Detailing of Pin ended Connection Reinforced Concrete Column 1

[StrucutreDr]

Hello Everyone,
Can any body provide reference to the detail of pin ended connection of reinforced concrete column?

 

[JedClampett]

Even when your analysis assumes a pin ended condition, there is some fixity of concrete columns due to the construction techniques used. Why do you want a detail like this? You can assume pin ended and have the reinforcing consistent into the support. It ends up with a more conservative design.

 

[JAE]

For a true pin - my imagination immediately went to a concrete column with a steel jacket at its end - attached to the column with deformed bar anchors extended up into the column. Then off the bottom steel plate, create a true finger plated pin with a steel pin. Very expensive and to my mind awkward.

 

[JedClampett]

I've seen pins built into wood arches (I think I've seen them in concrete arches, too, but I can't remember where), but I think you need a pinned end condition or else your analysis is invalid. As JAE says, it's a pain for zero benefit.

 

[rowingengineer]

There are sliding base connections which are close to pinned. These friction base isolated connections are sometimes required for earthquake considerations ie a sliding base ect. I would recommend reviewing earthquake isolation devices for more information.

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[asixth]

Why would you like a pin connection for? A precast column is the only one which comes to mind. A column on pad footing would also have minimal capacity to transfer moment as well.

 

[StrucutreDr]

Aramco Specification requires pin ended concrete column details. Please check the attached sketch of detailing of pin ended reinforced concrete column.
Is it ok to detail a reinforced concrete column like this? The spalling of concrete at the pin location shall be protected by concentration of stirrups at the location.

 

[Enhineyero]

If you want to have theoretically pinned column, then detail it in such a manner that it will not develop the required tension anchorage bond (eg. no hooks with short embeddment of the starter bar of your column to the footing). different codes have different formula in computing this. or as asixth said use precast elements.

 

[slickdeals]

The way you have drawn, the bars will clash. If you do go this route, make sure you stagger the bars when the criss-cross.

Can you give more information on the specific detail and where it is intended to be used. I am sure ARAMCO would have a reasoning behind doing this, other than just stating this. It is a difficult detail to build.

 

[StrucutreDr]

slickdeals
yes the main reason for using a pin ended connection is to obtain a stiffer super structure. In fact the isolated footing is never fixed end condition.
And definitely the bars will be adjusted to avoid the criss-cross.
The column will give partial fixity in the other direction.

 

[Archie264]

Do you think they (the spec writers, that is) intended for it to apply to concrete? With steel I certainly agree with requiring pinned bases unless an approved moment-resisting base connection is used. But with concrete it might seem less applicable...

By the way, I do understand where the spec-writers are coming from, I think. I've seen many cases where finite element models were made to "work" by the user inputting unrealistic fixed base conditions. It can make a lot of your problems go away...during the modeling phase, that is, only to reappear during the reality phase of the project when the spaghetti-noodle structure gets blown down in the wind.

 

[JedClampett]

You're likely violating the clearance criteria of ACI at the most critical section of a column. You definitely don't want a rock pocket or poorly consolidated concrete at the base. I'd analyze as pinned and design traditionally.

 

[TXStructural]

The pin fixity is about small movement, not gross movement, until we get to seismic detailing. At a footing, the notional fixity is pinned, but not the actual fixity. The use of isolated footings provides the degree of rotation needed to use pinned fixity.

The proposed detail is not useful. If you were going to detail the connection between the footing and column to allow rotation under large deformation of the superstructure, it would require significantly more complexity. Even with dowels only along the central axis of rotation, it would require either debonding of dowels (and potential displacement of the column) or crushing of the concrete, in order to activate the hinge/pin.

Designing with pinned fixity at a footing yields a stiffer and stronger structure (as previously mentioned) and any fixity provided by the foundation element will add to stability but is not be required. It is a mistake to think that an actual pinned condition is necessary. That said, if the footing is at one level and then a slab is installed higher up on the column, excessive fixity may well be a problem. You can end up with a stiff column that is not strong enough.

 

[hokie66]

I think that there is a confusion here between analysis and design. Just because the frame is required to be analysed with pinned bases is no reason for detailing (designing) it that way.

 

[StrucutreDr]

@ TXStructural
Can you please elaborate
"That said, if the footing is at one level and then a slab is installed higher up on the column, excessive fixity may well be a problem. You can end up with a stiff column that is not strong enough".