10psf wind load
10psf wind load
(OP)
I asked some brief questions about this issue in the past and several of you responded, which I appreciate. I've been challenged on this another way now and would like your feedback.
Is it possible to make the AVERAGE wind pressure equal to 10psf and meet the requirements of Section 6.1.4.1 of ASCE 7? For example, let's say we have a 10' tall building with a 10' projected roof area. If the wall pressure was designed for 15psf and the projected roof area designed for 5psf, would that be acceptable?? Or does 10psf need to be applied uniformly across the entire vertical projection?
Thanks.
Is it possible to make the AVERAGE wind pressure equal to 10psf and meet the requirements of Section 6.1.4.1 of ASCE 7? For example, let's say we have a 10' tall building with a 10' projected roof area. If the wall pressure was designed for 15psf and the projected roof area designed for 5psf, would that be acceptable?? Or does 10psf need to be applied uniformly across the entire vertical projection?
Thanks.






RE: 10psf wind load
This is a moot point though, because I believe there is a 10 psf minimum for the projected area of the roof anyway, when E through the end are zero.
Mike McCann
McCann Engineering
RE: 10psf wind load
akastud
RE: 10psf wind load
For MWFRS:
"The wind load to be used in the design of the MWFRS for an enclosed or partially enclosed building or other structure shall not be less than 10 lb/ft^2 multiplied by the area of the building or structure projected onto a vertical plane normal to the assumed wind direction."
So splitting up the wind as 5psf on the upper part of the projection and 15psf on the lower does not seem to me to meet the intent. What if you concentrated 100psf in the first 2 feet and applied 0psf over the rest of the frame. Would that seem acceptable?
RE: 10psf wind load
Mike McCann
McCann Engineering
RE: 10psf wind load
RE: 10psf wind load
DaveAtkins
RE: 10psf wind load
Doesn't sound like we are. What recourse do we have? We are going to be priced higher because we're following the codes/standards, and our competitor isn't, and he's going to get the job. I'm not going to bend rules just to get a job, but an unlevel playing field is no fun to play on. That is why I want to make sure I'm thinking about this section of the standard correctly.
Haynewp took my proposal to the extreme, which really helps flush out how best to look at it, and really points to the fact that it probably ought to be evenly distributed from top to bottom.
Thanks again for each of your posts!!!
RE: 10psf wind load
I have done a lot of one story wood structures, and usually "standard" construction (1/2" or 5/8" OSB on the roof, 7/16" OSB on the walls, nails spaced at 6/12) is sufficient.
DaveAtkins
RE: 10psf wind load
Most often these are steel-clad wood diaphragms. We're talking lots of stitch fasteners and supplemental chord force fasteners to keep the building from ripping apart!
That is why this is such a big deal. Also, there is the need for a lot more shearwalls on the end bays or the need for intermediate shearwalls, if possible.
Thanks.
RE: 10psf wind load
DaveAtkins
RE: 10psf wind load
Thanks for your response.
RE: 10psf wind load
It's really unfortunate but there are many engineers and firms that will allow deliberate disregard for the code requirements. To further agitate the issue, in many cases, the building officials don't care about enforcing code as long as an engineer is taking responsibility. I have had many conversations with building officials about my interpretation of the code, which they have agreed with, but they also said that when an engineer wanted to overwright the code and seal a different requirement, that it is ok. Obviously this isn't for every code requirement but it happens on ones that can be open to interpretation. Whatever you choose to do, feel good about having sound engineering practices - and a conscience.
RE: 10psf wind load
My only other suggestion would be to consider dividing the building in half, and treating the roof like two separate three-sided diaphragms. This makes the chord forces go away, but now the walls which are perpendicular to the wind load direction must be designed as shear walls.
DaveAtkins
RE: 10psf wind load
I'm not sure I follow how the chord forces go away Dave. Are saying to cut the building in half so that my roof diaphragm is cantilevered off of my end shearwall???....or are you saying split the building lengthwise along the ridge?? Either way, I still have chord forces to contend with don't I? Maybe I'm not following correctly.
RE: 10psf wind load
RE: 10psf wind load
That makes sense. I'm not sure I want to try and analyze that, but I see where they're going now.
RE: 10psf wind load
Maybe, in the end, this is one of those clients that you just can't work with.
DaveAtkins
RE: 10psf wind load
Maybe your competitor is using teh IRC to design these structures. I know sometimes when i look into an engineered design of a single story building it is very expensive. But when i use the IRC or prescriptive method of construction it seems to just "work out". This could be one option to look at...
RE: 10psf wind load
DaveAtkins