Modeling of Nonstationary Thunderstorm Winds and Their Impact on Structures and Infrastructures

Through exposure from the 1978 Northern Illinois Meteorological Research on Downbursts (NIMROD) and the 1982 Joint Airport Weather Studies (JAWS), thunderstorm downbursts have been recognized by the wind engineering community as phenomena deserving thorough investigation. They can be briefly described by a central, initial touchdown point, a high- velocity non-stationary wind field and a boundary layer that greatly differs from that of stationary winds. The life span of a downburst follows an evolutionary path starting from an intense vertical downdraft of wind that radially diverges while decaying over a short period of time (roughly 10 to 20 minutes). This outburst of wind is accompanied by a translational velocity, with which the downburst travels, thus producing a transient and non-synoptic wind field. Non-synoptic, nonstationary, short-duration thunderstorm downbursts and gust fronts are currently absent from the design standards except for very special structures (e.g., nuclear power plants). Difficult to capture from full-scale measurements and to replicate through wind tunnel experimentation, their nonstationary, evolving properties violate the principles of the “Davenport Chain” in wind engineering and thus limit the analysis for the structural responses that they induce. Since these windstorms have been identified worldwide as a source of peak design wind speeds, many research endeavors have been devoted to better understand their nonstationary loads and effects on structures and infrastructures. Nevertheless, studies of structures exposed to downburst and non-stationary gust front wind loads has lagged behind the many case studies conducted under atmospheric boundary layer (ABL), stationary wind load conditions. Advanced, post-graduate courses on wind engineering are currently being offered at many universities across Europe and the world. However, most existing courses do not address non-stationary wind field modeling and simulation. Consequently, there is a lack of understanding on non-stationary wind storm hazard risk and its consequences. This course fills this void and offers a review of the state-of-the-art, state-of-the-practice procedures and practices for the analysis of the thunderstorm phenomena as they relate to the structural design of buildings, bridges and wind turbine tower structures. Furthermore, the course addresses a multitude of topics, in a multi-disciplinary setting (atmospheric science, engineering, physics). The course will leverage various innovative developments of load and structural modeling, experimental methods and full-scale monitoring results to: - Provide science and engineering fundamentals that enable examination of various nonstationary flows; - Introduce dynamic similarity principles in nonstationary flow settings; - Equip participants with innovative methods to simulate the wind field of non-stationary thunderstorm downbursts; - Familiarize with the most advanced experimental methods and facilities; - Contextualize the load and analysis results with design standards, considering the effects of future warming wind climates.