Handrail Post Embedment Edge Of Slab

[TomWaggoner]

Working with a new client who has been installing handrail posts with a 1 1/2" edge distance for years. As the new engineer they need me to create calculations for their shop drawings. I can't get the calculation to work for a 6" deep embedment into the concrete. They typically have the following criteria: Fc'=2500psi (sidewalks) Post Spacing=5'-3"
I resolved the moment at the base of the post using a 4" T-C couple in the embedment. That seems as a reasonable pressure resolution of forces. I end up with 2.7k unfactored. Adding in the 1.6 factor to 4.4k. If I do just a straight shear calculation in a shear plane and just forget about appendix D for a sec,. I only get around 1000#,. I got around 385# using appedix D if I don't avoid D.3.3.6,. how have any of you got this to work? What am I missing? any and all help is much appreciated. Thanks!

 

[TDIengineer]

I usually check the post working all in bearing on opposing faces. Consider the upper half of the pipe and a blowout cone to the side face. I would use oldschool CBC anchorage to concrete values where you look at your project Ap to determine your allowable pull-out...

If it has to be to current code you won't ever get it to work with Appendix D for just 1 1/2".

Can you use a #3 hairpin and resolve the force couple by developing the rebar? That is your only hope, OB1, with that tight of edge.

 

[connectegr]

Without a curb plate or other edge reinforcement, you will not get 1 1/2" to work. In most cases 5'+ post spacings will also not work.

http://www.FerrellEngineering.com

Providing fabrication and erection efficient structural design of connections. Consulting services for structural welding and bolting.

 

[msquared48]

With that edge distance, If the slab is yet to be poured, I would look at the use of two #3 or $4 hairpins cast into the sidewalk at the handrail post locations, one top and one bottom, to take the tension forces generated at the top and bottom.

If the slab is existing, you have my sympathies... But could you possibly core drill through the sidewalk and underpin underneath with a new footing for the handrail, not depending at all on the sidewalk?



Mike McCann
MMC Engineering

 

[TomWaggoner]

yeah msquared48,. the slab is existing,. they have a couple conditions one with 2500psi concrete sidewalk and a 4000psi wall that is 6" wide,. Feel like I am working myself out of a new client. But hey the calculations are calculations,. and to top it all off the previous engineer they used,. that unfortunately died,. has a calculation for the post which never addressed edge distances,. client asked why we can't just use the old calculation,. explaining to contractors is always fun,. thanks for the input guys!

 

[connectegr]

Calculations will not work. But one option is to build and load test a sample. Often an actual load test will far exceed our theoretical design requirements.

http://www.FerrellEngineering.com

Providing fabrication and erection efficient structural design of connections. Consulting services for structural welding and bolting.