Precast Panel Deflection 1

[haynewp]

I have a 2 story office building with a precast concrete panel band around the entire bldg at the second floor. Above and below is storefront. What would be a good vertical deflection criteria for the adjacent floor beams that support these panels? I usually keep L/600 for masonry in this situation.

 

[jheidt2543]

Here are a few thoughts:

1. I think there is more concern about the absolute amount of deflection then the L/600 criteria. It would be possible to meet your L/600 and still have enough absolute defection to crack your storefront glass.

2. I would talk to the storefront supplier or engineer and find out the maximum amount of deflection the system could tolerate and limit your precast deflection to some FS less than that.

3. Another approach would be to supply the storefront engineer with the amount of live load deflection you expect. Then he would have to design his system to accomadate it. Live load deflection because the dead load deflection should already be set at the time the installer field measures for the storefront. BE SURE THEY FIELD MEASURE BEFORE FABRICATION!

Just my two cents, good luck!

 

[ADT]

Yes, what is this P/C band supporting? Is it purely a cosmetic device?
The support of glass, as mentioned, can be a real issue, but this will depend on the jointing and physical construction of such frames. Check the actual frame joint methods, eg. rubber inserts, silicone with little structural long-term flexibility, etc.
Actual deflection of the P/C member might however be fairly small, I would think, if it is "bending" about it's narrow dimension axis.

So many questions ... so little time!
Give us some more details if you need some extra feedback. Anthony Tugwell
Project Director & Consulting Engineer - now in Australia

 

[ruiscpt]

ypu must account for the so called active sag.
depends on deformations induced by creep and retractions "AFTER" the instalation of the pannel.
plus the live load deflections.
So u must know the value of the active sag to prevent enough space for these deformations