Wind loading on low rise buildings with large openings at gable ends
Wind loading on low rise buildings with large openings at gable ends
(OP)
All
We are often asked to design industrial portal frame buildings for use as loading facilities for trucks etc. Typically these are long rectangular single story buildings with gable roofs or similar. They are fully clad along the side walls and roof but fully open at both ends to allow the trucks to drive in and out.
Due to the large openings we have typically treated both side walls as "windward" as a conservative approach to allow for wind that may hit the building slightly off perpendicular to the side walls (ie cross wind). Although there would certainly be some shielding from the first wall we often dont account for this.
I would like to improve on this design method and would be interested in hearing how others treat these type of structures for cross wind loading.
Appreciate any feedback/ advise
We are often asked to design industrial portal frame buildings for use as loading facilities for trucks etc. Typically these are long rectangular single story buildings with gable roofs or similar. They are fully clad along the side walls and roof but fully open at both ends to allow the trucks to drive in and out.
Due to the large openings we have typically treated both side walls as "windward" as a conservative approach to allow for wind that may hit the building slightly off perpendicular to the side walls (ie cross wind). Although there would certainly be some shielding from the first wall we often dont account for this.
I would like to improve on this design method and would be interested in hearing how others treat these type of structures for cross wind loading.
Appreciate any feedback/ advise






RE: Wind loading on low rise buildings with large openings at gable ends
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Wind loading on low rise buildings with large openings at gable ends
RE: Wind loading on low rise buildings with large openings at gable ends
Fairly often such buildings are in relatively open areas and should be designed under Exposure Condition "C", not "B" as is often used, keeping in mind that if any upwind direction has 600 feet or more of unobstructed space, then "C" must be used. Obviously, design for the condition now, not what might be in the future.
Your approach is probably overly conservative. Do your analysis with the wind "face on" and oblique and you'll see the actual difference. You might be overdesigning by 30 or 40 percent.
RE: Wind loading on low rise buildings with large openings at gable ends
RE: Wind loading on low rise buildings with large openings at gable ends
Apologies to the OP for assuming!
RE: Wind loading on low rise buildings with large openings at gable ends
Thanks
RE: Wind loading on low rise buildings with large openings at gable ends
so this leaves the 22.5-77.5 which is up for grabs, I I would suggest you read- Holmes, J. D. (2000) 'Wind loading of parallel free-standing walls on bridges, cliffs and embankments', he also talks about it in his book, "wind loading of structures".
He shows that with closely space free standing walls you have a reduction in the Cpe. he also show that a elevated compared to a non-elevated wall there is an 80-90% difference in the loading, thus I think the roof would also reduce the Cpe from a free standing wall n ground. thus I normally use engineering Judgment based on the length of the building and spacing of the walls and a roof reduction, however normally give the walls are very closely spaced compared to height for the truck stop, I find the worst case is as defined by the code for cross wind however the main conservative step I take is I adopt a higher Kl than required by the code.
However to get some real advice as to the interpretation of the code send John H (or Cam Leitch/John Ginger from JCU) an email, they all are normally very helpful. Well I wouldn't mind knowing the answer as well so I might send him an email for kicks.
Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it
RE: Wind loading on low rise buildings with large openings at gable ends
Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it
RE: Wind loading on low rise buildings with large openings at gable ends
Initially, I read too much into the OP's post here.
Nevertheless, check ASCE 7-05, 6.2 under "Building, Partially Enclosed", specifically the latter portion of note 2.
I do not know the dimensional particulars of the OP's building here, but the way I read the note is that if the sum of the two endwall areas is 20% or greater of the total wall area of the structure, then it defaults to an open structure. If not, then it is partially enclosed.
Please correct me if my interpretation is incorrect.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Wind loading on low rise buildings with large openings at gable ends
The default, if it doesn't meet the criteria for a partially enclosed building, is an enclosed building, not an open building (see commentary on 6.2). Further, the intent of defining an "opening" is one that only receives positive pressure.
Ron
RE: Wind loading on low rise buildings with large openings at gable ends
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Wind loading on low rise buildings with large openings at gable ends
Large openings on the end walls could contribute to internal pressure which might affect the design of cladding and roof structure but would not affect the lateral force on the portal frames.
BA