGRF was then adopted to carry out a comparison with stationary wind. The comparison showed that both 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. According to the available data collected in a thunderstorm-prone area for a return period of 50 years, it was pointed out how the velocity ratio is significantly large, and that the thunderstorm provides the design loading condition in most of the cases except for the taller structure, where the synoptic wind provides the design conditions only if the nose tip is at the lowest height. In this framework, it was shown that accounting for the transient dynamics in the estimate of the gust response factor is beneficial for the reduction in the maximum response due to thunderstorms. Moreover, the dependence on the roughness length is crucial for a proper estimate of the maximum response and wind loading. The results shed light on some important aspects that need to be addressed. Firstly, the importance of carrying out an accurate estimate of the reference wind speed through separated statistical analyses of thunderstorms and synoptic events was highlighted, especially in thunderstorm-prone areas. Secondly, further studies are necessary for the definition of suitable analytical models that are able to account for the dependence of the vertical mean wind speed profile and turbulence intensity on the roughness length. In view of these results, the evaluation of the wind loading due to thunderstorm outflows is essential for a safer and cost-efficient design of structures, and the introduction of proper guidelines in codes and standards is advisable. In this framework, the TGRF approach represents a robust and handy tool for engineers to properly estimate the maximum response and wind loading caused via thunderstorms. Future studies will be aimed at carrying out a comparison between the maximum dynamic response registered from a monitored slender structure and the one estimated through the TGRF technique. Conceptualization, L.R. and F.T. ; methodology, L.R. and F.T. ; software (Matlab 2020), L.R. and M.G; validation, L.R. and M.G. ; formal analysis, L.R. and M.G. ; investigation, L.R. ; resources, L.R. and F.T. ; data curation, L.R. and M.G. ; writing--original draft preparation, L.R. ; writing--review and editing, F.T; visualization, L.R. and M.G. ; supervision, F.T. All authors have read and agreed to the published version of the manuscript. This research was funded by the European Research Council (ERC) under the European Union's Horizon 2020 Research and Innovation Program (grant agreement No. : 741273) for the project THUNDERR--Detection, simulation, modelling, and loading of thunderstorm outflows to design wind-safe and cost-efficient structures--supported by an Advanced Grant 2016. The data used for this research were recorded via the monitoring network set up as part of the European Projects Winds and Ports (grant No.