Wind pressure on netting

[gasma1975]

Hi,

I have to design a baseball backstop net structure. Total height is 60 feet. The first 16' feet is a chain fence 2x2 ga #6 (0.192'' dia.) and the rest will be a nylon net.

My client is asking for a free standing pole. I'm not sure how to determine the wind pressure on the net. Is it just an area ratio of what goes through versus a solid sign ? Because if I use this approach, I get 34% for the chain link fence and 14% for the nylon net and its still a lot of pressure on the pole.

How do you calculate the pressure on the net ?

Thank you,

gasma1975

 

[bugbus]

I have had to design a few safety fences with welded wire mesh. I would say that my experience overall is somewhat limited and based on Australia standards.

There are generally two ways to calculate the drag force on the mesh/screen/netting/etc. (1) Design as a solid hoarding or wall and apply some sort of empirical reduction factor for porosity. (2) Calculate the drag acting on individual elements of the mesh/screen/netting and sum these to give the overall effect.

If the open area of the material is high enough (>80%), I found that there is not much difference between the two approaches.

For relatively dense material (open area <50% say), approach (2) above does not account for the interference of flow between adjacent wires and tends to underestimate the total drag.

Also, approach (1) above I found to be slightly conservative overall, especially for wire mesh, since it is intended to be broadly applied to any sort of porous screen or hoarding, which would include perforated sheet metal and the like, which does not have the benefit of smooth, rounded wires.

I imagine that for netting, there is an added complication that the drag would also depend on how tightly it is stretched.

I have a lot papers on drag of mesh/netting/perforated metal/etc. that I can share if you like.

 

[dik]

From a spreadsheet I picked up a few years back... I don't have a copy of ASCE to know what the references are.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

Also found this tucked away on the HDD... I'd post the spreadsheet, but I don't know the source... the scourge of some tekkie packrats...


Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Settingsun]

https://chainlinkinfo.org/technical-information/

This site has a document called the Wind Load Guide. It seems to use a simple solid area ratio.

60' is a lot so it stands to reason the post will be larger than some people's expectations.

 

[3DDave]

Include the effect of wind if there is freezing rain accumulation.

 

[gasma1975]

Thank you all for the help, the spreadsheet was very useful !