Ask HiltiAskLearnArticles
Ask Hilti

Why is breakout capacity so sensitive to direction?

Posted by Jonathan Stewartover 6 years ago
Why is breakout capacity so sensitive to direction?

I am designing anchorage for a column, and came across an odd behavior in the Breakout failure capacity calculation in PROFIS Anchor. I simplified the problem, and saw the same behavior.

I modeled a 12" square 1/2" baseplate, held by 4 anchors in a 10" square pattern to 2500 psi cracked concrete. If I apply a constant 5 kip-in moment, but rotate the direction of the applied moment, the capacity (and utilization) suddenly jumps from 22% to 42% when the contact neutral axis crosses an anchor position. What causes this discontinuity in capacity/utilization? The load on the anchor group is continuous. For this simplified example, it indicates that the worst-case factor-of-safety is at an odd angle (9°) that I hadn't originally considered significant.

PROFIS Anchor,Tension Breakout,Direction-Sensitive

1 Reply
Posted by Bryan Johnsonover 6 years ago
Hilti Verified

Jonathan,

For further assistance with this matter, feel free to email our Engineering Support Team at hnatechnicalservices@hilti.com and include the PROFIS Anchor Design Report and PROFIS Anchor file, so that they could look more into this matter for you.  Let us know if you have any other questions.

Regards,

Bryan