Snow Load on Open Louvers

[Ron]

I am analyzing a louver sunshade awning in a snow area with GSL of 40psf. Louvers have 40% solid, 60% open projection. Louver support is horizontal, louvers are slanted at 45 degrees to shade windows.

Need an opinion as to whether drift load should be applied to this.

 

[3dboy]

yes

 

[MotorCity]

Ron,

I disagree with 3dboy for the following reasons:

1. Because the louvers are inclined at 45 degrees I would not expect significant accumulation at such a steep angle.

2.I assume that they are made of metal which would conduct solar heat and melt the snow and prevent any significant accumulation.

3. Louvers are aligned in a vertical plane. Depending on the spacing of the louvers, any given louver would be protected from large accumulations by the one above it.

4. Its overkill.

 

[3dboy]

If you read ASCE 7 it has provisions for determining the factors you are concerned about (i.e. slip and whether it is heated or not) I think you should apply ASCE 7 and determine whether or not it needs to be accounted for. The code dictates that this is and "unheated" structure and the factor applied to the snow load as such is greater than 1. With a slope of 45 degrees the factor is less than one, but it still needs to be accounted for. If GSL is 40 psf, there is a significant amount of snow. I'm glad that there is a lot of openness, but snow drifts build up over openings. Regardless of all the reasons you stated we have a duty to design per the code.

 

[MotorCity]

I agree that it should be designed per the code, if it applies. The snow loads in ASCE 7 are for ROOFS. Louvers are obviously not roofs, but I would consider them to be components or cladding. The height of snow that would produce 40psf is most likely much greater than the vertical spacing of the louvers.

The openness in the code allows for assumptions and interpretations. We have a responsibility to follow the design codes, but we also are obligated not to follow them blindly.

 

[Ron]

MotorCity/3dboy....thanks for the input. The argument between you was the same one I was having with myself! I've decided to compromise. I'm applying the drift load on the two louver lines closest to the building. The other two are hanging out in space and are not as likely to accumulate snow. Further, the members are elliptical and canted at 45 degrees, further reducing the potential to collect.