Thunderstorm-induced actions on tall buildings

Thunderstorm-downbursts are characterized by intense downdrafts that impact the Earth’s surface, generating strong radial outflows and ring vortices. Unlike synoptic wind events, downbursts exhibit distinct features, including a nose-shaped mean wind speed profile and non-stationary characteristics within 10- to 60-minute time intervals. Despite these differences, structural wind loading is still evaluated using Davenport’s model, originally developed for extra-tropical cyclones, without considering the unique properties of thunderstorm outflows. In regions with a mixed wind climate, thunderstorms can significantly influence design wind speeds, making their study essential for modern wind engineering. Wind loads are typically evaluated using wind design codes or wind tunnel testing. Wind tunnel experiments provide a practical and cost-effective method for assessing wind effects on civil engineering structures, particularly tall buildings. However, conventional wind tunnels are designed for boundary layer wind simulations and require specialized devices to accurately replicate thunderstorm characteristics. Within this context, this research investigates thunderstorm-induced wind loads on tall buildings, aiming to bridge the gap between real-world thunderstorm dynamics and structural wind design. The study begins with a comprehensive analysis of full-scale measurements to better understand the characteristics of thunderstorm downbursts relevant to wind loading assessment. Wind data from anemometers and LiDAR systems are utilized, with LiDAR offering valuable multi-level wind information that remains scarce in existing literature. A statistical analysis is then conducted to estimate basic wind speeds for individual events and mixed distributions at the studied location. Building on these insights, wind tunnel experiments are performed. First, a passive device—a specially designed grid—is developed to replicate the nose-shaped mean wind speed profile and assess its effects on tall buildings. The device is validated for its adaptability, accounting for variations in key thunderstorm properties such as nose height and turbulence intensity. Subsequently, experimental tests are conducted on a benchmark building using high-frequency force balance and high-frequency pressure integration techniques. The results are compared to conventional synoptic wind events, evaluating wind loads and structural responses based on three key parameters: reference wind velocity, mean wind vertical profile, and turbulence intensity. This comparative analysis provides deeper insights into the role of these factors and advances research on thunderstorm-resistant building design. Finally, a real case study is conducted under worst-case thunderstorm conditions, analyzing wind-induced loads and responses and compared with synoptic winds at a specific construction site. The study also incorporates design wind speeds derived from the independent distribution of the predominant wind types at the location.