Wind Pressures on Louvers

[WeezerMike]

Hello out there.

I am currently trying to solve a problem with a rooftop mechanical screen. Long story short, we are committed to a roof screen system (panels, frames, connections to structure, etc) that is not adequate to resist full code level wind pressures on solid panels. Thus, we are looking to switch to louvered panels to reduce the pressures and make our system a viable option.

ASCE 7-05 section 6.5.2.2 states full wind pressures shall be used "unless approved test data or recognized literature demonstrate lower loads for the type of air permeable cladding being considered".

Thus, I am in need of some testing or reports that address wind pressures on louvered systems. So far I tracked down information from the company 'Architectural Louvers' that offers reduction coefficients for their specific louvers, but I am looking for something with broader application so that I am not tied to one louver manufacturer. Any input or references you have is greatly appreciated.

Thank You!
-Mike

http://www.archlouvers.com/Equipment_Screens.htm

 

[Ron]

You might want to consider them not being "air permeable cladding". To do this, make sure each louver is an independent, fixed member. Then apply appropriate wind coefficients to each and analyze independently.

I have designed some large "louver" systems where the individual louver blades had to act as structural members.

If your louvers have screens behind them, then you'll have to design as air permeable cladding.

 

[MiketheEngineer]

Agree with Ron. And unless the mfg has tested their own louver - I think you are SOL.

 

[msquared48]

Note too that Ron said "FIXED" louvers.

If they are moveable, the assembly will have to be designed as a solid wall as they can be closed as well as open. Worst case scenario governs.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[JedClampett]

I've had occasion to calculate the pressure drop through a 16 mesh screen in support of tank vent design. There are two good references for losses through shapes. One is by Idelchik. I can't remember the name, but I doubt there's that many books by him. But the better, more common book is an ASHRAE Design Handbook. Lot's of boring entropy and enthalpy stuff in the beginning, but the last 50 pages or so are all pressure loss coefficents for common HVAC parts. I don't have the book with me, but I suspect they have every type of louver there is.