2 Column Canopy Roof Question
2 Column Canopy Roof Question
(OP)
I am in the preliminary stages of designing a 2 column cantilevered canopy (similar to what you see in small gas stations) and what is discussed here: http://www.eng-tips.com/viewthread.cfm?qid=232846.
I noticed looking at pictures of similar structures and by using satellite images from a few around my area, most appear to be designed with the framing exposed and a roof deck fastened to the bottom side of the framing. Closer inspection from the ground shows downspouts running down through the column.
Two questions:
One, is this typical to leave the steel framing exposed without any decking or roof membrane above it? If so, why? I would expect that you would want to fasten the decking/membrane material above the framing as with other roof structures.
Two, some articles I have read suggest that running downspouts through the column allows the possibility for water to collect at the base of the column and corrode the member. This makes sense to me. Are the examples I am seeing simply outdated and are newer structures typically built with downspouts fastened to the outside of the column?
Thanks!
I noticed looking at pictures of similar structures and by using satellite images from a few around my area, most appear to be designed with the framing exposed and a roof deck fastened to the bottom side of the framing. Closer inspection from the ground shows downspouts running down through the column.
Two questions:
One, is this typical to leave the steel framing exposed without any decking or roof membrane above it? If so, why? I would expect that you would want to fasten the decking/membrane material above the framing as with other roof structures.
Two, some articles I have read suggest that running downspouts through the column allows the possibility for water to collect at the base of the column and corrode the member. This makes sense to me. Are the examples I am seeing simply outdated and are newer structures typically built with downspouts fastened to the outside of the column?
Thanks!






RE: 2 Column Canopy Roof Question
I don't know where the ones you looked at are, but if snow load controls, the deck may be figured to provide lateral stability for the compression flange.
I used cellular deck on the top flange, that would span from support to support. It was covered with shaped fill and an elastomeric membrane roofing. The shape of my supports was a modified "T" with a slight slope and toward the center and crickets to aim the water at the drains.
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: 2 Column Canopy Roof Question
RE: 2 Column Canopy Roof Question
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: 2 Column Canopy Roof Question
Any particular reason why you leave the framing exposed?
RE: 2 Column Canopy Roof Question
Not that I agree with it. It's a huge snow collector in my opinion. Putting a standard roof is not the norm unless the owner or architect is aiming for that look.
RE: 2 Column Canopy Roof Question
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: 2 Column Canopy Roof Question
Do a quick bing images search for " gas station canopy collapse". As stated before, this is also antecdotal, but my preference is to design the downspout outside of the column if at all possible. The concern that I always have is that if the owner is pushing for the absolute cheapest solution, there approach to maintenance such as painting, downspout repairs, etc. will follow the same path.
RE: 2 Column Canopy Roof Question
Despite being the cheap alternative, I believe I will most likely propose to do some sort of decking above the framing. I need to check some estimates, but I can't see it adding a whole lot to the project for the size of canopy I am working on.
In consideration for the maintenance at this facility as it is, I am very wary of putting the downspouts through the column. It seems like an unnecessary risk since the owner will probably not care about seeing downpouts.
Thanks again for all of the help.
RE: 2 Column Canopy Roof Question
RE: 2 Column Canopy Roof Question
Here is proof: http://www.youtube.com/watch?v=voTYHtezv4I
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: 2 Column Canopy Roof Question
RE: 2 Column Canopy Roof Question
Sure you asked about conc. protective bumps, but I'll bet you never designed the catching system on the other end. If the design shown is similar to your design, were you assuming they could charge a higher toll if the car went through the gate airborne?
RE: 2 Column Canopy Roof Question
Michael.
Timing has a lot to do with the outcome of a rain dance.