Pipe Column Transition
Pipe Column Transition
(OP)
I have been working through the design on a single pipe column fixed at the base to a circular concrete pier. The column is 42" in diameter. I am having some trouble with the anchorage with regards to concrete bursting on the anchor head. This is being controlled by tighter than normal anchor bolt spacing. I am locked in with the 42" column because of an attachment up above requires that geometry. In an effort to improve the situation (going to larger and less anchors is not helping the situation enough and I like the redundancy of the multiple anchors) I would like to step the column diameter out to 54". Does anyone know of a design guideline or standard that covers steps in pipe columns subject to axial load, moments, and shear? I am trying to steer clear of a conical transition due to fabrication issues and lack of confidence with this having a good fit up when finished. Loads are being introduced by a slewing bearing roughly 60" above the base plate connection so we don't have a ton of room to make it all happen.
On another related issue, I can satisfy the bursting requirements if we use a template ring. If we account for a 10 degree wedge (the anchors are 1 3/4" on 10 degree increments) for the bearing plate (about a 5" segment) we can get sufficient bearing area to fully develop the 1 3/4" A-36 anchor. What are people's thoughts on a roughly 5"x6" bearing plate being stiff enough? I am basing the design criteria on ca1 being limited by anchor bolt spacing/2 as recommended in some research I have dug up on anchor bolt design into caisson foundations?
Thanks in advance for any thoughts.
On another related issue, I can satisfy the bursting requirements if we use a template ring. If we account for a 10 degree wedge (the anchors are 1 3/4" on 10 degree increments) for the bearing plate (about a 5" segment) we can get sufficient bearing area to fully develop the 1 3/4" A-36 anchor. What are people's thoughts on a roughly 5"x6" bearing plate being stiff enough? I am basing the design criteria on ca1 being limited by anchor bolt spacing/2 as recommended in some research I have dug up on anchor bolt design into caisson foundations?
Thanks in advance for any thoughts.






RE: Pipe Column Transition
See the paper in the link - you can get away form limits due to breakout and sideface blowout, which may be enough to get it to work.
http://www.google.com/url?sa=t&rct=j&q=&am...
RE: Pipe Column Transition
I've seen the steps on big billboard and sign posts, but have no idea what design or detailing went into them.
Maybe a stupid idea, but can you put a boiler-type manhole in that column and then put anchors both inside and outside?
RE: Pipe Column Transition
RE: Pipe Column Transition
It sounds as though you've moved past the pipe transition business. If not, this book has a version of the sign structure column stepping detail that JStephen may have been alluding to: Link. I have a copy at home. If you're still interested, let me know and I'll scan it 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: Pipe Column Transition
In regards to the anchors, have you ever looked at the thread bars in fatigue? I've got some low cycle fatigue, which is partially controlling the anchor bolt design and I'm limiting the stress to 7ksi for a the total range. Fairly decent little problem to address all this stuff!