Sensitivity analysis of structural response to thunderstorm downburst models

Most studies on structural response under downburst wind loads rely on a single downburst model or limited wind measurements. Uncertainties in key modeling parameters further complicate accurate response predictions. Furthermore, there are no standard formulations for power spectral density (PSD) or coherence functions specific to downburst turbulence characteristics. As a first step toward developing a probabilistic uncertainty quantification framework, this study examines the impact of various modeling assumptions and parameter uncertainties on structural response, utilizing the CAARC building as a testbed. A hazard analysis was conducted to predict the design-level downburst wind speed based on NOAA database records over 45 years. A global sensitivity analysis was utilized to rank the influence of uncertain modeling parameters. The results indicate that the structural response is mainly sensitive to maximum wind speed in the vertical profile. Other moderately influential parameters include the stagnation region radius, the building's position relative to the downburst center, and the mean turbulence intensity. While different vertical wind profile models affect the mean responses, they have minimal impact on the response probability distribution. In contrast, the coherence function significantly affects the probability distribution of maximum building drift, whereas variations in PSD functions have negligible effects.