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Re: Equivalent frame

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Mr. Bryson is absolutely right.  Even when we go the old Winter/Nilson method, we are providing for the load to be carried in both directions.  X-moments in slab plus bending moment in cross beams equal W.Lx/8 and Y-moments in slab plus bending moment in longitudinal beams equals W.Ly/8.  This is what Equivalent Frame is doing.
 
 
 

Michael Bryson  wrote
 

My experience has been that the equivalent frame method gives very close
results to that of a FEM method used by a program such as SAFE. In fact
from equilibrium, the full load must be carried separately in each
direction (cut a panel along the points of zero shear so that it is
centered over a column). As stated by someone earlier, the FEM just gives
you a distribution of the forces along the slab width.

I don't think that analyzing the slab twice in two different directions
corresponds to designing for twice the load. If that was the case, nobody
would design using the equivalent frame method. I think it just means
doing two checks to make sure it works, but not adding the results of the
checks together.

S. A. Masroor