Plastic Collapse of a Sway Frame - IStructE Certificate in Structural Behaviour Course

Question from IStructE's Structural Behaviour Course, as part of the Certificate in Structural Behaviour.
This question asks you to calculate the minimum plastic moment resistance of a sway frame to resist the given collapse mechanism.
Recorded by Tim Lai, founder of The Structural Exam.
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Thumbnail image from the Structural Behaviour Course

[@avin636]

Wow.. This is good..Thank you very much.. 👌

[@TheLuminousOne]

What a legend.

[@BloodyXmass]

Thanks. Are you guys planning to make a video about plastic moments on a continuous beam? It is one example as well and I cannot figure out how to get the correct answer.

[@TheStructuralExam]

Yes! Was looking through these questions just a couple of days ago. I have a couple of other topics first, but conceptually it's not really any different to frames though.

[@sarwarn2107]

Don't you think you need to break down the frame into 2 mechanisms rather than combining? The first mechanism plastic moment is 80kNm and the other one from the 100kN load will cause the collapse which is 50kNm.

[@waveisocean]

Hello, can you please explain why there are 6 thetas rather than 7?

[@refnaldinho9717]

because u only add the theta where hinges are formed, ~ so for the four hinges = theta + 2theta + 2theta + theta