Designation of W-Sections

[StructuralAddict]

The designations of a W-Section is chosen such that the first number represents its approximate depth and the second number represents its unit weight.

My question is: why there are many deviations from this rule?
For example, W36x652 section has a depth of 41.1". So, why wasn't it grouped with the W40 family? Note that the depth of the sections in the W40 family ranges from 38.2" to 43.0".

Thank you!

 

[XR250]

I believe that the nominal depth class it based more on the flange to flange distance measured from inside to inside rather than outside to outside.

 

[hokie66]

XR250 is correct. They are bunched in accordance with the rolling mill dimensions. The outside dimensions just depend on how much steel is used for each section.

 

[Earth314159]

The nominal designation is based on the rollers used to make the section. A big chunk of steel is repeatedly moved through rollers that shape the steel into a section. The inside dimensions of the section are set by one set of rollers. The outer rollers are moved out to increase the flange depth.

 

[CANPRO]

If you're thrown off by the variation in the W40's, wait until you realize that a W14x730 is over 22" deep.

 

[dold]

Youll notice that all the T dimensions are, with a few exceptions, the same for each depth class. And as others have pointed out this has to do with the rolling process.

 

[JoelTXCive]

I thought they did it just to make our lives interesting.

The standard, X-strong, and XX-strong pipes, are other items where the names do not match up with well with the inside or outside dimensions sometimes.

 

[RWW0002]

Interesting post a while back on Pipe sizes..

https://www.eng-tips.com/viewthread.cfm?qid=336095

Once again, although more arbitrary than W shapes, there is a reason behind the madness.