Old AISC Light Beam (B) Section Properties
Old AISC Light Beam (B) Section Properties
(OP)
I have an old structure and the existing structural drawing calls for a beam section 18B40. I have looked into my AISC STeel Manual 6th Edition and found that it is not listed under the "light beam" section nor the WF section. In fact, I was unable to find any 18" beams with 40 plf weight.
Could the existing beam call out be in error?
I would like to know if 18B40 are equivalent to modern W18x40.
Thanks to all in advance.
Could the existing beam call out be in error?
I would like to know if 18B40 are equivalent to modern W18x40.
Thanks to all in advance.





RE: Old AISC Light Beam (B) Section Properties
whyun,
AISC Design guide 15 covers historical sections.
Printed out, the design guide is over 300 pages long.
From previous experience with historical sections, I'd say 18B40 sounds like a correctly called out section size.
This is a link to the download page, but you have to be an AISC member to download for free.
h
It helps to know the approximate year the building was built to tie down the correct section properties.
Regards,
JPJ
RE: Old AISC Light Beam (B) Section Properties
RE: Old AISC Light Beam (B) Section Properties
I do have a sixth edition. The wide flange sizes for the 18" deep sections starts with 18WF45. The largest B section in the manual is 16B31. The drawing calls for 18B40.
I've compared 16B31 and W16x31 and found that the dimensions are roughly equivalent and S and I are "very" close. Thus, my educated guess would be that 18B40 and W18x40 can assumed to be the same.
VirtualEngineer: Thanks for the link. Unfortunately, I am not a member of AISC. I do have a AISC Sections Database CD that came with LRFD 3rd edition. I will look there.
Thank you, both.
RE: Old AISC Light Beam (B) Section Properties
www.SlideRuleEra.net
RE: Old AISC Light Beam (B) Section Properties
I will go home and look for my AISC shape database CD and find out. Thank you all for reassuring me that I am not overlooking something.
RE: Old AISC Light Beam (B) Section Properties
Perhaps it is a mistake in the existing drawing (?)
How was it ever approved??
Anyways, thanks everyone.
RE: Old AISC Light Beam (B) Section Properties
Usually when I field measure a member, Depth, Flange Width and Flange Thickness is enough to identify the section.
For an older shape, take notice if the flanges are sloped.
It was very common for older section web thicknesses and flange thicknesses to vary considerably from the design thickness, generally on the conservative side.
Best of Luck,
JPJ
RE: Old AISC Light Beam (B) Section Properties
http://www.steeljoist.org/publications/