beam chart difference between black and green steel books

huangyhg

beam chart difference between black and green steel books
hi there,
did ya'll noticed that the moments given by the black book's beam charts are generally larger than that by the green book's?
for instance on the black book, for w14x43 with 20ft unbraced length, the available moment is 109.5 kip-ft;
on the green book, the available moment is 81.5kip-ft.
anyone gotta an explaination for this, please?

black book is based on lrfd, so the listed moment is refer to factored load (combination with load factor).
green book is based on asd, basically load combination without load factor except sometimes with a 0.75 factor in some combination.
robert, that is not correct.  the black book is both asd and lrfd, and the 109.5 value represents the asd capacity.
i don't know why they're so different, without digging into the equations.  the lateral torsional buckling equations changed between the two versions, but i wouldn't have expected the values to differ so drastically.
we just noticed this the other day in comparing an w8x15. i think it was somewhere near 20% increase in capacity @ 9'-0" span, if i re  
i agree with nutte.  the difference is within the revised ltb equations.  if you calculate the numbers by hand you will get the same numbers that are in the charts (i wrote a spreadsheet for this).  as for the large difference, i would guess that it is based off more research that has been performed since the 89 spec.... and one of the reasons why to go to a combined spec.
as i understand it the aisc 13th asd numbers are the lrfd values divided by 1.5
the black book is for black steel and the green book is for green steel.
irhg, no, it's not true. the factor of 1.5 was already in the formula on the chart, i.e., mn/omiga. so you really can not apply that 1.5 one more time to the values.
also, the equations were recalibrated for the latest code to bring the results from either asd or lrfd closer together, so there is not an advantage to using one over the other.  in the previous codes, depending on your dl/ll ratio, either asd or lrfd would result in a more economic design.  i can't re  
however, structuresguy,the asd beam tables for fully braced beams for black and green books are very similar.
structuresguy-
that's not the case. the equations are calibrated at a ll/dd  ratio of about three. lower than this, lrfd is more economical.
think about this. the capacity is static. there is no way to tweak capacity based on ll/dl ratio.