×
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

Building Concrete Columns in the Soil

Building Concrete Columns in the Soil

Building Concrete Columns in the Soil

(OP)
Will a concrete column supported by soil buckle? Can we say that the effective length factor K=0 for this condition and therefore makes the critical buckling load Pcr undefined?

RE: Building Concrete Columns in the Soil

Are you refering to a column that is confined on all sides by the soil? or is this an element that only has soil on one side? One way to explore this is by doing a P-delta analysis, modeling your soil as a spring at regular intervals. I would think that buckling would not control in most cases, but a very slender element in poor soil may be a different story.

RE: Building Concrete Columns in the Soil

I would limit the capcity similar to that of a reinforced concrete drilled shaft.

RE: Building Concrete Columns in the Soil

No, you can't use K=0. The soil, unless it's compacted more than you would want to adjacent to a column, will not provide lateral bracing. Use an effective length of base to top.
Once buckling commences, the forces are pretty large. A small lateral movement is all it takes to get it started. To activate even the active pressures, takes more movement than it would take to start buckling.

RE: Building Concrete Columns in the Soil

It sounds more like a foundation pier or pile. The 2006 IBC section 1808.2.9.1 states: "Any soil other than fluid soil shall be deemed to afford sufficient lateral support to the pier or pile to prevent buckling . . ."

RE: Building Concrete Columns in the Soil

There was just one case in memory when the soil was deemed inadequate to provide lateral support to the pile. It wasn't liquid, but it was extremely soft. Ordinarily, piles are considered laterally braced by the soil but it is a matter of engineering judgment.

BA

RE: Building Concrete Columns in the Soil

Maybe I'm misinterpreting this, but from the question, I was thinking it was a column on a spread footing, and backfilled around it. For a cast in place concrete pier, I would expect the loads to be low compared to the concrete strength and bucking and lateral support is not an issue, hence the code direction.
But sometimes we have to support a structure with columns below grade. This happens when there's a building or a portion of a building constructed on a deep excavation. Before the excavation is filled, we have columns constructed on footings and the backfill installed around them.

RE: Building Concrete Columns in the Soil

The North Elevation and the top half of the South Elevation act pretty much as a shearwall. The bottom half of the South Elevation needs to be assessed as a kind of frame.

Continuous bond beams would seem to be a good idea above and below each opening and at floor level.

BA

RE: Building Concrete Columns in the Soil

Wrong thread, BA. Don't you just hate it when that happens?

RE: Building Concrete Columns in the Soil

Maybe the OP was wrong?

RE: Building Concrete Columns in the Soil

Yes, wrong thread. Please ignore my comment.

BA

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