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In article ,
says...
Proctologically Violated©® wrote:
How did you determine what an "acceptable" deflection would be? Building
codes?

i personally use the moment and bending stresses , and a safety
factor of 3 to four , with 36000 psi being a standard for most beams you
dont want to get over 9 to 11 k in the bending and moments

The AISC standard uses a factor of safety of 1.67 in most cases, which
results in a working stress of 21.6 ksi for A36 steel.

you will
see deflections of less that 1/16 inch for a properly designed beam ,
while anything over 1/8 inch you will see the bending and moment
stresses edgeing up into unacceptable levels

That's a huge oversimplification. A deflection much greater than 1/8" is
acceptable in a long beam, and a very short beam may fail, probably in
shear, before it deflects 1/16".

Ned Simmons