Handrail post connection detail 1

[cliff234]

We are developing a handrail anchorage detail where 2" steel handrail posts will plug 4" into 4" diameter pipe sleeves embedded into concrete. Grout will be poured into the sleeves to secure the posts. The 4" sleeves will be positively anchored. My concern is the bond between the grout and the post and between the grout and the sleeves. If the grout, or the bond between the grout and steel fails, then the posts will come loose. I see connections of this type used frequently, however I am concerned about this detail because we are only have 4" embedment and this handrail is on a balony high up on a building. I would prefer a mechanical connection, but our client prefers the detail I described. Are there epoxy grouts suitable for this application that will reliably bond to steel and will withstand exposure to weather without failing or debonding?

 

[haynewp]

Isn't this just bearing of the post on the grout and sleeve? To fail it the grout would have to be compressed at one side with a gap opening on the other under tension. I haven't seen this happen before, I would check the bearing stresses on the grout and not be too concerned about a bond failure. Applying epoxy to a prepared base should work if you are still concerned.

 

[cvg]

water intrusion and freeze thaw damage to the grout are primary concerns with this type of connection. You need to use non-shrink, non-metallic grout.

 

[kylesito]

non-shrink, non-metallic is the right approx.

I would also recommend upsizing your sleeves a half diamter. This will give some more room for the grout to set up and provide a better connection.



PE, SE
Eastern United States

"If a builder builds a house for someone, and does not construct it properly, and the house which he built falls in and kills its owner, then that builder shall be put to death!"
~Code of Hammurabi

 

[haynewp]

I had assumed non-shrink grout would be used regardless.

 

[JKW05]

Google Quik-Rok and Kwixset. Be careful with the edge distance between the hole and the edge of concrete.

 

[haynewp]

The quik-rok brochure said it was not to be used to anchor balcony railings or other life safety structures.

 

[shobroco]

Most grouts won't withstand freeze-thaw so be carefull of that. I see a lot of railings installed into core-drilled holes into concrete, basically the same as you describe minus the sleeve. I'm not crazy about them, however I think they are better than a sleeve simply because there is one less thing to fail/interface for water penetration, etc.

 

[cliff234]

Thank you everyone for your reponses to my question. The sleeves into which the posts will be installed will be welded to steel beams below the slab, so the sleeves won't pull out. We will be specifying that a bead of weld be installed on the outside of the posts and the inside of the sleeves to provide a keying action, thus preventing the posts from being able to be pulled out. A waterproofing membrane and sealant will be installed to prevent water infiltration around the posts. Thanks again!

 

[ToadJones]

I would consider casting in a pipe sleeve with some studs welded to it or a steel embde plate then attaching to it after ward

 

[dvd]

 

[TLHS]

Four inches really sounds shallow.

Feel free to ignore me, though. I haven't done the math.

 

[grantstructure]

I would put the client's opinion of the type of connection that should be used a distant second to your own in this case. I don't mind embedded handrail bases for, say concrete stairs on grade, but if you're talking a condominium balcony, no way. Provide an embed and weld off to it. They can repair it more easily when the post does corrode, and the post won't fail down in the hole where you can't see the corrosion until it's too late.

 

[racookpe1978]

Many tens of thousands of handrail posts are embedded into sidewalks and balconies only 4 inches thick ... Haven't heard of those failing.

However! Those that I've seen are NOT embedded inside a secondary sleeve. Seems to me that the stress from the handrail needs to be able to "flow" out from the handrail steel through the grout (typically in a 3" dia or 3-1/2" dia drilled hole for a 1-1/4 or 1-1/2 dia handrail "pipe") to the concrete.

A sleeve - with its inside joint to the grout AND an outside joint to the concrete - would be more likely to break out of the balcony concrete than a simple grout-filled hole.

Test it. Pour a 4 inch thick slab of cncrete over a loose fill like sand. Don't be too expensive, you only need it to be 16 to 24 inches wide, long enough to make 10 or 12 holes for your test handrail posts. Try your sleeve, AND a simple hole, with the brands you want to use. If youu want to get fancy, try 3" slab, 4" and 6" - but you only need 4" thick.

Push the top the of the rail at 42" nominal height at 200 pounds force. NOT 200 psi!

See what breaks. The sand won't resist breaking out force of the rail unnecessarily, and reduces expense of doing the test. The wood forms will $30.00 at a hardware store. The concrete? $40.00 Hardest part will be finding a way to measure the 200 lbs sideways force - maybe a bathroom scale?

 

[cliff234]

Thanks again for all of the repsonses.

The secondary sleeve will be welded to the top of a steel beam below the slab. We are not relying on the balcony slab to resist the bending moment at the base of the handrail post. The grout inside the sleeve will be 10,000 psi kwikset. The post will push against the grout. The grout will push against the outer sleeve. The sleeve is welded to a steel beam. The numbers work. We are not relying on bond between the grout and the sleeves for anything. A bead of weld will be installed at the bottom of the posts (4 sides) and on the inside top of the sleeves (4 sides) to provide a keying action to prevent the posts from pulling out.

 

[a2mfk]

Cliff- we have designed handrails and stairs for fabricators for years now, you are doing pretty much how we would do it. You want to transfer that moment directly to the steel structure. Basically all you are doing between the sleeve and the post is providing some bearing material to pass the compressive force into the sleeve, which you have done. I say you are good to go.

But if you do one into concrete with no sleeve, as others have stated you have to give this some more thought. We usually detail some rebar around it and go with a pretty conservative embed depth. Good luck finding an exact calc or example in a text for that one!

 

[dicksewerrat]

Here is a 'grout' from 50 years ago. Heat powdered sulphur till it melts and pour into the space between the post and the sleeve. Did that on a school in the 60's. rules have changed since then.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[spats]

a2mfk,

For calculating a steel post in concrete see the PCI Design Handbook. I have the 5th Edition... it's Section 6.9, pg. 6-27. It's for structural steel haunches, but the same priciples apply to this case.

 

[a2mfk]

spats- I know generally what you are talking about, and have used that method for bearing connections to check for cracking in concrete tie columns and walls underneath the bearing plate. I think we put a piece of rebar between the edge of the concrete and the handrail to cross through the cracking/shear plane to prevent the handrail from spalling off the edge of a slab.

 

[RHTPE]

I do not know the climate where you'll be doing this, but here in my part of the Northeast I would never set a railing post in a sleeve or core-drilled hole.

I can show you pictures of the longer-term results:

1) The "non-shrink" grout cracks the substrate when there is inadequate edge distance.
2) Moisture condensing inside of the pipe accumulates and through various freeze/thaw cycles pushes the post and the grout out of the hole/sleeve.

As they cure, all grouts expand a bit, then shrink. Some shrink to a dimension less than their as-cast dimension. Non-shrink grouts' initial expansion is correlated to its long-term shrinkage, resulting in no dimensional change, which is what allows them to call it "Non-shrinl". I have seen the edges of stairs and the tops of walls split open as a result of poor quality grout,

But of more concern, at least in my area, is the freeze/thaw cycles that can push the grout and post out of the sleeve. I would opt for a cast-in embed and a mechanically-fastened (or welded) post.

Just one man's humble opinion.


Ralph
Structures Consulting
Northeast USA