×
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

Subgrade modulus of Reinforced concrete

Subgrade modulus of Reinforced concrete

Subgrade modulus of Reinforced concrete

(OP)
HI ,

presently i am modelling the base plate and analyzing the behaviour of base plate under axial load and moment.
Can anyone let me know the subgrade modulus of reinforced conrete , which i have to use for finite element analysis

RE: Subgrade modulus of Reinforced concrete

Subgrade modulus is a term used to describe the properties of the subgrade. It is not used to describe reinforced concrete.

BA

RE: Subgrade modulus of Reinforced concrete

(OP)
I agree but i modeled the base plate as a plate element where the base is resting on the concrete, So what kind of support i would use can any one let me know.

RE: Subgrade modulus of Reinforced concrete

The modulus of elasticity of concrete is known approximately as a function of its strength.

BA

RE: Subgrade modulus of Reinforced concrete

That would be one of the drawbacks of using finite element analysis.

You could assume uniform loading under the base plate. Or linearly varying loading if there is a net moment.
For a small plate on larger concrete slab, you could assume that the mid-surface of the concrete was fixed, and treat the concrete above that as elastic in the vertical direction only.
You could include the concrete as part of the finite element problem also, which introduces other complications.
In a lot of cases, for the base plate design, assuming uniform loading on the bottom will be conservative.

Note that treating a subgrade as an elastic foundation (elastic vertically) can give considerably different results from treating it as an elastic solid. So it's an approach that is useful, but not necessarily an ideal solution, either.

If you have to use very crude approximations to get a solution to a problem, you should consider using very crude approximations that also simplify the problem. So perhaps uniform bearing and a yield-line analysis would be in order.

RE: Subgrade modulus of Reinforced concrete

A while back, someone posted a video here that was an engineer from Utah summarizing a very well thought out FEM method that he used to assess anchor bolt and base plate stresses at braced connections. I remember there being information in the presentation to do with the concrete stiffness and I remember being surprised by it (not just concrete E). Hopefully someone will remember that presentation and post a link to it. I'd like to check it out again myself.

Like JStephen, for a real design I prefer a simplified non-FEM approach. Even the information in the video that I mentioned seemed a little questionable to me, despite it being very well thought out.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Subgrade modulus of Reinforced concrete

If the column has axial load and moment, then the foundation will settle and rotate. If the foundation is a footing or pile, its rotation will be resisted by soil and that is where the subgrade modulus comes into play, not at the underside of base plate.

BA

RE: Subgrade modulus of Reinforced concrete

That is the very presentation iv63. ThankS so much.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

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