A 90mph gust windefinition is last how many seconds?
A 90mph gust windefinition is last how many seconds?
(OP)
I got a customer enquiring about a 90mph (or 100mph) gust definition. His question is how long this 90mph gust last will be defined as 90mph wind. 3s? or 5s?, can anybody help me to answer this question? Thanks






RE: A 90mph gust windefinition is last how many seconds?
RE: A 90mph gust windefinition is last how many seconds?
RE: A 90mph gust windefinition is last how many seconds?
RE: A 90mph gust windefinition is last how many seconds?
RE: A 90mph gust windefinition is last how many seconds?
If the wind was sustained at 90 mph, then I suppose due to natural variations in the turbulent flow, you would actually have 3-second gusts that were higher than 90 mph, so it wouldn't be a 3-sec-90 mph wind anymore. And if you had a 90 mph-3 sec wind condition, you might find higher speed gusts that had shorter durations than 3 seconds.
RE: A 90mph gust windefinition is last how many seconds?
RE: A 90mph gust windefinition is last how many seconds?
If the 3s gust is 90mph then the 1s gust would be larger possibly 100mph and the 5s gust would be lower say 80mph. As the code is based on the 3s gust this is the speed you should use in your calculations.
A lot of statistical analysis of wind tests goes into the factors that you find in the codes.
RE: A 90mph gust windefinition is last how many seconds?
Let me then say, there is only steady wind in the lab and it is not found in the real world. The ASCE wind maps present a standard that we can design for. They measured winds at points continuously during storms then chopped the data into 3 second time periods and took the average over those 3 second periods and published the highest average as a map of contour lines. The map is for a 50 year MRI storm. You can choose factors to convert the return period to different times.
These aforementioned measurements were for continental winds away from hurricane zones. I believe the hurricane zones used Monte Carlo simulations to obtain the 50 year MRI wind speeds because we only get 1 hurricane at a point on the coast every few years. This is why Exposure D is not appropriate for coastal areas in hurricane zones which should use C.
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RE: A 90mph gust windefinition is last how many seconds?