Concrete gravity only columns
Concrete gravity only columns
(OP)
Hi
Any ideas on how to achieve pin connection at the top of an interior column and rigid concrete beam? My intention is to have that interior column not to resist seismic lateral forces. I know you can never truly have actual pin connection in concrete members but for the practical purpose of design, how do you achieve pin connection at the top of the column construction wise? Would that include not bending the beam bars into the column and just let them pass through the core without bending them into the column?
Thanks
Any ideas on how to achieve pin connection at the top of an interior column and rigid concrete beam? My intention is to have that interior column not to resist seismic lateral forces. I know you can never truly have actual pin connection in concrete members but for the practical purpose of design, how do you achieve pin connection at the top of the column construction wise? Would that include not bending the beam bars into the column and just let them pass through the core without bending them into the column?
Thanks






RE: Concrete gravity only columns
If only rotational - then perhaps do a precast concrete-like connection where the beam sits on an elastomeric bearing pad.
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RE: Concrete gravity only columns
Thanks
RE: Concrete gravity only columns
Thanks again
RE: Concrete gravity only columns
1. Build the concrete column up to a point below the bottom of the beam - perhaps 3 inch gap.
2. Supply a vertical smooth dowel in the center of the column sticking upward some distance.
3. Install an elastomeric pad bonded with a teflon/slip material on top. Usually there is elastomer/stainless steel plate/teflon in the assembly. This is the bottom plate.
4. The pad/slip plate assembly would have a slotted hole in the center for the dowel.
5. Install over the bottom assembly a top teflon and steel plate assembly such that the teflon pads are in contact.
6. The upper assembly is usually larger than the lower assembly - the overhang keeps dust and debris from accumulating on the lower pad and possibly gouging the teflon over time with movements.
7. The upper assembly would have headed studs sticking up to bond into the concrete beam above.
8. Install an open PVC tube over the dowel - sized to allow the horizontal movement in the beam you expect. PVC tube to have a top cap of course.
9. Cast the upper concrete beam over the pad assembly and the PVC.
Even with this there is still some level of friction (teflon or other slip materials are not perfectly smooth). That means that your "gravity-only" column will still have some lateral movement due to the beam's horizontal displacement.
To account for this you'd have to perform a deformation compatibility analysis on the column....assuming some degree of lateral delta at the top.
Since you have to do this in any case, I would recommend ignoring steps 1-9 above and simply use an elastomeric pad to take out most of the rotational moment forces and design the gravity-only column to be laterally displaced at the top by your frame Delta displacement. Simply back-calculate the moment that would be produced in the column by this lateral displacement and design for the Pu and Mu forces you get. Chances are it may be that the columns minimum 1% steel reinforcement is adequate anyway.
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RE: Concrete gravity only columns
Thanks a lot!
RE: Concrete gravity only columns
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RE: Concrete gravity only columns
1. Why don't you want the columns to resist those forces? Why are you creating a pin connection?
2. What type of building is it? A single story project?
3. As JAE was asking, is this in a higher seismic zone?
RE: Concrete gravity only columns