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RE: 2006 IBC Wind Load question

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Dennis, I'm not sure where you heard that "design wind loads can be designed more like the 97 UBC if the design values are supplied by the building official".  I agree with Scott that the method used for design is independent of whether the wind speed came from the maps or the building official when using IBC/ ASCE 7.  The "Simplified Method" can be used with either source for wind speeds as long as you meet the limitations of the method. 
I tend to use the Analytical Procedure in ASCE 7, simply because I've had enough structures that do not meet the limitations of the Simplified Method such that I prefer to stick to one method for all of my designs.
Bill Sherman

From: Scott Maxwell [mailto:smaxwell(--nospam--at)]
Sent: Saturday, August 25, 2007 9:21 PM
To: seaint(--nospam--at)
Subject: RE: 2006 IBC Wind Load question

In my experience, unless the local jurisdiction completely modified the wind provisions for use in their local building code, the only item that you might get from the local code official is the wind speed.  But, that would only really likely happen in areas along the East and South Coasts (i.e. hurricane zones where the wind speed maps get a little tough to is good to check with the local official as to what wind speed to use...OR in special wind regions typically in mountous regions).  The vast majority of the US is 90 mph (with the exception of the three West Coast states that magically have 85 mph winds when you cross the border into those states).
The only other thing that the code official MIGHT dictate is the Exposure Category, but that has been EXTREMELY rare in my experience.
Beyond that, there should be no difference between getting values off the map or getting them from the code official.  The process is still the same...unless they have replaced the typical IBC/ASCE 7 wind provisions with something else or modified those provisions extensively.
Point is that I don't see a difference between getting wind parameters from a code official vs. a map in terms of the process for determining the wind loads.  It is the same is just that first little piece of data used to input into the process might differ.
Adrian, MI
-----Original Message-----
From: Dennis Wish [mailto:dennis.wish(--nospam--at)]
Sent: Saturday, August 25, 2007 8:49 PM
To: seaint(--nospam--at)
Subject: 2006 IBC Wind Load question

I’ve discussed the design of wind loads for the next generation of IBC codes that California will adopt in 2008 to replace the 97 UBC. As most of you who use the UBC or California building code are aware, the 97 UBC is a fairly straight forward method to determine wind design.

Most of the engineers I’ve spoken to who are in IBC country have mentioned that they rarely use more than the windward side of loading and have not used the more extensive load design methods that check windward, leeward, uplift on eaves and on interior roof areas (where there is a percentage of space exposed to consistent wind loads). I do check uplift on the eaves but only if the uplift occurs on a very light roof such as asphalt shingle or metal. When clay tile is use and the exterior dead load exceeds a lightweight tile then I find that the roof weight rarely shows that uplift occurs. Of course I do not live in a high wind area that exceeds 90-psf wind gust.

My concern is that I have to add the wind design into the next version of MultiLat and as many of you know I have been suffering with the learning process based on the latest ASCE wind load design methods.

My question is whether or not you think that the values we need to design to will be provided by the local municipality in which you will design your structure or if you will be required to work everything out by maps and government references. Currently the building department sets the limits we design to and I’ve never had to rely on reference maps from government references.


Have any of you worked up a worksheet design method of the simplified wind load conditions to be used with the 2006 IBC and are willing to share it with me to help me understand the steps. I’ve been told that the design wind loads can be designed more like the 97 UBC if the design values are supplied by the building official. I wish to add this to MultiLat, but would prefer to use a method based on inputting local conditions provided by the building department your structure is designed for.

I would like some advices as to how many of you plan to design wind loads in the 2006 IBC and what you have done in the past AND what you expect to do in the next code cycle. If you are willing to share your ideas with me, I would be greatly appreciative. However, remember that I am in the mindset that whatever I create is submitted for public domain so that others can save a bit of time.




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