Flagpole calculation for guardrail 1

[shacked]

A prospective client called me because the City issued them a stop work order on a ground level guardrail that was not permitted.

This is a brick deck on grade at their front yard and the edge of the deck at the sidewalk is approximately 4ft above the sidewalk.

The owners have already placed the posts in concrete (12" dia x 18" deep piers) all around the deck.

My issue is that when using the IBC flagpole formula and the allowable lateral soil pressure (100psf) as prescribed in the code the piers require 3ft embedment. I don't think that the calculation is intended for such a small pier footing or loads. 200lb point load placed at the top of the guardrail.

I have searched on this site and have not found anything that I could use in order to justify the posts that have already been cemented in place.

Does anyone have any ideas or thoughts about this?

THanks

 

[Ron]

Load test them. Simply test, doesn't take long to do and a lot less expensive than tearing down and rebuilding.

 

[shacked]

Ron, thanks I never thought about that. After reading through section 1708 of the CBC (California) for in situ load tests it looks like I would have to specify the load test procedure. Since this would be paid for by my client and in order to keep costs to a minimum do you think that it would be acceptable to simply attach a come-along to a strap placed around the top of the post with an inline tension meter/scale and attach the other end of the come-along to a large tree or car. Then tension the come-along until 200lb is reached and then maintain that tension for 10 minutes?

Obviously have a deputy inspector there to monitor the tests and document the results.

Or are there actual testing agencies that have to perform the test? In this case I am sure that their fee would be a lot.

Thanks

 

[Ron]

shacked...You can do that, but remember that the 200 lb lateral load is for both pushing out and pulling in. You'll only be testing one condition...your inspector or code official might require both directions.

We use a hydraulic jack with a load cell attached in line.

 

[oldestguy]

If no tree for an anchor, how about installing an eye bolt in the concrete or similar in pavement (might have to be deep), then run chain or cable up and over a "chair" to get a horizontal pull on the post via the portable tension scale.

 

[Bobby46]

Check out Precast Concrete Connections with Embedded Steel Members by Marcakis and Mitchell. It's from a PCI Journal July-August 1980

I can't find my copy online, but here is his thesis

http://digitool.library.mcgill.ca/R/?func=dbin-jump-full&object_id=54736&local_base=GEN01-MCG02

 

[DaveAtkins]

You can double the 100 psf per foot lateral bearing pressure, as long as you are comfortable with 1/2" movement at grade (IBC 1806.3.4).

DaveAtkins

 

[Toby43]

Ron,

Interesting load test setup. What measures do you take to "catch" the balustrading if it fails during testing? or does the load shutoff at a prescribed displacement?

Regards
Toby

 

[Ron]

Failures are usually ductile, so plenty of warning.

 

[EireChch]

That would be a nice view for the day...

 

[Ron]

EireChch....Jacksonville, Florida along the St. Johns River. Taken from 38 story condominium building on the south bank of the river, looking northeast toward the stadium where the Jacksonville Jaguars (American Football) play (stadium is in background).

Agree...not a bad view! When we were doing structural testing on the windows, dolphins were playing in the river below.