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Steel Interchange


CB Section
I am working on a rehabilitation project. Per the drawings, the steel dates from the late 1920s. There are members identified on the drawings as 12" CB 120#. Would it be reasonable to consider this beam section to be similar to a W12 X 120?

Answer
I do not believe that there were any 12-in. shapes rolled during the 1920s that weighed 120 plf, but you can find such listings in one of the historic shape references developed by AISC. Steel Design Guide 15 is a reference for historic shapes and specifications. There is also an AISC Shapes Database v13.1.1 and 13.1H, where the H stands for Historic. Both references are available as free downloads for AISC members at www.aisc.org/epubs, or can be purchased by others.

The CB means that it was is a Carnegie Beam, so I would start there. I wonder if the draftsman of the time had perchance reversed the numerals in the beam depth, as Carnegie did produce a 21CB120 at the time. I would suggest first checking the beam measurements to see if it may be a 21CB120.

Kurt Gustafson, S.E., P.E.

Posted on August 1, 2010


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