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Wind on Walls of Low Rise Buildings

Wind on Walls of Low Rise Buildings

Wind on Walls of Low Rise Buildings

(OP)
Is there any software that computes wind pressures/suctions on walls of low rise buildings, and computes the corner effect widths "y" and "z" in accordance with the User's Guide to the National Building Code of Canada 2010? I see software on the internet that computes wind pressure/suction of low rise building roofs, but does not do walls; and there is software on the internet that does walls, but does not compute the "y" and "z" values, unless I missed them.

RE: Wind on Walls of Low Rise Buildings

(OP)
Sorry, I see that there is software from NRC that does give the corner effect widths ... but "y" dimension seems too small...I will study it further...

RE: Wind on Walls of Low Rise Buildings

Probably easiest to make a Mathcad or excel sheet that does this. I'm sure PEMB guys have proprietary software to do this for their structures though.

RE: Wind on Walls of Low Rise Buildings

(OP)
thanks, but who is PEMB?

RE: Wind on Walls of Low Rise Buildings

Pre-Engineered Metal Building...i.e. "Butler"-brand buildings and the like.

RE: Wind on Walls of Low Rise Buildings

Bit off topic, but the comment that y can just be taken as the bay width in the commentaries was basically done to make their lives easier. Although computers do most of their design nowadays anyway.

RE: Wind on Walls of Low Rise Buildings

I prefer PMMB. (pre-manufactured metal building).

Every building on earth are, or at least should be, pre-engineered.

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RE: Wind on Walls of Low Rise Buildings

I was informed recently that PEMB's are now being referred to as SBS's (Steel Building Systems). Apparently they are so customized and engineered for economy on a project by project basis that the idea there are a stock 'pre-engineered' designs on the shelf is a thing of the past.

ajk1, have you checked out the jabacus website? www.jabacus.com

RE: Wind on Walls of Low Rise Buildings

They'll try and sell pretty much anything, since they can fab all kinds of stuff. The real economy is in the standard PEMB shed, no way we can compete with that.

RE: Wind on Walls of Low Rise Buildings

(OP)
To Canuck67 - yes I did look at jabacus before I posed the question here; that is the site that gives the wall pressures and suctions but does not give the corner dimensions for the width of higher pressure/suction. They seem to have done only part of the job? Strange, since the pressures cannot very well be used without knowing the width over which they apply.

RE: Wind on Walls of Low Rise Buildings

The end zone determination calculation is super short and easy. Create your own spreadsheet if you're unable to quickly run the calc.

RE: Wind on Walls of Low Rise Buildings

(OP)
There seems to be something very wrong with the internet "Jabacus" wind load calculation. The problem is that the values they list are in a column headed "ULS", but they are actually unfactored. In other words, when I calculate wind pressure = Ci Ce Cp Cg q50, where q50 is taken from the NBC climatic data chart, that gives an unfactored load. To get the ULS (Ultimate Limit State) those loads must be multiplied by the 1.4 load factor for wind. I get the exact same numbers as Jabacus, but they are NOT ULS, they are unfactored. Or am I wrongly interpreting something?

RE: Wind on Walls of Low Rise Buildings

They give you the full 1.0 ULS value. Which load combination factors are used depends on the loading conditions and which combination results in the worst case.

The SLS value has a different Iw than the ULS value. For wind Iw is 0.75 for all building categories. For ULS it ranges from 0.8 to 1.25.

RE: Wind on Walls of Low Rise Buildings

(OP)
To jayrod: Yes thanks. I eventually figured out that what is meant is only that Iw=1.0 corresponding to the ULLS value for Iw is included. But that is an incorrect and dangerous way to present the results, because ULS means that the load has been multiplied by the load factor. One would not likely know that it has not been multiplied by the load factor unless one worked it out manually and compared the results. I am now dealing with an architect/engineer (yes he is both) who interpreted the tabulated values as including the load factor. The author should correct the heading by removing the "ULS" from the column heading, and replace it with the formula p=Iw Ce Cp Cg q and that Iw=1.0 Either that, or there should be a note saying the tabulated values must be multiplied by the appropriate load factor as given by clause ....of the Code.

RE: Wind on Walls of Low Rise Buildings

I think it would be incorrect to give it with the load combination factor applied. Because they don't know what load combination you are looking at.

So I'm inclined to say that the program is spitting out the correct number it should be. Maybe they need to have a disclaimer that the load combination factors still need to be applied to the design pressures they give.

RE: Wind on Walls of Low Rise Buildings

I would agree with the way it is presented in jabacus. It is clear to me and then you factor it from there. Both the ULS and SLS need to be factored in different manners depending on your situation.

RE: Wind on Walls of Low Rise Buildings

(OP)
To Jayrod12 and Canuck67:

I appreciate your comments, but sorry, I must respectfully disagree with you both. ULS has a specific and clearly defined meaning in structural engineering, at least it has in my 50+ years of structural engineering. The values in that table are not ULS values, and therefore ought not be labelled as ULS. I agree with you that the load factor should not be applied because it is a different load factor for companion loads, but I never suggested that it should be. That is why I said that the (incorrect) title should be changed, not that the values should be multiplied by a load factor. The change that I suggested would make everything clear...which has always been my goal when serving on technical committees.

RE: Wind on Walls of Low Rise Buildings

Respectfully, please explain how they are not the ULS values. They give you the W value that you plug into the load combinations. That's precisely what I'm looking for.

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