Contact US

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.

Students Click Here

Calculating Outward Busting forces for cranked rebar in circular columns

Calculating Outward Busting forces for cranked rebar in circular columns

Calculating Outward Busting forces for cranked rebar in circular columns

How do I calculate outward busting forces in a circular concrete pile at positions of cracked longitudinal rebars. This column is 800mm dia with 15No dia 32mm bars to enable splicing. The pile is 23m long. The rebar has 2 spices. Links are a spiral dia 16mm bars at 250mm pitch. Because there are so many bars (15No) this makes the tie bar angle so wide that trying to resolve the forces seems to require quite some substantial additional links to counter the outward busting force. Is it allowed to just resolve the forces in this way and provide as much tie reinforcement as is necessary? Is it possible for someone to help me with an example of how to calculate the busting force or guide me in the right direction? Thank you

RE: Calculating Outward Busting forces for cranked rebar in circular columns

Why crank the bars? I agree that restraining the horizontal force at a crank of a large bar is problematic unless there is a horizontal concrete element at that point. But it you just lap the bars around the perimeter without cranking, I think the problem is much less.

RE: Calculating Outward Busting forces for cranked rebar in circular columns

Force in bar X Crank H/V = Outward Bar Force.

Add up the contribution of all the bars to hoop stress in the ties and you'll have the demand on the ties.

I think it's allowed to reinforce for crank busting forces in this way but you'll have to give some thought to how you'll integrate your concentrated local ties with the spirals above and below the cranks. Hokie's method sounds much simpler if it will work for you.

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: Calculating Outward Busting forces for cranked rebar in circular columns

Thank you so much for the tips.
Hokie66, the reason for cranking the bars has been requested by the contractor. The original cage had full length bars but the contractor prefers to do the cage in segments using casings a relatively smaller crane for lifting the prefabricated cage. Cranking the large diameter bars rather than simple laps side by side appears to give more spacing between bars for concrete to flow. My understanding is that for large dia bars the gap between the bars should be at least 100mm for concrete to flow?.
KootK ,I have applied the formula, does give some reasonable ammount of rebar area for ties. Should be able to continue the spiral links over if I use smaller diameters for the ties. Much appreciated.

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! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

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