WIND LOAD ON SOLAR PANELS?? 2

[damstructural]

I'd like to get some opinions on what wind load values are appropriate for an unusual structure - a large array of solar panels mounted on the side of an embankment. The panels are mounted on a lightweight steel frame, 4 feet off the embankment. With 4 ft of clearance under all the panels, wind can get under the panels. Because its so light, and the structure is already leaning at 26 degs, I need to be concerned with overturning stability.

I've calculated wind pressures using my best judgement with the CA Building Code (Based on UBC97), and with ASCE 7 "simplified" method. There is nothing in the code that applies directly to this situation. What is your opinion?

Thanks.

 

[damstructural]

A little more detail:
The local jurisdiction (UBC) requires 80mph Exposure C. The panels extend along the entire side of the embankment, which is 40 feet from the top to the bottom. The array is 500 feet laterally along the embankment. Its a large project. The design utilizes grade beams for dead load to prevent overturning.

Thanks in advance for your opinion.

 

[DaveVikingPE]

I don't think that the simplified method of ASCE 7 would be applicable - only because I'd use if for buildings exclusively.

This comes to mind: these are "signs" or "freestanding walls" and should be designed regarding wind using method 2. It also sounds like a pretty ambitious undertaking; have you considered wind tunnel studies?

 

[damstructural]

I'm actually a reviewer, not the designer. I raised the uplift/overturning issue at my first look at 90% design. They came back with very minor improvements for the 100% P&S and now they want to start construction. The designer seems to be trying to "beat" the code rather than "meet" the code. I'm looking for other independent opinions, especially for Ce and/or design uplift pressure. I've found some wind tunnel testing and computational fluid dynamics work, but the configuration has a dramatic effect on the lift that is generated, so I'm not sure how to apply it for this situation. I'll be making lots of calls on Monday.

Thanks, David. I hope others weigh in, especially if they have relavent experience or know where to point me for good advice.

More Detail:
Each array is mounted on an independent frame with 2 grade beams/strip footings running up the slope for ballast, so the structural calcs pertain to 26 ft width and 40 ft length on a 26 deg slope.

 

[JAE]

Yes, DaveVikingPE is correct - you'd use the "signs" part of the wind provisions. These are not buildings.