Wind Speed Maps for the Caribbean for Application with the Wind Load Provisions of ASCE 7
structure located in the hurricane prone region is about twice that of the 50 year return period load. In the non-hurricane prone region this difference is only a factor of 1.6 (i.e. the wind load factor). To ensure the annual probability of exceeding the ultimate wind load for the hurricane and non-hurricane prone regions are the same, a load factor of 2 would have to be applied to the 50 year return period design wind speed for a building designed at the hurricane prone location, whereas a load factor of 1.6 is applied to the non-hurricane wind load.
Alternately, from Equations B-1 and B-3, a hurricane importance can be defined as
IH = 2 /1.6 = 1.12
Or more generally,
I H = (V709 /V50 ) / WLF
Wind Load Factor
100 Return Period (Years)
F i g u r e B - 1 W i n d l o a d f a c t o r ( V T / V 5 0 ) 2 f o r H u r r i c a n e a n d N o n - H u r r i c a n e W i n d S p e e d plotted vs. return period. s
Thus when the 50 year return period wind speed in the hurricane prone region is multiplied by the hurricane importance factor, the annual probability that the ultimate load is exceeded in either location is about the same.
Instead of producing maps of hurricane importance factors to be applied to the nominal 50-year return period wind speed, a design wind speed can be defined as:
Vdesign = V709 / WLF ≈ V700 / WLF