Cantenary forces from batting cage nets

[SandwichEngine]

I feel like I've found a thing that doesn't work the way we've been taught in school.

My company does buildings with batting cage nets pretty frequently. We end up adding huge steel to support the massive loads that the tension cables should be putting on the building. In my example, the batting cages are supported by 80 ft cables that support netting that weighs 10 plf and will be allowed to sag no more than 4 inches. It doesn't sound like much by my calculations and those of my colleagues say this should be loading each end with 24 kips of force.

What doesn't make sense is that the batting cage submittal (attached) says that the cables are only good for 7 kips of tension and should be installed into 2x8 wood material. Also customers routinely tell me of buildings they've done where they just went and installed these after the fact in a building that wasn't designed for it and everything's fine.

I think they're right and I think that these don't truly load the building as much as my cantenary equations say they should.

Am I doing something wrong? Anyone got any ideas?

 

[phamENG]

Are you sure the weight is correct? I was just handling similar mesh at my son's baseball practice. An 8ftx8ft section couldn't have weighed more than 2 pounds.

 

[Celt83]

You cable tension formula looks off at a quick glance. This is from the wire rope guide on sliderulaera’s site:

Edit: your formula looks like it expands to the same expression. Agree with Pham 10plf seems high for this and a 4” drape sounds to tight for the primary cables, I’ve seen the support cables have 1ft+ of drape.

I'm making a thing:

http://www.thestructuraltoolbox.com

(It's no Kootware and it will probably break but it's alive!)

 

[KootK]

At 24 kip, that cable would have about 4' of stretch in it. Do they come back and tension the cable after the net is installed?

 

[Aesur]

Based on the information you provided, I agree with your reaction, however it doesn't seem practical.

I'm not a big fan of these types of systems due to such large reactions, especially when it's a fabric tension structure that the owner/architect wants to attach to the side of a wood building.... that the contractor "does all the time without any sag."

 

[SandwichEngine]

You guys have led me down the right path. My assumed weight of the netting was way too high. From the chart I found, this netting weighs about 1/72 psf which clears up the confusion.

https://www.netsandmore.com/component/content/article?id=253:netting-weight

 

[mijowe]

Are you in an area where ice build-up on the net will add to the load?

 

[SandwichEngine]

Mijowe,

These nets are indoors but also, no ice build up in this region.