Handrail/Guardrail Embedment
Handrail/Guardrail Embedment
(OP)
I've searched the several threads on this topic but haven't came to a clear understanding of the design of the embedment of handrail/guardrail in concrete. I realize that there is some debate as to whether core drilling posts in concrete slabs or retaining walls is the ideal installation over other alternatives (base plates, cast-in-place sleeves such as EZ Sleeve, etc.), but in my experience embedment of steel, stainless, or aluminum (with coatings) posts in concrete with non-shrink grout is commonplace. Can someone clarify the procedure to calculate the required embedment depth? Or even point me to some resources? Thanks!






RE: Handrail/Guardrail Embedment
DaveAtkins
RE: Handrail/Guardrail Embedment
RE: Handrail/Guardrail Embedment
http:/
RE: Handrail/Guardrail Embedment
Anecdotal - I have noticed several failures when the handrails are placed in concrete sidewalks or slabs very close to the edge, failed via a shear crack where the edge of the concrete spalled completely off. If its a structural slab and you can call out for an "insurance" rebar at that edge, its always nice :)
RE: Handrail/Guardrail Embedment
RE: Handrail/Guardrail Embedment
DaveAtkins
RE: Handrail/Guardrail Embedment
If I'm stuck with using a core, I use two opposing, rectangular bearing stress blocks, one from the top to the halfway point, the other from the halfway point to the bottom. This makes my moment arm half the depth of the core. It is tempting to use triangular blocks and make the moment arm two thirds of the depth, but that assumes unyielding pipe and is unconsevative.
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Handrail/Guardrail Embedment
RE: Handrail/Guardrail Embedment
RE: Handrail/Guardrail Embedment
RE: Handrail/Guardrail Embedment
The sketch shows resistance to the moment, but not the lateral load.
paddingtongreen,
I think a triangular bearing assumption is more realistic, and conservative.
DaveAtkins
RE: Handrail/Guardrail Embedment
RE: Handrail/Guardrail Embedment
RE: Handrail/Guardrail Embedment
RE: Handrail/Guardrail Embedment
RE: Handrail/Guardrail Embedment
Same for lateral force, though it can be argued that a smaller stress block applies for the shear area. In actuality, the conservative approach would be to consider single shear through the concrete at the centerline of the post, extending E/3 downward, and to the outside edge of the concrete. Interior doesn't matter since the area of concrete in shear is way too large to be of consequence.
RE: Handrail/Guardrail Embedment
But when I build handrails into a slab or existing concrete sidewalk, I'm limited since the "base" is already solid.
What " works" - but I emphasize! not analyzed - is to core drill the sidewalk all the way through the concrete to dirt. If a slab, go down no more than 6 inches - since the core drill jams out any deeper. I've had no problems with holes only 4 inches deep, but prefer to go further if the sidewalk allows it.
On porches or wlakways in the open air, sometimes I can only go 3 inches deep before I bore through. If so, then I have to fill/plug/block off the bottom of the hole so the concrete doesn't just slide through the opening.
Plan on a 1-1/4 dia pipe (or equal) as the vertical, and get a 3.5 inch core drill. 4 dia if you can find one. The bigger the hole the easier it is to force the grout/concrete around the pipe without making a mess. Build and install the handrail pipe so it goes 5+ inches deeper than the surface, but doesn't hit any dirt.
Pour/insert/tamp the "expanding" grout/concrete around the post so you slightly over-fill the hole to force water runoff.
Keep the post supported overnight. Test the top of the handrail at 200 lbf the next day.
Note again: This is not a designed solution, but a construction "solution" report.
RE: Handrail/Guardrail Embedment
RE: Handrail/Guardrail Embedment
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Handrail/Guardrail Embedment
RE: Handrail/Guardrail Embedment
You should be using a 1 1/2 standard pipe not 1 1/4"
A 200# concentrated load at 42" above grade requires a section modulus of at least .263 if you are using a code that permits a 1/3 stress increase for guardrails.
While fence pipe can be obtained in grade 50 steel most handrails are made with A53 steel which is 35 KSI with an allowable bending stress of 24 KSI.
A Pipe 1 1/4 STD has a section modulus of only .235.