Snow collection area? 1

[SteelPE]

We are looking into a building that is on a rather small sloped site. Parking for the building is difficult therefore there is a proposal to put the parking on the roof of the building. The building is located an area of the country that receives snow.

The question is in regards to snow collection areas (where the snow is pushed by plows). Is there a code provision that tells you how much snow you can expect in these areas? I haven’t really found anything yet, the little information I have found just states that consideration should be given for such areas

 

[ToadJones]

Even if there were a code provision, I would not trust it.
I used to work at night plowing snow. We'd pile it as high as we could anywhere we could put it during bad snows. The piles of snow would be 10' tall and sometimes soaking wet.

 

[mbullism]

The MA code makes note of such areas, but only says that you have to give them due consideration. I've never seen a specific methodology...

 

[SteelPE]

OK then, I guess the question now comes into what "due consideration" I should give them? 100psf, 200psf, 300psf, 500psf?

 

[H57]

I am not aware of any specific code provisions, but a couple things that you may consider:

1) What is the total design weight of snow on the parking area.
2) What is the designated dump area for the snow.

The above could give you a starting point for deck load. In addition to the above I would consider:

3) What is the maximum height that they can plow the snow.
4) Given the compressed thick snow it will not melt as much between snows, so how much accumulation of snow could you see.

Where I live there are code provisions requiring the posting of a snow removal plan for the top level of parking garages. Along with this the structure must accommodate the removal plan and snow storage. I have not had to design a parking garage, but I could see myself following the above logic and adding factors until I became comfortable.

 

[SteelPE]

H57,

I do agree with your approach but I’m not sure I would ever be comfortable pinning down an exact number. Obviously to be conservative I could use the density of water for the density of snow (62.4pcf). This would account for the melting/freezing cycles in-between snow storms. This assumption may not be valid if you consider them applying sand to help with traction.

This is very preliminary at the moment. We don’t even know where the collection areas will be. I’m just trying to get ahead just in case we get the job.

 

[H57]

I understand and am looking forward to input from others who have experience in this. Given documentation requirements there has to be some sort of guidance out there.

 

[rb1957]

you're talking about plowing the snow that's on the (car-park) roof ? could you loose some car parking spaces to account for the snnow piles ??

 

[SteelPE]

rb1957,

You are correct. They will have to plow the snow into a designated area and more than likely loose a few parking spaces.

I take it you have never bee in the north after it snows. Sometimes the snow is piled 20' high (depending on what machinery they are using). Obviously in this instance there is going to be a limit.

Unfortunately the required loading for a parking area (for passenger cars only) is 40-50 psf. Which is about with the roof snow load is before you consider plowing.

 

[ToadJones]

Ask the owner if he wants to go with a snow-melting machine.
I have seen municipalities turn to this when bad winters lead to giant snow pile-ups.
Sounds far-fetched, but might save money when compared to a floor with a 1000 psf live design load

 

[DaveAtkins]

Most of the parking ramps I have seen have an opening on the upper level to push the snow through--usually into the open area in the middle of the ramp. The snow piles up in the open area, on the ground, and never becomes a load on the upper level of the ramp.

DaveAtkins

 

[rb1957]

we sometimes get snow here, north of the 49th

so you could use 50 lb/sqft over the roof, concentrated into a smaller area, and reinforce the roof.

i also thought about a heated roof (an anti-snow measure) ... maybe pray for global warming !

 

[SteelPE]

rb1957,

I thought about heating the roof as well.... however, I don't think the "tree huggers" would like that to much.

Interestingly enough, we are currently faced with an energy code change in the jurisdiction as well. We need to provide an R30insulation under the parking deck. This only adds to the problem.

 

[SkiisAndBikes]

North of the 49, I have seen several examples in two or three storey, above grade parking structures where a pickup truck with plow is used to move the snow to one corner/edge where there is a gate in the parapet. Each snowfall the deck is plowed and the snow is dropped to ground level in a designated area, on grade. Bollards are in place in the opening to allow the snow to pass through the opening but not the pickup truck.

Alternately, I have also seen a small front end loader used to pick up the snow and dump it over the parapet, to ground level. The snow pile is then pushed/trucked away, as required.

I have only seen 1 or 2 snow melters in place, very few relative to the other options above.

I have yet to review a set of structural drawing for an elevated parking deck that notes additional design live loads for the piling of snow. That certainly doesn't mean they don't exist, however, it may be an indication that it is preferable to allow for the removal of the snow, rather than design for additional capacity. I can think of several situations where the removal of snow may not be practical.

skiisandbikes