Tilt Panel Opening

[NewbieStruct]

I am assisting in the design of a tilt panel building. The building has a 7.25" tilt panel that is 39' long and 18' tall with a 3' parapet. There is a 34'x12' opening in the panel with 3' and 2' pilasters on either side.
Are there any restrictions with the size of the opening in a panel? I am getting double mat reinforcement with ties at the jambs and I am designing the opening as deep concrete beam. In addition, I am also bracing the opening at the ceiling height to the joists. The panel also is OK in terms of deflection per ACI 551. The vertical stress in the pilasters is also OK.

Is lifting going to be an issue for this panel?

 

[OHIOMatt]

If I were designing the panel, I would approach it in a different manner if possible. A 39' wide panel may require specialized rigging to lift, in addition, it will likely require stiff-backs to prevent the panel from cracking during the lift since you end up with such small jamb areas. I would see if it would be possible to extend the adjacent panels to the opening, and then set a spandrel on bearing seats in the adjacent panels.

 

[NewbieStruct]

The panel is corner panel on the left and the panel adjacent to it on the right has the same situation (for the adjacent panel, the opening is 16').

 

[ztengguy]

So a 90 degree connection (maybe a ledge for it to sit on) on one side, 4' wide on the other side. Now your spandrel is only 6' tall, and can get away with edge lifting it up, and set at the same time.

 

[spats]

I'm going to have to disagree with the spandrel concept. You would likely need to seat the spandrel(s) on the "leg", cutting into it's structural width. The "leg" would need to resist the lateral load from at least the lower half of the spandrel(s), because of the discontinuity that you created (only the "leg" can span). At the same time, you've weakened it considerably.

 

[NewbieStruct]

My boss is going to talk tp the architect and the project contractor's tilt panel sub to figure out the best course of action..

 

[hokie66]

Sounds to me like you need more thickness in the jambs.

 

[a2mfk]

Ditto Hokie66, but Newbie said the design is a deep concrete beam?

Key thing Newbie that you have already done- get your boss involved, those are good questions for your mentor. This is not a cookie cutter panel by any means.

Also if all of your panels along that wall are the same, you may have some in-plane shear wall issues that you will at least need to pay attention to.

 

[hokie66]

a2mfk,
I think the "deep beam" refers to the 34' long x 6' deep head section. But the legs of the panel, 12' high, 2' wide, and only 7.25" thick, are the big problem with both strength and ability to erect. He talked about two layers of reinforcement and ties in those skinny legs, and I don't like the sound of it. Even if you could satisfy the in place strength provisions and get it cast, the legs would crack during erection unless cast on a tilting bed.

 

[NewbieStruct]

We talked to the architect and managed to increase the legs a little bit. The height is lowered to 9'-0 too. The legs are now 2'-6" and 3'-2". The panel works on paper but I was concerned about its erection during construction. We are going to talk to tilt contractor later this week and see if he thinks he can do it. If not we are probably going back to the architect to change the panel. This is the only big panel, other panels have 2'-0" legs with 9'-0" openings as well as no opening panels.

 

[a2mfk]

What hokie and I are saying is it seems this will work as you originally stated- if you can thicken the panel legs. Two layers of bar with ties in only 7.25" just isn't feasible, the rebar is all crammed in there and your depth of steel for bending is quite small. Especially since it sounds like out of plane lateral loading is the main problem, since you have solid panels along the same wall which will attract all the in-plane wall shear from the roof. It is like you have two columns and a deep beam in a moment frame, but almost no moment, just out of plane forces...