Exposure factors and their specifications in current wind codes and standards

Wind exposure is one of the most complex issues in wind engineering and it results in the uncertainty of wind load evaluation. The specifications of exposure factor are provided in current wind load provisions to help designers determine the wind load on structures, in light of harmonizing and adopting on-going research investigations. However, there are discrepancies among various national wind provisions, as well as ambiguities in comparison with latest research results. This paper provides a comprehensive review on the studies related to exposure roughness and provides an overview of the relevant specifications in current wind provisions of [1] (USA), [2] (Canada), [3] (Australia), [4] (China), and [5] (Europe). Similarities and discrepancies of current wind load provisions are outlined in terms of exposure categories, minimum upstream fetch, and methodologies accounting for non-homogeneous exposures. Suggestions are offered to rectify some deficiencies of wind load provisions based on comparisons of wind pressures with field measurement data and wind tunnel experimental results. Moreover, recent advances in investigations regarding exposure factors have been illustrated. The research presented in the paper demonstrates a great potential to contribute to further development of wind standards and codes of practice, as far as the characterization of the upstream exposure is concerned, at the national and international level (ISO).