ASCE 7-10 Partially Enclosed Structures
ASCE 7-10 Partially Enclosed Structures
(OP)
I have recently been asked to design the foundation for a tent structure. Upon reviewing the tent structure engineering, I noticed they have designed the structure as enclosed. The ends of the structure are partially enclosed w/ equal openings. Based on how I am interpreting ASCE 7, by definition this structure is partially enclosed, however the engineers who manufacture the tent disagree stating that because the openings are equal at each end, it doesn't fit the definition of partially enclosed. I feel they are sum what correct, in that it doesn't fit the definition, but in my opinion it doesn't fit the enclosed definition either. It's this is really a cross between an open structure and a partially enclosed structure. I have attached the structure so you guys can take a look and give me your opinion. Thanks for the help.






RE: ASCE 7-10 Partially Enclosed Structures
RE: ASCE 7-10 Partially Enclosed Structures
BA
RE: ASCE 7-10 Partially Enclosed Structures
RE: ASCE 7-10 Partially Enclosed Structures
RE: ASCE 7-10 Partially Enclosed Structures
RE: ASCE 7-10 Partially Enclosed Structures
On a logical basis, I find it irrational to go with a less punitive classification simply because correlation with a more punitive classification is imperfect. That's not what we do.
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 7-10 Partially Enclosed Structures
One might state that if the wind is perpendicular to the opening that eventually air flow would stabilize within the bldg and the air in-flow would equal to the air out-flow without any buildup of press within the bldg. But what happens when the wind is @ 45deg(or 30deg) to the openings.
What are the contents of the bldg that might result in air blockage within the bldg.
Even with wind perpendicular to the long axis of the bldg I would expect unpredictable airflow and turbulence at the openings at both ends that may affect the structure locally at the ends of the bldg.
Without wind tunnel tests I would try to get an upper-bound solution by checking out the various wind load conditions.
RE: ASCE 7-10 Partially Enclosed Structures
To be open, each wall needs to be 80% open. The structure doesn't have significant openings on all sides, so it is not an open building.
To be partial enclosed, the structure needs to meet two criteria. The first requires the total area of openings in a wall that receives positive external pressure exceeds the sum of the areas of openings in the balance of the building envelope (walls and roof) by more than 10%. Since the structure has equal sized openings on two ends, it is not partially enclosed.
To be an enclosed building the definition is "A building that does not comply with the requirements for open or partially enclosed buildings." So, enclosed appears to be the proper classification.
The commentary mentions an enclosed building may have large openings on two or more sides.
When the wind is blowing toward one of the large opening, the opening in the other end will prevent the internal pressure from building-up inside the structure. If the structure has an internal division that restricts air movement, a partially enclosed classification may be justified.
RE: ASCE 7-10 Partially Enclosed Structures
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 7-10 Partially Enclosed Structures
Robert Hale, PE
RE: ASCE 7-10 Partially Enclosed Structures
Dik
RE: ASCE 7-10 Partially Enclosed Structures
I feel ASCE got this wrong. To consider this a fully enclosed structure is not an accurate classification and they should have a provision in the code for calculating the internal pressure coefficient based on the number of openings per wall and area.
RE: ASCE 7-10 Partially Enclosed Structures
BA
RE: ASCE 7-10 Partially Enclosed Structures
Say the wind is @ 70deg(or 60deg) to the longitudinal axis....I would anticipate a zone(16 to 18ft high) where air seperation could occur behind the windward wall and also the leeward wall...how far that zone extends into the end bays would be a judgement call....it may or may not control design in that area but, at least, I have attempted to address that possibility.
RE: ASCE 7-10 Partially Enclosed Structures
While I appreciated wannabe's able code interpretation, it was really his succinct explanation of the theory that did if for me. And, in a similar vein, Robert Hale's take.
I (now) see the partially enclosed situation as requiring both of the following in order to generate the associated wind pressures:
1) A significant opening through the windward wall through which air can be pumped into the space faster than it leaves.
2) The absence of a comparably significant opening in any other surface of the building through which the air from #1 can escape at a similar rate to which it enters.
This jives with the code provisions nicely. And I contend that it's irrelevant which of the non-windward surfaces serves as the pressure release valve. It could be the roof for all the difference that would make theoretically. Heck, it could be some kind of intelligent HVAC system.
Be careful what you wish for. I, for one, have no desire to see the ASCE wind provisions grow in complexity.
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.