QUESTION REGARDING 18B40 (LIGHT BEAM SECTION PROPERTIES)

I have an existing structure built in 1970 and the structural drawing calls out a 18B40 beam section. My AISC Steel Manual 6th Edition does not have the beam section listed under the "light beam" section and neither does the WF section. I was not able to find it in the AISC Historic Shapes database either. When comparing other shapes it appears as if the section properties of a W18x40 would be similar.

Does anyone know where I can find information on a 18B40 beam section?

Thanks,
Katy

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