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!

*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.

Jobs

PT Slab on Ground on piles - Detailing Query / General Input

PT Slab on Ground on piles - Detailing Query / General Input

(OP)
Hi guys,

Currently working on a portal frame factory founding in very poor soil conditions, supporting heavy stacking loads. The site requires approximately 2.3m of fill over soft compressible clays, and the soils report states that due to long term settlements in the clay layers the floor slab must be designed as suspended on piles.

The client wants to investigate using a PT suspended slab supported on screw piles or driven timber piles. Our initial concept was to use a one way slab and band beam arrangement, with the beams being at equal centres to the portal frames (7500mm). We have run some numbers and come up with a preliminary design, but my main concern is detailing the slab to limit soil restraint from the grade beams as much as possible and give the slab a chance to elastically shorten when stressed.

Does anybody have any rules of thumb or references for the maximum gradient between underside of band beams (or edge thickenings) and the slab to prevent restraint?

Alternatively, all I can think of is using some sort of compressible material around the band beam edges. Haven't given it too much consideration yet, but if anyone has done this or heard of something similar any input would be much appreciated.

We will also be providing a flat slab arrangement with a tighter pile grid for a comparison with the client, which obviously wont have the same soil restraint issues.

Thanks in advance


RE: PT Slab on Ground on piles - Detailing Query / General Input

All the industrial PT slab on ground examples I have seen are flat slab construction with no beams.

One big issue is all the detailed excavation required to form the beams.

EDIT: Refer PTIA seminar notes:

http://www.ptia.org.au/Documents/Heavy%20Duty%20In...

RE: PT Slab on Ground on piles - Detailing Query / General Input

Some people have suggested about 1 in 6 but I do not agree. Any slope is going to cause problems. You are also going to get significant restraint from the piles and the subgrade on the flat soffits.

So cracking is inevitable. .6% reinforcement + PT is about the only solution to control the crack width.

RE: PT Slab on Ground on piles - Detailing Query / General Input

For calculating restraint from the subgrade on a flat soffit you can use a friction coefficient of 0.5, which assumes a layer of polythene over a sand blinding layer.

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


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