×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Guardrail Pocket Failures

Guardrail Pocket Failures

Guardrail Pocket Failures

(OP)
I've never been a big fan of the Guardrail embedment detail for exterior applications. This is in a normal climate (some freeze/thaw, but not excessive). It is hot-dipped galvanized railing that is about 5 or 6 years old, embedded 5" into concrete below and grouted. I don't have the specs on what grout was used, but clearly this isn't working...anyone had success on a retrofit without replacement?

I'm thinking about having them chip out the grout, clean the steel and replace with an epoxy grout that isn't as permeable, then put a rain cover type piece over that to shed water...I don't like that much either, but it could be a temporary bandaid



RE: Guardrail Pocket Failures

(OP)
Also, I think a root cause of issue is that the grout pockets hold water as they aren't flush with the concrete above, forcing water to constantly be in contact at the connection...but I still don't like this detail!

RE: Guardrail Pocket Failures

Is the bottom capped so that water can be trapped? there should be provision in the detail to prevent a void space there should also be a hole at the bottom to drain water... Even a 1/4" hole can be used to flow in flowable grout. I've heard that water expands with a force of 2000 psi...

Ron: a classic example of your post embedment type of installation.

Dik

RE: Guardrail Pocket Failures

(OP)
The bottom does not appear to be capped. Appears open, see below from shop drawing...I don't have original design documents showing designer's intent, just shops.

RE: Guardrail Pocket Failures

Do you think it was freezing water expansion or corrosion jacking that caused it?

RE: Guardrail Pocket Failures

dik, there is no limit to how high the pressure can get when water freezes. It depends on the containment and how it freezes. The worst case is when water freezes in a pipe progressively from one end to the other, in which case the water keeps getting squeezed into a smaller and smaller volume. The first part of the pipe to freeze will see very little stress and will not be participating in expanding as the water freezes.

A pipe that freezes from top to bottom across its diameter will radially expand uniformly along its length. In this case you can calculate the expansion pressure due to freezing.

RE: Guardrail Pocket Failures

dik....yep....seen thousands of them. Often problematic but certainly more load resistant (until it corrodes and fails!) than typical baseplate attachment.

RE: Guardrail Pocket Failures

(OP)
I do think it was freezing water/corrosion jacking that caused it, but more freeze thaw. I hope the pictures are helpful too as we all consider this detail moving forward.

Ron, have you seen any good ways to do this or retrofit? Again, I'm thinking they chip out the grout, go back with a less porous grout and then put some sort of rain cover to try to keep the water from getting in/around the rail. It would only be a bandaid though

RE: Guardrail Pocket Failures

CompositePro... thanks

Dik

RE: Guardrail Pocket Failures

I would guess that that the posts are beyond safe use.
Leaving them below grade created a bad situation.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Guardrail Pocket Failures

I've run into this a few times on retaining walls and on guards at slab edges.

A better practice is to use a flush plate with embeds. You can weld to it later.

A side mounted plate for retaining walls is also good.

RE: Guardrail Pocket Failures

Guastavino....even if you could chip out and replace the grout, you have section loss from corrosion in the posts. These should be fully replaced or sleeved and welded at the bottom and extend several inches above the grout line. After sleeving, corrosion protection will have to be done, but will likely not be as good as the original hot-dipped galvanizing.

RE: Guardrail Pocket Failures

(OP)
Does anyone have a good summary of the best locations for weep holes with guardrails? I would think that condensation could get inside the rail on hot/cold cycles, drip to the bottom of the pipe, likely not dry-up, and then freeze thaw from inside the pipe. Is that crazy talk?

RE: Guardrail Pocket Failures

(OP)
I'm also thinking that a good way to make this detail work (the embedded post detail) would be to leave a 1/4" hole at the base of the rail, fill the base full with spray foam insulation (such as Great Stuff). That would prevent water from getting in. Then, either make the grout with a slight dome shape to shed water, or make the grout flush and put sealant around the pipe edge. I'm trying to think what problems that could cause...

That's a decent amount of extra work, but those guardrails in the photos are only about 6-7 years old.

RE: Guardrail Pocket Failures

If you seal weld the post top and bottom, it will prevent moisture inside....mostly.

RE: Guardrail Pocket Failures

Quote (Gustavino)

Does anyone have a good summary of the best locations for weep holes with guardrails

You can introduce a small 1/4" dia hole about 2" above the surface and can use this hole to fill the embedded part of the pipe with a flowable or non shrink grout. This will prevent water from freezing in the lower part and expanding. Have done that numerous times... same with exterior HSS columns... even if there is no chance for water to get in.

Dik

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close