PCI Connection Details

[tclat]

Hi,

The PCI connections manual shows a detail for connecting a precast column to a footing using a socket which the column sits in and is grouted. No shear connectors or bars which extend out of the concrete.

I am in a seismic area and while I don't have any net direct tension in my columns I'm a bit concerned but not having a positive connection.

I've been searching the PCI design manual and ACI for recommendations on minimum connection requirements but haven't found anything.

The contractor certainly prefers this connection detail compared to bolting or welding the column to the footing via embeded plates.

Am I being too cautious here? Any thoughts

Thanks

 

[JD2]

A typical detail that we used (and can be found on page 5-28 of the 2nd Edition of the PCI Design Handbook) had a typical foundation detail (embed bolts, concrete ties, etc) as if for a steel column. A steel baseplate was cast to the bottom of the pre-cast column (it was attached to the precast column by rebar welded to the face of the base plate which extended up into the precast column and lapped with the main bars in the column). The base plate could be oversized so that the anchor bolts were outside the footprint of the precast column so the nuts could be installed without interference or they could be located within the footprint of the precast column and the bottom edges of the column blocked out to allow nut installation. Haven't worked with precast in awhile so I'm not sure if the detail occurs in a more recent edition of the reference. In the end, the connection was as if you were erecting a steel column.

 

[Prestressed Guy]

That connection is still found in the 6th addition of the PCI Handbook and a design example is given in section 6.12. This is a good connection if you need significant uplift or moment capacity from the connection. If all you are trying to do is provide code required continuity, steel embeds in the column and footing connected by weld angles is cheaper with greater erection tolerance. In SDS D and above you cannot use the socket because it does not meet the minimum continuity requirements.

 

[tclat]

I'm also familiar with the connection like a steel column connection.

The advantage though of the socket type detail is the higher moment capacity at the base on the connection.

The structure in question sits on these columns and has no shear walls and in essence will function as a cantilever column system.

Are you in a seismic area?

 

[Prestressed Guy]

I design mostly in SDS D and here we need to have a continuity tie to the footing. You could probably meet that requirement by casting a shear lug in the socket and the sides of the column below the pour back but i have never done that.