A combined risk framework for quantifying design wind load incorporating future unsheltered conditions

When using the wind tunnel procedure, the ASCE 7 and NBCC 2020 suggest additional testing to determine the impact on wind loads when specific influential buildings are removed. The unsheltered test configuration informs the lower limit of the design wind loads. For example, loads based on the wind tunnel test are not to be less than 80% of the analytical prediction based on ASCE 7, but an unsheltered configuration can justify reducing the lower limit to 50%. Determining the influential sheltering building requires engineering experience and judgement and is inevitably subjective. The absence of an influential building usually results in the proposed building being more exposed to higher wind loads. The removal of the influential building creates an arbitrary case that assumes it would be demolished and not replaced during the design working life of the proposed building. Removing multiple influential buildings simultaneously is more onerous and even less likely. Therefore, this study uses building service life datasets for many high-rise buildings to develop a probabilistic model of the removal scenario. This model combines wind tunnel test data to examine the effect of the service life of the influential buildings on the determined design wind loads in the unsheltered configuration. The results provide insights into designing and determining the unsheltered wind tunnel test configuration and recommend lower limits based on the unsheltered wind tunnel test configurations.