precast wall panel attachment help

huangyhg

precast wall panel attachment help
i am currently designing a steel framed building with precast wall panels as the exterior facade (non structural).  there are quite a few windows in the building and some of the precast panels need to be hung from the steel perimeter beams.  it's approximately 800 plf of load on each beam, and is about 11 inches away from the beam centerline.  therefore there is an eccentric load occurring, which i am taking out using angle kickers to the top chord of joists/beams.  does anyone have experience with the detailing of the attachment of the precast to the beam?  an angle at the top of the beam?  one at the bottom?  any suggestions would be greatly appreciated.

in order to prevent torsion on the beam, the kickers need to be from the bottom of the beam rather than from the precast.  probably you knew that.
for the supports of the panel, i think you would need connections at both the top and bottom of the beam.  i would provide vertical slots at one location, probably the bottom, so the gravity load is delivered to the top flange, and the horizontal load is supported at both places.  for the horizontal load, two angles would work, but for the gravity load, some stiffening would probably be required to deal with the 11 inch eccentricity.
sometimes the precaster can supply a structural steel connection, which projects from the back face of the panel and loads your beam at the centerline (minimal torsion on your beam now).  the moment is taken into the panel, rather than your beam.  if the moment is too large in the panel, maybe they can locally thicken the concrete at the connection locations, to prevent cracking.
if the load bearing connection in the panel is near the top of the panel, then you need something near the bottom of your panel to prevent the bottom of the panel from coming in (a separate girt, or if your beam is deep - use the bottom of the beam flange - then you would need to check the torsion in your beam in that case.
if the load bearing connection is near the bottom of the panel, then you need a tie-back connection near the top of the panel.
and usually each precast unit has only two support points per panel.  pci design handbooks and other resources out there have a number of details.  pci even has an architectural precast handbook that has mostly details on this topic:
architectural precast concrete, 3rd edition - mnl-122-07
is there any practical detail for hanging precast spandrel. is there any link which is free.
can you make the precast panels span column to column?  then you just need a haunch off each column to support the panels.  threaded rods near the bottom of each panel can connect back to the columns for lateral loads.
daveatkins