Wind direction and hurricane-induced ultimate wind loads

A consensus on the wind directionality issue is needed for the validation by building officials of the wind-tunnel procedure allowed by the ASCE 7-95 Standard, and for the development of provisions for wind loads that use large aerodynamic and climatological databases. As a contribution to the debate needed to achieve such a consensus, we describe an updated method for estimating wind loads that takes into account the directional dependence of the aerodynamic coefficients and the extreme wind climate, and uses the 'peaks over threshold' approach for the estimation of extremes. For hurricane-prone regions, assuming epistemic uncertainties are negligible, we estimate mean recurrence intervals (MRIs) of wind loads inducing the design strength, obtained from 50 yr loads via multiplication by a factor specified by the ASCE 7-95 Standard. For typical aerodynamic coefficients with strong directional preference, depending upon location and building orientation those estimated MRIs varied between less than 1000 to more than 10 000 yr. If epistemic uncertainties were taken into account the estimated MRIs would be shorter. We also found that for loads with very large MRIs the common practice of disregarding direction effects is not necessarily conservative from a structural engineering viewpoint. (C) 1998 Elsevier Science Ltd. All rights reserved.