old style open web beam analysis

[elance300]

Hello,

I am doing an analysis of an existing building and need to determine the capacity of an open web beam created by cutting a w-shape lengthwise and splicing two halves back together ( see pic )

Can anyone help me determine the analysis method for these types of beams? Need to place new mech equipment on the floor above and check the floor capacity.

Also, the beam is called out as "18/12 open-web beam." Not sure what is meant by the 18/12.

Thanks

 

[woodman88]

If you search the web for "Castellated Beams – New Developments" you can download the paper Castellated Beams—New Developments by J. P. BOYER. This paper was presented at the AISC National Engineering Conference, Omaha, Nebr., in May, 1964.
I would guess that the 18/12 means a 12" beam is cut so that a 18" castellated beam could be made from it.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[hokie66]

Castellated beams were common in the 1960's and 70's, and I designed a number of them, mostly for roof spans in the order of 100'. As I remember, we used Omer Blodgett's method in "Design of Welded Structures". The following thread gives other references.

thread507-15392

Just looking at the elevation of your beam, I think the end panels would be the most critical, as the top and bottom "chords" are only 3" deep at that point. You may find that for substantial additional load, filling in the hexagons at the ends would help. I remember that we typically used a longer solid web section near the end.

 

[jimstructures]

Design of Welded Structures by Omer Blodgett published by James F. Lincoln Arc Welding Foundation in Cleveland, OH has an entire chapter (4.7) on this type of beam.

New Millennium the steel joist and steel deck suppliers have material on expanded beams although theirs are shapped a little differently.

Jim

 

[elance300]

thanks to all - I didn't know they were also called castellated beam. That makes a big difference when trying to google for information.

 

[SethGuthrie]

You could check the design using RAM SBeam, (current codes). There is even a free version form CSC.

http://www.cmc.com/en/americas/cmcsteelproducts/Pages/designprogram.aspx

 

[paddingtongreen]

Sometimes, when shear was a problem, the holes at the ends had shaped plates welded into them.

Michael.
Timing has a lot to do with the outcome of a rain dance.