Wind Design Pressures
Wind Design Pressures
(OP)
Design pressures at wall corners and roof edges calculated per ASCE 7 are to be applied over a distance a. This is listed as 0.1 x width, 0.4h, minimum of 3 feet. In the 1997 UBC this used to be limited to a maximum of 10 feet. Is ther a similar maximum now in ASCE 7?






RE: Wind Design Pressures
RE: Wind Design Pressures
RE: Wind Design Pressures
RE: Wind Design Pressures
It would be a whole lot easier if you didnt have to flick back and forth to get values from tables.
RE: Wind Design Pressures
I asked at a seminar about six years ago why the code changed wind design so much since it didn't appear to be a problem. The answer was this was more accurate (?) and since everyone had computers, there would soon be a computer program that would take care of it for us.
For a small fee, of course.
RE: Wind Design Pressures
RE: Wind Design Pressures
So where's the benefit? I have trouble with any claim that the increased complexity of ASCE 7 is justified by increased accuracy. Definitley a case of false precision.
RE: Wind Design Pressures
Dik
RE: Wind Design Pressures
The wind loads derived from these codes are not a real representation of what happens in nature, but rather produce expressions that work. I think ASCE 7 has lost site of this.
RE: Wind Design Pressures
Ghosh's articles, (2 articles) written in the Structual Engineer magazines are well written and it is the first grenade launched during this war to simplify the wind provisions.
Excuse my rant, but as structural engineers, who have to deal with this everyday, should scream from the highest mountain that these current provisions are B.S. and we should not have to rely on the computer just to get the forces. It is insane.
RE: Wind Design Pressures
Yes, ASCE 7 is a bit more complicated and poorly presented than other code documents. My suggestion is that you boil it down with a throrough going over then produce a spreadsheet with your most common conditions. At least that works for my purposes.
RE: Wind Design Pressures
RE: Wind Design Pressures
RE: Wind Design Pressures
RE: Wind Design Pressures
RE: Wind Design Pressures
In my opinion it would be almost impossible to estimate with calculations exactly what the wind pressures will be in the "real world". What it needed is a simplified method that is truly simple that can be applicable for many "average" structures.
In my state before we adopted the IBC all you had to do was look in a table that listed wind pressure as a function of building height-no calcs involved. I'm not aware of a lot of wind induced failures in my area that have been attributed to a deficiency in design wind pressure. In fact, with V=90 and exposure B my MWFRS pressures are relatively close to the old table values.
I'm not advocating a return to that old system, but simplifications can certainly be made to the IBC/ASCE7 provisions. Calculating wind pressures should not be an academic research project.
RE: Wind Design Pressures
RE: Wind Design Pressures
just an fyi for engineers designing in the state
RE: Wind Design Pressures
We now are all familiar with the code and it is used without too much difficulty as we know the shortcuts...
There is some pretty good software available for free from cold formed steelwork suppliers. I know the US is different but this may well also happen there.
Structuralaggie makes a very good point: "How many perfectly rectangular buildings are they building these days anyway?"
Maybe we should all be lobbying the relevant people to introduce more building types which better reflect those which we actually do design?