Author Topic: Wind Speed Maps - ASCE 7-16  (Read 236 times)

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Offline Medeek

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Wind Speed Maps - ASCE 7-16
« on: March 09, 2018, 11:12:56 am »
I don't know about the rest of you but when I look at the new wind speed maps in the ASCE 7-16, in particular the eastern United States I find the contour lines a bit confusing.  With that in mind I spent a couple minutes this morning trying to fill in some of blanks so to speak, see below:



Its obvious that there a number of saddle points in the isolines and that is what complicates things at first glance.  I am curious how well these hand sketched isolines would correlate with the ASCE hazard tool.

The way the map is shown in the printed manual doesn't define the isolines in enough detail in my opinion, too much is left to interpretation and user error.  The one spot value at the end of Lake Michigan is a case in point. 
Nathaniel P. Wilkerson, P.E.

Offline Medeek

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Re: Wind Speed Maps - ASCE 7-16
« Reply #1 on: March 09, 2018, 11:14:26 am »
I suppose one could argue that the discrepancy caused by poor interpolation will probably result in a wind speed difference of only 2-3 mph which will not drastically alter the wind speed analysis and loads calculated for a structure.  However, I would argue that we are doing engineering here not just throwing around warm fuzzy numbers that are somewhere in the ballpark of where they need to be.  If this is the case then we can probably dispense with most of our current, overly complicated wind load chapter and all its factors and other accoutrements.  Why go to all the trouble to devise such a complicated wind load analysis when don't really even know the wind speed for a particular site? 

This brings to mind the numerous discussions regarding significant figures that I had from my university professors back in the day.  We are misrepresenting our data and falsifying its accuracy when we use such ambiguous maps but then turn around and try to provide such in depth analysis with our complicated algorithms.
Nathaniel P. Wilkerson, P.E.