IBC 2012 and ASCE 7-10 Wind Design
IBC 2012 and ASCE 7-10 Wind Design
(OP)
The jurisdiction that I do most of my work in is preparing to make the switch to IBC 2012 as the governing code. I am in a coastal hurricane prone region with a Vasd = 120 mph. Using the IBC 2012 charts for Risk Category II the Vult = 130 mph. I understand the differences in the codes and modified load combinations but using the new code both my MWFR and C&C design pressures are about 30% less with IBC 2012 than with IBC 2009. Has anyone else run into lower design wind pressures? I thought that even though the nomenclature within the code has changes, design values would be similar.






RE: IBC 2012 and ASCE 7-10 Wind Design
RE: IBC 2012 and ASCE 7-10 Wind Design
RE: IBC 2012 and ASCE 7-10 Wind Design
RE: IBC 2012 and ASCE 7-10 Wind Design
Perhaps double check here: http://www.atcouncil.org/windspeed/
RE: IBC 2012 and ASCE 7-10 Wind Design
I just checked for the areas west and north of here and they have the same design wind pressure regardless of IBC. Vasd = 90 mph has almost the same design pressure as Vult = 115 mph.
Is it possible that the IBC 2009 was 30% conservative for this area? This seems awfully high.
RE: IBC 2012 and ASCE 7-10 Wind Design
RE: IBC 2012 and ASCE 7-10 Wind Design
EIT
www.HowToEngineer.com
RE: IBC 2012 and ASCE 7-10 Wind Design
http://www.atcouncil.org/windspeed/
RE: IBC 2012 and ASCE 7-10 Wind Design
http://www.atcouncil.org/windspeed/index.php?optio...
After reading these responses and the ASCE commentary, I guess that what I am getting is accurate. It just seems to a huge drop to me. We have had a lot of close calls with hurricanes but no direct hits in my lifetime.
Thank you to everyone for your help
RE: IBC 2012 and ASCE 7-10 Wind Design
I had a project recently in Northeast Florida (St. John's County or maybe Clay County) and found a similar drop in wind pressures once making everything apples to apples. They have advertised this as either resulting in the same pressures or 10-15 % less pressures. In fact the wind contour changes were exactly the same as yours. A category II building going from ASCE 7-05 wind speed equal to 120 mph up to only an ASCE 7-10 wind speed of 130 mph. A seminar I went to said the contours are based on a lot more hurricane data than the old maps and that is the reason. At any rate my reaction was just like yours. I was very nervous at first.
So on an apples to apples basis if you are getting lower wind pressures it has more to do with the recalibration of the maps. And even though I've been working with the new ASCE 7-10 for about a year now I still find the new load factors to be annoying. I don't mind all the new wind maps for each building type such a big deal. But the load factors are a pain.
John Southard, M.S., P.E.
http://www.pdhlibrary.com/