×
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

Circular Concrete Tanks

Circular Concrete Tanks

Circular Concrete Tanks

(OP)
Are the charts in PCA's "Design of Circular Concrete Tanks Without Prestressing" valid for negative loading?  That is, can you check the empty condition with soil (and liquid, if applicable) on the exterior by simply using a negative load?  Is it as easy as a matter of sign convention?  The book mentions the need to check all load conditions, but doesn't directly say that the charts work that way--unless, of course, I missed it.  Thanks in advance.

RE: Circular Concrete Tanks

External pressure on a cylinder loads the shell in compression.  I assume the charts in the book you reference are giving the reinforcing requirements, and those wouldn't be applicable for compressive loading.  Those charts may also be based on crack control which wouldn't be an issue in compression.

Thin shells loaded externally will buckle well before any yielding takes place.  I doubt this is the case with reinforced concrete walls with uniform loading, but it shouldn't be too hard to check.  See Roark's formulas for stress and strain, for example, which includes eleastic buckling of short cylinders.  I'm not sure what thickness or stiffness values you'd use for RC, but I wouldn't think it would be hard to show adequacy.  Uneven loading around the tank might be more of a problem.

By way of comparison, you might note that the wire-wound concrete tanks are loaded externally by the wire, but still use thinner walls than reinforced concrete normally does.

If you had any significant water pressure on the underside of the floor, you could have problems from uplift.

RE: Circular Concrete Tanks

(OP)
Never mind. . . .  I read on, and found my answer in the design examples.

RE: Circular Concrete Tanks

And was it a yes or a no???

RE: Circular Concrete Tanks

(OP)
Oops, sorry.  The answer is yes.  Ring tensions become ring compressions, and moments are obviously reversed.

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