Mean Recurrence Intervals of Ultimate Wind Loads.
Mean Recurrence Intervals of Ultimate Wind Loads.
(644 K)
Simiu, E.; Heckert, N. A.; Whalen, T. M.
OMAE98-1218;
Offshore Mechanics and Arctic Enginering (OMAE), 17th
International Conference. Proceedings. American
Society of Mechanical Engineers. OMAE98-1218. July
1998, 1-6 pp, 1998.
Keywords:
wind velocity; extreme values; wind engineering;
statistics; structural engineering; ultimate loads
Abstract:
The attention of wind engineers and extreme value
climatologists has been focused in the last few decades
on estimates of basic wind speeds, that is, wind speeds
with 50- or 100-yr mean recurrence intervals (MRIs).
Recently, however, efforts have been reported on MRI
estimation for speeds including the design strength or
causing member failure. These efforts have benefited
from progress in extreme value theory, notably the
development of 'peaks over threshold' methods used in
conjunction with the Generalized Pareto Distribution.
According to results based on such methods extreme wind
speeds are best fitted by extreme value distributions of
the reverse Weibull type which, unlike other
distributions used in the past, have finite upper tails.
We note results according to which the ASCE 7-93
Standard and its 1980s predecessors specify wind load
factors that place structures in hurricane-prone regions
at substantially higher risk than structures in
non-hurricane regions, and comment on changes required
in Standard provisions in this respect. We also review
results on the effects of wind directionality. On
average, estimates of wind loads with relatively short
MRIs, obtained by disregarding wind directionality
effects, are conservative in relation to estimates that
take directionality into account. However, the
conservatism decreases asthe MRIs increase and may
become marginal for speeds associated with wind-induced
failures. We report and comment on the result that
estimated tails of distributions that best fit samples
of hurricane wind speeds are somewhat shorter than
estimated tails for samples of squares of hurricane wind
speeds. An Appendix provides instructions for accessing
electronic files containing wind speed data and computer
program listings.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899