×
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

Post Hole Foundations

Post Hole Foundations

Post Hole Foundations

(OP)
Hi all,

I'm wondering if any one has information on post hole footings, i.e. how they work (cantilever action?) and how to design them (reinforcement, overturning moment).

Any help is appreciated.

Thanks.

RE: Post Hole Foundations

What are you trying to build? A fencepost, equipment support, house footing and utility pole all have slightly different constraints and things to look out for. Reinforcement is also a question of how you've attached your post. Embedded fenceposts may not need reinforcement depending on how you've detailed them, for instance, but a concrete footing that you've bolted a post to the top of certainly will.

Your start point is likely going to be the IBC post foundation formulas, if you're looking at small scale items that aren't significantly deflection sensitive.

RE: Post Hole Foundations

The proper term is "Pole Footing". You will find what you need in the IBC as mentioned, but also the AITC and Google. Lots of information available. Depending on the nature of what you are doing, you may need at least a PE design and stamp too.

Mike McCann, PE, SE (WA)


RE: Post Hole Foundations

Check out the Post-Frame Building Design Manual, also ANSI/ASAE EP486.1

RE: Post Hole Foundations

Assuming these are analogous to "post footings" typically used in Australia where steel posts are cast into bored piers to support residential construction (i.e. clad frame buildings elevated above ground level) I will share what I have found from my research:
1) cantilever action can be relied on for posts up to 900mm in height (limitation given in the timber framing code AS1684.2)
2) for heights above 900mm cross bracing sets are required to provide racking resistance
3) footing depth is determined by considering two factors. First is how much lateral/uplift capacity is required to resist wind loads. Second is how deep the footing needs to be to resist predicted ground movement in reactive sites prone to shrinking/swelling soils.

For lateral resistance, I usually just design as normal piers by estimating the un-drained shear strength of the soil based on the classification given in the soil report(20-30kpa usually - but I would prefer a geotech to make a recommendation rather than having to estimate values for each job). I have not seen the IBC reference before, thanks TLSH.

Jake

RE: Post Hole Foundations

But little in Australia is written against frost depths, right?

Even the local building codes here (NW GA, US) get pretty restrictive on "post holes" for outdoor decks. You need to define your problem (your application and your country and state/province) much, much better.

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