Live Roof Load for Parking Structure

[smcp4blo]

Hello everyone,

I have a question. The structure I'm designing is a typical roof structure for parking lots with a 5° slope in a flat terrain, the purpose is to provide shadow with photovoltaic panels on the top so they can generate energy. I'm having difficulty picking the correct roof live load for this structure with ASCE 7-10, since it says on table 4-1 it is 20 psf for flat, pitched and curve; but it sounds like a lot since no one ever is going to be on top of these, except maybe a worker. I'm more interested in picking 5 psf, like awnings and canopies, or Screen enclosure support frame types.

Any comments?

The thing is, for more weight more heavy is the structure and it costs more, and on the other hand, the critical issue for this structures the overturning so less weight is kind of safer for me since i'll have bigger uplifts and I can provide a better foundation.

Thank you

 

[EngineeringEric]

What is the snow ground load in the area. There is a good chance you may be looking at 20 psf in which case the reduced live load is trivial.

I would do 20 psf live load. How many people do you see on roofs, ever, and they are typically designed for 20 psf. The increase in structure is bound to get cancelled by the LEED Tax credits, No?

 

[smcp4blo]

Sounds like you are right, the snow load is 15 psf, so live load looks similar.

 

[EngineeringEric]

Sorry to be the bearer of bad news.

 

[JedClampett]

There's also a downward wind component that might control if you're in a higher wind area (windspeed >110 mph).