We will be checking some existing steel I beams and channels for a building in Chicago area built in 1916 for 2-3" of additional light weight topping. From the historical steel area it appears that Fy used was likely 24 ksi. The beams are fully braced. I am trying to figure out if I need to use the green book or the black book for steel check. I don't know what allowable Fb would they have used back then, 0.66 max may be?
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1916 structural steel 3
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If you have a confident Fy and the material is in good condition, you can use the most recent ASD or LRFD analysis methods and reduction factors. You are going to get better and more realistic load carrying capacity with AISC ASD than with historic working stress values. However, if you are trying to be quick about it, 66% of Fb is reasonable: AASHTO uses .75*Fb for all steel types from 1905 to present for compact/braced sections in operating value. They use .55Fb for inventory rating; I would say that your value in between could be OK. But seriously, if you are trying to get everything you can, use the black book allowable strength design methodology with a known Fy.
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BA, thanks for the link. This is great wealth of info.
a7x: The applicable code is the black book, so even though green book might give me more conservative results, but since black is the current code and I'll use that.
dik: great point on the welding issue.
a7x: The applicable code is the black book, so even though green book might give me more conservative results, but since black is the current code and I'll use that.
dik: great point on the welding issue.
msquared48
Structural
In the 1934 AISC Coce, the yield point of the steel was at 33 ksi (pg 266), but the rivets at 28 ksi (pg 271)...
As a side note here, and I never noticed it before, on pages 284 through 286 of the same AISC code, it gives the standard timber beam/column allowable stresses and dressed sizes for the time... Odd, but it is there in the steel code...
Mike McCann
MMC Engineering
As a side note here, and I never noticed it before, on pages 284 through 286 of the same AISC code, it gives the standard timber beam/column allowable stresses and dressed sizes for the time... Odd, but it is there in the steel code...
Mike McCann
MMC Engineering
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