precast bearing on grade beam

huangyhg

precast bearing on grade beam
i have a 12,000 lb 6" thick precast panels that will bear on my continuous grade beam.  assuming during erection there will be two bearing points that will each take 6k.  the ledge (like brick dap) is 6" wide so panel bearing will be centered as close to edge of concrete as 2 1/2 inches.  let's say they use 4" bearing plate, what kind of shear failure plane would i be looking at?  similar to corbel analysis?  
tw
to avoid the problem, put in temporary metal shim plates at 4 foot centers until the wall can be continuously grouted between it and the strip footing.  no worries.
mike mccann
mccann engineering
is the bearing direct onto the grade beam, or are bearing plates cast into the grade beam? while a loose bearing plate theoretically spreads the load at the bearing point, in reality the plate sits non-uniformly on high points.  you may want to use elastomeric or similar bearing pads to be sure you are spreading the load as designed at each of the two main bearing points. if you assure transfer, then you can lengthen the bearing plates. that will help a little.  you could also have. at each bearing point, two shim stacks about 18-24" apart with an adequately thick steel plate between them. that would spead the load.  
intermediate shim points present a similar issue in that the load, at least at some moments during installation, will bear only on two points (thats what defines a straight line - the panels will not deform to put load on the added points).
first, you need to check if your bearing has enough area that will not cause bearing failure in the ledge or in the grade beam.
secondly, you can use shear friction analysis to design the reinforcing for the ledge.
you also may need to increase the load to allow for any sudden impact during erection.