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Designing a Steel Moment Frame

Designing a Steel Moment Frame

Designing a Steel Moment Frame

I have been working on designing multiple steel moment frame and I am not sure if I have been sizing them properly. I have multiple 2 story steel frames that will have full penetration welds on each beam to column connection. The foundation of the frames have a grade beam underneath to help resist the moment at the base of the frame.

Another concern I have is that one of the frames has a beam that cantilevers from the column and I do not know if a full penetration weld would be enough to properly resist the moment at that end.

Attached is an elevation of the one frame of great concern I have. I have been trying to use Risa 3D to help with the design but the suggested shapes it gives me seem incorrect, so I am assuming I am inputting something incorrectly.

RE: Designing a Steel Moment Frame

I reviewed both attachments, and you are basically on the right track (so don't call yourself "IAmNotVerySmart"wink

Some suggestions:
* At the Second Floor, I would cantilever the beam over the First Floor column, and not try to weld on a cantilever
* In your hand calcs, when you are calculating deflection, you did not consider the fact that the columns bend in double curvature--so the height to use in the equation would be half of the story height, not the full story height (for example, 4.5' at the Second story)
* I recommend H/300 to H/500 for allowable story drift, not H/240
* For the lower story, the shear is cumulative--so the shear in each lower story column is 7 kips, not 5 kips


RE: Designing a Steel Moment Frame

As Dave notes... I'd carry the beams over the columns and I'd use bolted connections for most of the stuff... I try to avoid CJPs and generally only for shop work... as for deflection, I'd use L/480 so L/500 is about right... same comment for shear. Using a modified portal approach the H/2 is correct as Dave notes.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?


RE: Designing a Steel Moment Frame

Thank you both for the inputs, I really appreciate it since it is difficult for me to find a lot of information online.

I will definitely adjust the deflection consideration but as for the cumulative shear in the stories I do consider that somewhere else in my calculations. I attached an example of how I perform lateral analysis in certain grid lines for a given project.

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