×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

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!

*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

Repair recommendations for building with shallow footings experiencing subsidence

Repair recommendations for building with shallow footings experiencing subsidence

Repair recommendations for building with shallow footings experiencing subsidence

(OP)
I've been contacted to provide some repair recommendations for a building which has experienced shallow footing subsidence caused by an adjacent sub-grade parking structure excavation. The adjacent lot was excavated and the excavation walls were temporarily supported using anchors and reinforced shotcrete in several stages (I think 5). The tenants noticed several symptoms of subsidence and engaged some engineering service providers who engaged a geomatics firm to quantify the lateral and vertical displacement of several reference data. Surveys were performed every few days, and now the adjacent building is completed and lateral and vertical displacement is no longer increasing. So, it's time to fix the tenant's building.

The building is founded on shallow concrete footings with a series of structural-steel portal frames. There's not much to this building. Four gridlines one way and two the other. The displacement does not strain the strucutral steel or connections excessively.

The photographs of the building following subsidence show lots of cracks in the drywall, doors that are unable to function properly, and several large cracks in a concrete SOG floor.

I have two school's of thought on this repair.

1) Really Mike-Holmes it, and, "Make it right!" Recommend some screw piles to return the footings back to their original vertical location, repair/replace sections of the SOG floor (maybe some mud-jacking) and fix the drywall/doors. Some challenges with this. The piles would need to be installed from the interior (I have some experience with this in tight headroom locations), and there's no outside wall access (the new building is inches away).
2) Let sleeping dogs lie, and largely leave it alone. Repair/replace the slab, and fix the doors/drywall.

What am I seeking? Some advice from an engineer who's done this a few times. What's typically done? Any advice would be greatly appreciated.

RE: Repair recommendations for building with shallow footings experiencing subsidence

I haven't had quite your situation - I haven't done much dense commercial and everything outside of the CBD where I am has to be at least several feet apart. That, and nobody ever has that much data.

Even so, I usually recommend #2. What is there to gain by doing #1? You said yourself that the frame isn't being stressed excessively (I'm guessing you modeled it - computer or by hand - with a forced displacement to verify?) and the issues are almost entirely serviceability related. To do #1, the cost is likely going to be hundreds of thousands of dollars more than #2 and you'll have the same functionality when you're done.

The new building owner next door may be footing the bill, but you can bet they'll be picking through the plans and the costs with their own engineer to make sure you're not doing anything excessive.

RE: Repair recommendations for building with shallow footings experiencing subsidence

Kinda depends on the level of quality of the structure. Removing and reporting the slab will not level any floors or walls above.

Mike McCann, PE, SE (WA, HI)


RE: Repair recommendations for building with shallow footings experiencing subsidence

Use helical or hydraulic pushed pin piles and bring the foundation back to level. Fix the slab either with epoxy injection or replacement.

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! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

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