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Designing Steel Beams For Column Collapse

Designing Steel Beams For Column Collapse

Designing Steel Beams For Column Collapse

(OP)
I have 4 beams framing into a column. I need to design these beams for the potential collapse of the column. I am going to design a moment connection to transfer the moment after column collapse.

Does the beam have to be designed for the moment across the total length of the new span? The old spans were 30' each. The new span would be 60 ft. Is the moment connection designed for the moment of the 60 ft span plus the point loads from the other side?


Thank you.

RE: Designing Steel Beams For Column Collapse

Quote (OP)

Does the beam have to be designed for the moment across the total length of the new span?

Yes, it sounds that way.

Quote (OP)

Is the moment connection designed for the moment of the 60 ft span plus the point loads from the other side?

Yes, unless you can moment splice the beams going the other way as well and have the two lines of beams share load as a grillage.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Designing Steel Beams For Column Collapse

KootK has it. I think it would be more sensible to design for the moment in both directions.

RE: Designing Steel Beams For Column Collapse

(OP)
Great, thank you.

RE: Designing Steel Beams For Column Collapse

Haven't designed one of these yet, but isn't this a progressive collapse issue? I thought the philosophy was to allow the beams to go into flexural failure, but prevent sudden collapse. In this case, the connection must be detailed to transfer the full moment, shear and probably some catenary tension so that any plastic hinging occurs in the rolled sections and not the connection itself. Failure of the column allows the beam to drop and bend but catch itself in catenary action after significant deflection.

RE: Designing Steel Beams For Column Collapse

Yes, this sounds like a progressive collapse scenario. The beams will have to be designed for the new overall span length without the column there, but you can use full plastic moment capacity of the beam, typically disregard deflection limits (unless they get so large that it is a threat to life) and use load combinations specifically for extreme load cases (which vary depending on which criteria you use).

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