ASCE 7 - Flat roof wind uplift
ASCE 7 - Flat roof wind uplift
(OP)
Just taking a poll here of what others typically do.
This is speciically geared toward wind analysis of simple one-story buildings with flat roofs.
By the specific provisions of ASCE 7, the main wind force resisting system (MWFRS) wind loads for buildings provide for the following pressures (Method 2):
1. Windward wall
2. Leeward wall
3. Parapets
4. Rooftop equipment
5. Uplift on the flat roof
It seems that a lot of engineers sort of ignore item 5 in design. If so is this correct?
The issue is that if you have an interior frame with an X-brace (two columns, a roof beam and an X) wouldn't the roof uplift be somewhat important to include in the calculattions involving the brace...specifically for the footings under the two columns?
This is speciically geared toward wind analysis of simple one-story buildings with flat roofs.
By the specific provisions of ASCE 7, the main wind force resisting system (MWFRS) wind loads for buildings provide for the following pressures (Method 2):
1. Windward wall
2. Leeward wall
3. Parapets
4. Rooftop equipment
5. Uplift on the flat roof
It seems that a lot of engineers sort of ignore item 5 in design. If so is this correct?
The issue is that if you have an interior frame with an X-brace (two columns, a roof beam and an X) wouldn't the roof uplift be somewhat important to include in the calculattions involving the brace...specifically for the footings under the two columns?
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RE: ASCE 7 - Flat roof wind uplift
RE: ASCE 7 - Flat roof wind uplift
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RE: ASCE 7 - Flat roof wind uplift
With 2010 it's 0.6D + 0.6W
Do you think roof uplift is neglected more often than rooftop equipment's effect on the MWFRS, particularly mechanical screens.
RE: ASCE 7 - Flat roof wind uplift
Not sure about screens - We include them all the time.
I think the vertical elements tend to get counted in while my question is more about the horizontal flat roof wind uplift that I think doesn't.
My concern is with any interior wind braces where the roof uplift drastically affects the design of the brace footings.
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RE: ASCE 7 - Flat roof wind uplift
RE: ASCE 7 - Flat roof wind uplift
Can easily be controlling factor in my area! Steel frame with infill light gage is one example.
RE: ASCE 7 - Flat roof wind uplift
1) Anchorage capacity at the tension column base plate and;
2) Frame beam design for a case with high axial load and uplift bending.
During a QC review, I once got challenged for assuming that I could use the entire self weight of the roof assembly to resist uplift. My reviewer felt that, for un-ballasted roofs, I should assume that the roofing assembly above the metal deck might blow off of the roof altogether. He argued that there was no way to guarantee that this wouldn't happen unless I specifically designed the connection of the roofing to the metal deck.
How do others normally handle this? I've always assumed that someone designs the roofing not to fly away. However, that someone has never been me and I've yet to review a roofing submittal where the associated engineering has been presented. My region does tend to be pretty lax about stuff like this.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: ASCE 7 - Flat roof wind uplift
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