×
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

SPLIT HAIRPIN???

SPLIT HAIRPIN???

SPLIT HAIRPIN???

(OP)
PEMB – (Pre-Engineered Metal Building)

12K Horizontal Thrust.

The concrete sub-contractor installed a SPLIT hairpin because they RAN out of rebar!!! I told the general contractor site supervisor that the split hairpin is useless.

Not only THAT – NOW the concrete slab is poured which means I have no access to either the front or sides of the concrete pier in order to post-install anchors for a possible fix for this problem.

THOUGHT #1

HOW do I fix this? “Rip it out and start over!” is my first thought.

Continuous tie-rod(s) from back wall to front wall? We’d have to remove a lot of concrete slab. Too bad!

THOUGHT #2

The foundation is 4’ frost wall.

My thought is: 12K horizontal thrust on top of a concrete pier with (4) #6 vertical rebar doweled to a concrete footing, with four feet vertical of unending horizontal soil behind a 4’ high continuous concrete foundation wall. I realize that I have much to understand regarding soil mechanics and engineering, but, is 12K REALLY going to move this foundation?

Akin to differing opinions from a past thread regarding uplift on PEMB foundations, particularly a small PEMB in Florida, reportedly, with no regard for uplift resistance, is 12K REALLY going to move this foundation?

However, we DO design for the worse case. Rip it out! Start over!

Thoughts? Thank you!

RE: SPLIT HAIRPIN???

Can you just remove the area that the hairpin was going into? or sawn joint to sawn joint and repair?

I would say that they need to install it as it should be, hairpins are a little black magic in my eyes but less creepy than nothing

Analyze your wall as a cantilever, can it handle 12k thrust? maybe... probably not

RE: SPLIT HAIRPIN???

One way to check it is to see if the overturning affects the bearing pressure of the footing. I would include the effect of an active soil pressure (no passive) to counterbalance the thrust a little, and see if sliding and overturning on the footing is OK. If that doesnt work, you can check it with passive pressure, but you need to mobilize the wall a bit to achieve that.

RE: SPLIT HAIRPIN???

(OP)
Eric… Your first suggestion is a practical option. Thank you!

The pier is 15” perp x 30” parallel to adjacent wall. A cantilevered concrete beam with (6) #6 rebar works great! But, is the soil and adjacent concrete wall an acceptable support for the reaction?

With 2,000 PSF axial soil bearing capacity, this appears MORE than sufficient.

With 2,000 PSF axial capacity, how do I determine horizontal capacity? This is where I lack with soil engineering.

structSU10… I will check into that. Thank you!

RE: SPLIT HAIRPIN???

2,000 psf is darn weak stuff both vertically and horizontally. You may have more for each. Heavy compaction on earth outside the wall may well suffice, but if it is frost susceptible and a cold climate (much of USA), in time that compaction of beefing up or some other method of passive resistance may well be less than the option of demolition and tying into existing re bars, etc. Replacing that frost susceptible soil with clean sand and gravel, compacted is not affected by frost. 4 ft width would help a lot. Look at an a triangular equivalent density pressure distribution of roughly 400 pcf density, or more.

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