Pour Stips for Tilt Up Buildings

[zlindauer]

I am working on a building that will be constructed using tilt up concrete sandwich panels. The geotechnical engineer has recommended a foundation consisting of a slab on grade stiffened with grade beams. I am trying to figure out if I need to use a pour strip for this type of foundation, or if I can simply create a deep wide ledge on the exterior beams to set the pannels on.

If I don't use a pour strip will the edge of the foundation be likely to be damaged during placement of the panels?

Is the pour strip critical to proper anchoring of the base of the tilt up panels, or are there acceptable methods that don't require a pour strip?

Is there a good resource you can recommend that would show various types of base connections between tilt up walls and their foundations?

Thank you!

 

[rowingengineer]

The pour strip is not required for all buildings, it is possible to cast a recess in the top of the beam and land the panel without structural damage to the beam. I would normally like 2-3 inch recess, with a sealer to water proof.

ANY FOOL CAN DESIGN A STRUCTURE. IT TAKES AN ENGINEER TO DESIGN A CONNECTION.”

 

[Lutfi]

The best reference on tilt-up panels is a book called “The Tilt-up Design and Construction Manual” by Hugh Brooks. I strongly suggest you get a copy of it. It addresses all types on issues with tilt-up construction plus worked example, specification section and much useful detail.

A copy of the cover is attached.


Regards,
Lutfi

 

[csd72]

Depending on your local building code, the pour strip may be required to prevent outward collapse of the panel during a fire. If this is the case then you can use a much deeper recess with embedded plates at the top to form a moment connection.

Also remember that the panels will be installed initially on two shims so your ledge needs to be able to take the load from this.

 

[zlindauer]

Thanks for the responses. I wish I could fix my spelling error in the thread title, but oh well.

I do have the Hugh Brooks book, but he doesn't include a foundation detail for a stiffened slab foundation. Some of his other details are quite handy, though.

Here's another question for the tilt-up experts out there:

My project has a double-height space where the architect is proposing cast in place concrete columns and glazing in the lower half and tilt-up panels for the upper portion of the space. The upper tilt-up panels have a seam at the centerline of the columns so that each panel gets half the column width for bearing at each side. The architect would like the columns to be 14" wide.

Would you insist on having a cast-in-place beam at the tops of the columns so that the panel has a consistent surface to bear on, or would you allow the panel to be supported only at the lower corners? So far I've told the architect I want him to add a beam, but I know this is definitely not his preference.

Your feedback is very much appreciated.

 

[csd72]

The beam wouldnt do much as the panel would be much stiffer.

I would suggest that you look at the bearings in detail as these will definately be the critical item. It is common to use corbel like details at the corner to prevent it cracking off under the bearing stress. Bearing development at the top of the column is also tricky.

Check the column for the eccentric load of one panel during construction.

Construction method is also very key here.

 

[zlindauer]

I've included a PDF of an elevation of the wall in question.

I suggested a corbel, but that didn't appeal to the architect. The idea of the beam was to basically get the benefit of the corbel without changing the geometry of the look he is going for. My proposal is to replace the strip at the bottom of the beam just below the openings with a cast in place beam. The architect has accepted this, I just wonder if it would be possible to give him what he wants and cast these panels as he shows them.

 

[csd72]

Have you considered steel columns with an FRC surround? Can be rendered to match. Alternatively they can be composite columns.

Either way it is then possible to have a cap plate that can be welded to embedded plates on the underside of the panels.

I was not suggesting to put in a corbel, rather you need to analyse the corner of the panels like a corbel.

 

[zlindauer]

I hadn't considered that. Thanks for the suggestion.