Openings in Insulated Precast Wall Panels 2

[RFreund]

I have a couple general questions regarding openings in insulated precast wall panels below. I’ve included a couple examples to illustrate what my questions are based on.

[ol 1]
[li]Is there a general design guide for insulated precast wall panels? This may give me a better feel for these conditions/questions.[/li]

[li]For out-of-plane loading, is there any load sharing assumed between panels for concentrated loads or openings? Similar to what is done for hollow core plank. My assumption is no, because there is typically no connection between panels (except maybe for alignment), but I might be wrong here.[/li]

[li]If you have a 30’ tall wall x 12’ wide wall panel and you have an 8’ wide x 6’ tall window (top of window say 9’ off the ground). When you design the panel, are designing the panel assuming that you have a 2’ wide pier that is subject to a uniform wind load or are you taking advantage of the fact that you have a full panel above the window?[/li]

[li]Existing suspended panel - say you have a 6’ wide panel that is 30’ tall and it has the same 8’T x 6’W opening, so that panel is really more of a deep spandrel. On the surface it seems plausible that these openings could be made without installing some sort of steel lintel. The panel should be capable of spanning horizontally based on the original design and as long as there is enough panel depth to support vertical loads, then it would seem plausible.[/li]

[li]From a schematic perspective, I would say that existing panels with full width openings (i.e. are now suspended/spandrel panels) would require some sort of steel H-Frame. See image below:[/li]

[li]For cases 3 and 4 above if you have no reinforcement information about the panel. Does it seem reasonable that you could grout a bar in the bottom of the panel and check the panel for bending in both directions using just the bar grouted at the bottom of the panel (with the full panel depth) (see image below):[/li]

[/ol]

Thanks in advance!

EIT

http://www.HowToEngineer.com

 

[KootK]

1. Is there a general design guide for insulated precast wall panels? This may give me a better feel for these conditions/questions.

Start here: Link. It doesn't deal with openings really though. If there's a good design manual for prestressed wall panels that does, I've not found it. A lot of the best guidance for opening treatment seems to be found in the tilt--up panel documents for some reason.

2. For out-of-plane loading, is there any load sharing assumed between panels for concentrated loads or openings? Similar to what is done for hollow core plank. My assumption is no, because there is typically no connection between panels (except maybe for alignment), but I might be wrong here.

Generally no load sharing.

3. If you have a 30’ tall wall x 12’ wide wall panel and you have an 8’ wide x 6’ tall window (top of window say 9’ off the ground). When you design the panel, are designing the panel assuming that you have a 2’ wide pier that is subject to a uniform wind load or are you taking advantage of the fact that you have a full panel above the window?

You'll design pier strips as you suggest and they will usually continue throughout the panel height. You are often taking advantage of the full panel width areas for limiting pier buckling heights etc.

4. Existing suspended panel - say you have a 6’ wide panel that is 30’ tall and it has the same 8’T x 6’W opening, so that panel is really more of a deep spandrel. On the surface it seems plausible that these openings could be made without installing some sort of steel lintel. The panel should be capable of spanning horizontally based on the original design and as long as there is enough panel depth to support vertical loads, then it would seem plausible.

Usually the panel self-spans and there isn't a separate steel lintel. If aesthetics allow it, a shoulder condition at the top corners of the windows is cheap and easy. It jogs the panel joint there though. The other common meathod is to hang the panel from a hidden, inverted steel corbel connection at the very top. Basically short HSS cantilevered out from the suspended panel.

5. For cases 3 and 4 above if you have no reinforcement information about the panel. Does it seem reasonable that you could grout a bar in the bottom of the panel and check the panel for bending in both directions using just the bar grouted at the bottom of the panel (with the full panel depth) (see image below):

I've not seen that detail before. Some concerns that I would have include:

1) As a very deep beam, by the time that reinforcing gets mobilized, cracking in the wall will be atrocious.

2) I'm not sure how one would ensure bond between the new grout and the existing concrete wythes.

3) Even with the reinforcing in play, you'd need to do more to drag that load up to whatever is functioning as the "support". If you're cutting out a full width panel, it's not like you'll be sawing in a shoulder joint.

4) Underside grouting seems difficult and prone to quality problems.

 

[RFreund]

Thanks for the responses.

Regarding Point 6 (the deep beam check). How are these usually designed for new panels? Are the ACI provisions for deep beam used? Do you have (2) 3" thick beams or (1) composite beam? Intuitively it seems like an 8' deep concrete beam spanning 8' doesn't even need to be checked. However, it's always nice to put numbers on paper.

EIT

http://www.HowToEngineer.com

 

[KootK]

I'll design the panel as a deep beam to determine reinforcement but then, also, design the beam such that it doesn't crack under service level loads and lifting/shipping. It's this latter requirement that is the most critical. I'll usually go two 3" beams unless the panel bottom is solid at that location.