Stainless Steel Cable Railing Design 2

[STrctPono]

Does anybody have experience with designing a stainless steel cable railing? I'm working on some for a golf course and everything that I come across seems to be really geared toward the residential DIY'er and supplied in kit form. I think that I'm getting bogged down with all these online suppliers and what I really need is a custom built system. I was out the other day and took these photos of a cable railing system. Not a kit, looks custom built, more durable, seamlessly welded and ground down flush, and more geared to what I think should be specified for a commercial application. However, I believe that that corner detail does not satisfy the 4" sphere requirement. So many of these kits seem to have these cheap top rails that just snap into place.

I understand the geometric constraints, want to use 3/16" dia. cable, 2"x2" post and top rail, and will have a custom mounted rub rail at the base to act as a golf cart bumper. I can handle the design of the terminal posts and base plate connection to the deck. I need to familiarize myself a little more with how to specify the hardware and tensioning at the terminal post connection.

Any experience from other Engineers with designing these for commercial applications? I could use some help steering me in the right direction.

 

[BridgeSmith]

Not sure what aspects of the design you're concerned with, but I'll offer what may be a fairly obvious bit of insight: Neglecting gravity, which is negligible in this case, the deflection of the cable is fairly straightforward as a force vectors - force in the cable = lateral force on the cable multiplied by the distance from the force to the support point divided by the deflection of the cable. So if the cables are 3" apart, the post spacing is 100", and has to resist a 4" sphere being pushed through with 10 lbs of force (I have no idea what the design force for that is), the required tension is 1000 lbs (each cable deflects 0.5", with a max assumed distance from the post of L/2 = 50" ---> 10lbs*50"/0.5" = 1000lbs.



Rod Smith, P.E., The artist formerly known as HotRod10

 

[XR250]

Rod,

Doesn't that assume that the cable is infinitely rigid? What about the case when it is made out of spaghetti? It will easily deflect the .5" without a 1,000 lb tension.

 

[XR250]

Actually, what you said does make sense if it is to keep the ball from being pushed thru the opening.

 

[Ron]

This type of railing (with horizontal members) was at one time prohibited by the life safety code (NFPA 101). That prohibition was taken out at some point ( I believe early 2000's).
That doesn't change the reason for the original prohibition which was to prevent little climbers from climbing the rail and falling over, sometimes to their death (has happened numerous times on mid-rise and high rise buildings in Florida.

I have turned down railing designs where a horizontal member above the 2" toe kick and below the top rail was desired. Too much liability.

 

[BridgeSmith]

Doesn't that assume that the cable is infinitely rigid? What about the case when it is made out of spaghetti? It will easily deflect the .5" without a 1,000 lb tension.

Actually, what you said does make sense if it is to keep the ball from being pushed thru the opening.

That's what I was trying to get at. As I understand it, the cable railing has to keep a 4" sphere (representing a child's head) from being able to push through between the cables. I was attempting to describe a method to determine the required tension in the cables.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[IRstuff]

You could go with a rod railing, instead of cable, which would obviate the wire tension and tensioning during installation. The only snap-on, or more likely, push-on handrails I've seen were for glass railings.

Most of the steel railing handrails I've been looking at are screwed onto the capping of the posts.

https://www.stairsupplies.com/product-category/rod-railing/

https://www.viewrail.com/rod-railing/

These sites supposedly will work with you and your design and ship you the entire kit; I'm not sure what the cost difference would be compared to the piecepart cost.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

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[IRstuff]

Both of the above sites also sell cable railing kits and parts and they detail how to get sufficient tension on the cables to meet code. Given that complication, the rod railings would seem to be an easier thing to deal with, since they don't need to be tensioned.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[STrctPono]

Rod,

Thanks. That actually does help. Most of them are tensioned to say 300 lbs for a 5/32" cable. Breaking force for cable is far beyond that but I don't want to overspecify the tension as it requires designing the terminal posts for the load.

Ron,

I too don't like the design. I tried very hard to get the owner to go with several other different types of railings. In the end, the board members of the golf course wanted it as open as possible for visual affects. Putting my feelings to the side regarding the railing type, if I am forced to design this type of railing, I at least want it to be correct and something that is going to last. This will be installed directly adjacent to the ocean.

IRstuff,

The example companies you sent were exactly what I am having issues with. You don't find those cheap and flimsy looking? The top railing gets connected to the bracket via some self tapping screws. Crevice corrosion looks to be very problematic with the bracket detail. They also use plugs at the ends of the top rail and all joints are merely miter cut and butted together. How is water intrusion not a huge issue? Don't get me wrong, if I was installing this by myself at my house I would be very happy that it existed but I would never even consider it for a municipal owned project and I am seriously questioning it for a private commercial job.

 

[IRstuff]

That'll be the 2x price ratio, primarily for the welding/labor.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

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[dik]

The solid round bar material would likely bend over time, cables won't.

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

-Dik

 

[straub46]

Try the Post-Tensioning Institute, Tech Note 14. It gives an idea of design loads and deflection/sag requirements.

https://www.post-tensioning.org/education/publications/faqstechnotes.aspx

Go Bucks!

 

[STrctPono]

straub46. Thanks for the reference. That does help.

IRstuff. You're right. The price will be more. Unfortunately, the cheap-skate Contractor that was brought on board already gave the Owner a price based on these kits. So if I change it at this point, it's going to create an issue. I'm debating at this point if I hate the kit system enough to create an issue and paint myself in a bad light, knowing that it will be better for the Owner in the end.

Am I the only one that thinks these pre-engineered systems look cheap?

 

[hotmailbox]

Pages 50 to page 54 in this calculation.

https://www.crlaurence.com/datasheets/testreports/docs/crl7.pdf

 

[dik]

Let them know that the certification of the railing has to be by the supplier, and leave it at that. Is there an architect involved? Maybe he has some sway... There's an ugly 6 storey building down the street from me that I designed 50 years back... I told the developer that he should hire an architect because my aesthetic skills are zip... no such luck.

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

-Dik

 

[dik]

hmb... good document...

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

-Dik

 

[bridgebuster]

If you're still in need of design info, try Ultra-tec. I came across some of their technical info in my files today.

Link

At the bottom of the page under Engineering Data there's a link to calculations for various code diameters for pass-through resistance for 4″ sphere.

 

[STrctPono]

hotmailbox and bridgebuster, Thank you for the links. These do help with design info.

 

[bridgebuster]

STrctPono - you're welcome. I'm glad it was helpful.

 

[hotmailbox]

STrctPono - I have been asked by plan checkers to provide calculations for railings in all projects and each project is different. And this typically takes a lot of time. I was in your situation before and I found it very helpful too. You're welcome.