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

New continous footing overlaps existing isolated footing

New continous footing overlaps existing isolated footing

New continous footing overlaps existing isolated footing

I have a problem regarding the solution for the extension of a 4 story building.
The new columns are very close to the existing columns and the foundations overlap according to the drawing.
The new foundation is a continous footing that is mounted over the existing footing. The reinforcement is not connected with the existing isolated footing.
Can this type of details cause problems in the future for the structure? I've calculated the new foundations as 2 way continous footings and it is a seismic area.
Thank you.


RE: New continous footing overlaps existing isolated footing

Is there any reason that you decided to not connect the existing isolated footings to the new continuous strip footing?

While I am not a structural eng, as they are founding at the same depth I would think that it would be better to connect the two. Dowel some bars in with some hilti resin (the more knowledge structural engs here can advise better on connection details). This would reduce the potential for differential settlement between the two.

A 1m x 1m column is pretty beefy. I imagine you are taking some large loads? Have you looked at settlement? What are ground conditions?

RE: New continous footing overlaps existing isolated footing

Yes there are pretty big loads, about 4000 kN axial load.
The chief engineer suggested this solution and now I started having doubts about the solution. I think it was because the existing structure is already settled on the ground and the new structure has bigger loads.
The ground conditions are good and the building is located between 2 existing buildings (shopping destination). The existing foundations are currently uncovered and the middle part of them is currently demolished.
I could probably check the continous foundation connected with the isolated footings but should I'm afraid that the isolated footing needs reinforcement.
Any help will be appreciated.

RE: New continous footing overlaps existing isolated footing

So no suggestion whatsoever?

RE: New continous footing overlaps existing isolated footing


1) Sizing the addition to the existing footing so that the total soil contact pressure (kN/m2) from the two columns is the same, or slightly lower than the soil contact pressure from the original column on the original footing.

2) Shaping the addition to the existing footing so that the resultant from the two column loads has zero, or near zero eccentricity.

3) Constructing the addition to the existing footing on flowable fill to minimize the importance of subgrade compaction. During excavation for the footing addition take steps to prevent undermining the existing footing.

4) Do not construct what appears to be a 15 cm thick concrete slab (and subgrade) above the footing addition. Stop the proposed slab/subgrade at the edge of the footing addition.

5) Securely connect (dowel) the footing addition to the original footing.

6) Do not use a continuous footing. After the addition, each footing remains isolated. The original footings are isolated... leave them that way.

The above comments are my opinion for a reasonable compromise design. Doubt there is an "ideal" answer.

www.SlideRuleEra.net idea
www.VacuumTubeEra.net r2d2

RE: New continous footing overlaps existing isolated footing

Thank you very much.
I did not connect the continous footing with the isolated one.
I will put polystyrene or something similar between the slab and the continous footing on top of the isolated one.
Thank you again for the advice.

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


White Paper - How ESI is Helping Move New Medical Device Product to Market Quicker & More Cost Effic
Early Supplier Involvement has long been a strategy employed by manufacturers to produce innovative products. Now, it almost seems like a necessity. Because decisions made in the design phase can positively affect product quality and costs, this can help add value to OEM bottom lines. This white paper will discuss many facets of ESI, including why it’s so valuable today, what challenges limit the benefits of ESI, how cost is impacted, and more. Download Now
White Paper - Moving to a Driverless Future
This white paper describes what we see as the best practices to support a sustainable engineering process for autonomous vehicle design. It exposes how to use simulation and testing in common frameworks to enable design exploration, verification and validation for the development of autonomous cars at a system, software and full-vehicle level to drive a mature product development process for automated driving. Download Now
Research Report - How Engineers are Using Remote Access
Remote access enables engineers to work from anywhere provided they have an internet connection. We surveyed our audience of engineers, designers and product managers to learn how they use remote access within their organizations. We wanted to know which industries have adopted remote access, which software they are using, and what features matter most. 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