4 Sided Open Roof Top Signage Wind Loading
4 Sided Open Roof Top Signage Wind Loading
(OP)
I have a project that involves placing a 4 sided sign, open top and bottom, onto a building. It forms a 10'x 10' cube, is located at a building corner, and slightly overhangs a 3 foot high parapet on one side. The building it is situated upon is a 5 story hotel (<60 ft mean roof height). The question is: what wind load procedure would you apply to it per ASCE 7-10? Do you analyse it as a roof top structure, a parapet (extension), a free standing sign - something else?
The open nature of it, as well as its overhanging condition is a bit challenging. It is one of those conditions that is rather unusual and not addresses specifically in the ASCE 7 code (no great surprise there). My current approach is to look at it using each ASCE 7 design case, then design it and its supports for the most conservative values, however, that really doesn't answer my question of how it "should be" viewed for design. Its seems pretty subjective. I am curious as to how others would view this?
The open nature of it, as well as its overhanging condition is a bit challenging. It is one of those conditions that is rather unusual and not addresses specifically in the ASCE 7 code (no great surprise there). My current approach is to look at it using each ASCE 7 design case, then design it and its supports for the most conservative values, however, that really doesn't answer my question of how it "should be" viewed for design. Its seems pretty subjective. I am curious as to how others would view this?






RE: 4 Sided Open Roof Top Signage Wind Loading
Dave
Thaidavid
RE: 4 Sided Open Roof Top Signage Wind Loading
For your case I think the rooftop structure or an extended parapet would get you close to "reality".
I would guess that the technically correct answer is that if ASCE 7 doesn't directly address a condition you should look at wind tunnel testing.
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RE: 4 Sided Open Roof Top Signage Wind Loading
I agree with JAE that this is not a case for sign loading. I disagree that wind tunnel testing should be performed. It certainly could be, but I don't believe that wind tunnel testing is required if a structure doesn't exactly fit into any of the categories defined in ASCE 7. For a small building appurtenance like this, nobody is likely to want to pay for a wind tunnel test. That would be beyond industry standards in my experience.
RE: 4 Sided Open Roof Top Signage Wind Loading
thaidavid40: I don't want to be too conservative on my approach here, and I think C&C might push me into that area. I didn't mention it, but this is a wood building (4 levels of wood over podium). Too conservative (high) a loading will have unwanted impacts.
Thawkes: I can confirm your thoughts regarding wind tunnel testing. The owner would never pay for it. And i agree the true load is likely somewhere in between a rooftop structure and a parapet, as you mention.
As an aside note here, this particular hotel chain has these cubes on all their building in Europe. However, each example of these hotels, say about a dozen, shown to us by the owner, were all of concrete and steel construction - no wood. I would have no problem really loading up this cube with either steel or concrete construction. The wood part is really the crux of my loading issue.
RE: 4 Sided Open Roof Top Signage Wind Loading
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