Precast concrete wall panels - renovation/upgrade

[lrhg]

I am working on conversion of a one story warehouse structure into an elementary school. What started with supporting new RTU's now requires that we upgrade the building to current code (IBC 2006). The original construction was under BOCA - no seismic design required at all. The code upgrade requires seismic design cat. B, which controls over wind. The lateral system of the building is precast wall panel and the architect has to provide windows in the building for its new use. We've had no luck locating the 10 yr old precast panel shop drawings, so we're planning to spec some testing, including cutting panels to see what we are working with.

Please share any experiences/advice with similar situtations.

 

[youngstructural]

It would be a mistake to consider any panel really representative, unless this is a truly featureless box building. Testing can't hurt, but my first port of call would be the original design engineer.

I have only ever relied on existing panels when I had drawings to tell me what the reinforcement was, or else have simply considered the raw concrete and have strapped with steel for the increased ULS case load.

I will be very interested in others' postings!

Cheers,

YS


B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[JStructsteel]

Some other things to find out are if the panels were post-tensioned. That can limit to where you put openings, without reinforcing the panels. Additionally, adding openings could change the deisgn of 'whats left' after you cut the opening.

 

[Rjeffery]

Ground Penetrating Radar (GPR) has been used successfully to locate and size reinforcing steel although not to identify type (ie cable vs. rod), Radiorgraphy could do that for you, but that poses hazards...

The best way to test something is to squeeze it, slowly, until it breaks!

 

[JAE]

I just posted this link in another forum. It deals with required seismic application for tilt panel walls, but might apply a bit in your case:

http://www.structuremag.org/Archives/2008-1/C-StructPract-Steinbicker-Jan08.pdf

 

[lrhg]

Thanks so much for your replies!

Here's what we know:
1. We have the orginal design drawings. The building is basically a box with the exception of some loading docks.
2. There really are no true "structural" drawings. The roof framing was done by the architect and there is no design cirteria for the lateral load resisting system.
3. There is a line of perimeter steel columns carrying the roof loads - i.e the panels are not load-bearing.
4. We expect that these are prestressed insulated wall panels - though none of the local precasters will claim the job.

My initial thought was GPR (though I don't know how we coudl measure the prestress)to locate the reinforcement and size of insulated cores. And of course, concrete cylinders.
to be honest, I would like to just add some steel bracing inside the panels where we have no new windows to take care of the lateral and deal with the windows by adding a steel frame to the inside. The owner, of course, doesn't want the expense.

 

[csd72]

when you cut holes in the panels this will reduce their ductility as there will be no trimmer bars around the edges. You may need to discount any cut panels from the seismic lateral load resisting system.

I would assume the minimum steel allowed in the year it was built and mark it to be verified in field. This will be easy to do on the first panel that gets cut and then can be checked on other panels for consistency.

 

[JStructsteel]

If you are changing any of the flashing, etc, you should be able to see if they are post tensioned or pre-stressed, unless they were looped. Might even saw a couple inches off to see if you can see the reinforcing, just be carefull if post-tensioned.