Hand Rail Post Embedment Depth

[karinmk]

I've been doing stair & railing calcs lately (yeehaw) & need to know how to calculate the embedment depth required for the steel posts in concrete slabs. Often it's a thin concrete floor slab, 4" or so. I've looked at PCI Design Handbook EQ 6.9.1, but I don't know if this is applicable to an unreinforced, or just S&T slab. What would be used for the effective width of the compression block, b? Is there a minimum cover between the base of the tube & the bottom of the slab? The forces are so low, but in submitting calcs, need to show something?

Any advice?

 

[hokie66]

Handrails are not usually embedded, but rather bolted to the concrete, or sometimes welded to embedments. A 4" slab would be too thin for a handrail connection.

 

[Ron]

Nope...4" embedment is common. Use a triangular stress distribution from surface down. Check for compression failure (won't happen with the low loadings), but will satisfy reviewing authority.

Most common failure in handrails (outside moment at welded connection) is localized crushing or excess moment of aluminum post tubes at top of embedment. Steel is not usually an issue, since most stair and rail fabricators use 50 ksi material.

 

[par060]

I think I would look to bolt to the top of the slab rather than embed. 4" isn't much embedment amd the lever arm would be kinda long...I can see some kids ruining the slab

 

[karinmk]

Thanks for the imput. This particualar rail is near grade, so I'm letting it go, but hope to come up with a better calculation to support in the future.

 

[RMPE]

suggest a turned down edge or pocket for post with a U bar around post into slab and adequate cover...concrete usually fails by cracking edge off slab caused by corrosion of post. Use caulk around post base to keep away water and salts.....never happens!