Wind Tunnel Testing and the Sector-by-Sector Approach to Wind Directionality Effects

We examine the sector-by-sector approach used by some wind tunnel operators to specify extreme wind effects. According to this approach the design of a structural member subjected to wind loads is adequate if the stresses induced by the largest sectorial wind speed with a 50year mean recurrence interval does not exceed the maximum allowable wind-induced stress for that member, sectorial wind speeds with a 50year mean recurrence interval being estimated separately for each of the eight 45° (or the 16 22.5°) azimuthal sectors. We show that this approach leads to estimates of wind effects that are unconservative (i.e., on the unsafe side), owing to their failure to consider the overall effects of winds blowing from all sectors.