Concrete tilt-up wall panel question

[wcg89]

Tilt-up wall panel specs:
12'w x 24't x 6.5" thick
#4 @ 12"O.C. horizontally
#6 @ 10"O.C. vertically

The cut will be made on a panel along the North Wall of the building, there are 11 panels on this North end, the panel that will be cut is panel #5.

I should also mention that the North side of this building has two levels of tilt-up panels and this cut will be made on the top level.

I have the original plans for the building from the early 80's on PDF, but the design for the wall panel is pretty vague and the plans are hard to read as it is because the plans are old and whoever scanned them in long ago didnt do a very good job.

Each panel has three plates in them vertically along both sides, the panels are welded together at these plates.

Like I said the original plans are hard to read, but by observation of the building it seems that the wall panels are not holding up the roof of the building. There are steel I-beams at the corners and several cross members all the way around the building holding up the roof.

The cut will be a 55 1/4" sq. and 8' from the floor to the bottom of the hole.

As you can probably guess, I am concerned that once the hole is cut and there is that much rebar being cut out of the wall, that the wall will fail and buckle at the hole.

I am looking for guidance on how to ensure that this does not happen, at first I was just going to reinforce the opening with 3/16" thick angle iron, anchored to the wall on both sides and welded together inside the opening. Will this be enough? Do I just need to beef it up to thicker angle iron? Or should I run a couple of steel beams from the floor to the ceiling up the wall?

Thanks for any help!

 

[KootK]

Assuming that you're right about the panels not holding up the roof, there should be no danger of buckling as there would be little axial load in the system other than the self weight of the panels. And there would be plenty of concrete panel above the opening to function as a header. The panel may, however, still need to be vertically reinforced either side of the window to resist wind and earthquake loads.

Another issue is whether or not the panel is part of a shear wall system intended to stabilize the building laterally. Those three connectors could be there to transfer shear from one panel to the next. Conversely, they might just be there to keep deflection gaps from forming between panels. Losing one panel out of eleven doesn't see too terrible though. Do you see cross bracing or anything like that behind the wall?

Where within the panel will the opening be? If it were centered on a panel horizontally, that would be great.

The panels are pretty slender at 24' tall and 6.5" thick. Might they actually be hanging from the steel roof beams?


I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[wcg89]

Thanks for your reply KootK, whe I first started looking at this, I thought the same thing that there would be plenty of concrete panel above the opening to serve as a header.

I am not too worried about an earthquake since I am in north Texas. Ha! We don't get very heavy winds here either but being on the northern side of the building, wind could possibly be an issue during storms and such.

there are cross braces on the exterior of the building, but it seems that they are for roof support.

I forgot to put the horizontal measurement for the opening. It will be centered on the panel, and 8' from floor to bottom of opening.

I don't believe the panels are hanging from the roof, but I also was not looking for them to be. I'll have to check to make sure, but like I said I doubt they are.

 

[JAE]

I think you should hire a structural engineer to help you with this.


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[Stenbrook]

I agree, you should definitely consult a licensed structural engineer with this. It'd be better to spend the money to get it checked out and done right than to have something go wrong.