×
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

Post-Installed Anchors - When to assume cracked vs. uncracked concrete

Post-Installed Anchors - When to assume cracked vs. uncracked concrete

Post-Installed Anchors - When to assume cracked vs. uncracked concrete

(OP)
Hi all,

Im reviewing a contractor's shop drawings for handrails. Structure is an existing 18 story hotel in Waikiki and all guardrails on the room balconies are being replaced. The contractor is showing use of proprietary expansion anchors that are not ICC approved for use in uncracked concrete. The contractor's handrail fabricator's engineer claims that the handrail baseplate anchorage locations on the existing concrete balcony decks are not located in tension zones so uncracked concrete assumption is ok. Our firm's policy is to always assumed cracked condition for this type of application, especially on existing structures.

Would you guys approve this anchor?

Thanks.

RE: Post-Installed Anchors - When to assume cracked vs. uncracked concrete

I don't know.  If you are sticking to IBC 2006 which requires code approved anchors, I probably wouldn't.  I never assume uncracked concrete, ever.  It's just a bad idea.

Additionally, if you are the EOR, you should be telling him to assume cracked or not.  I don't think the comment, "it's not in a tension zone" is sufficient.

RE: Post-Installed Anchors - When to assume cracked vs. uncracked concrete

The existing balcony deck is probably a cantilever and ask him to prove that the top face of the deck is not in tension.

RE: Post-Installed Anchors - When to assume cracked vs. uncracked concrete

If it is not in tension now, it will be after the installation of expansion anchors.

RE: Post-Installed Anchors - When to assume cracked vs. uncracked concrete

If's its in the top surface of a cantilevered slab, then I would call it the tension zone and require the cracked concrete calculations.  

I agree with slickdeals. Explain to him that the top surface of a cantilever is almost the definition of a tension zone.  

If he disagrees, then ask him to explain to you the code basis for referring to it as something else.   

RE: Post-Installed Anchors - When to assume cracked vs. uncracked concrete

Definitely, assume the cracked condition in the top of a cantilevered balcony.  It seems difficult to argue otherwise.  

If you require someone to oversee the work in Waikiki, I would be pleased to proffer a proposal.

BA

RE: Post-Installed Anchors - When to assume cracked vs. uncracked concrete

Everyone,

I have been to hotels and condos that had balconies with columns or walls in the corners of the balcony - not a cantilever. So perhaps in this case, it is not a cantilever.

I don't have a problem assuming uncracked when that can be CLEARLY established.  However, even if this balcony is supported in the corners, there could be slight fixity near the supports, that is, negative moments and cracks.  In the end, some anchors may be in cracked sections so I agree that cracked sections should be assumed.

RE: Post-Installed Anchors - When to assume cracked vs. uncracked concrete

Don't forget that many cracks in concrete structures are due to restrained shrinkage rather than flexure.  If it is a long building, some cracking across the short dimension is almost inevitable.

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