Questions and discussion for this lecture live here. Fire away by hitting Reply below 
Hey Sean.
I was wondering how it’ll be possible to calculate the Design moment for a continuous beam
Hey,
When you say Design Moment, I assume you mean the moment that arises due to the externally applied loads (rather than the moment of resistance). For statically indeterminate structures there are various techniques; a simple one you can implement by hand is the moment distribution method, I cover it here.
Hi Sean,
At around 2:33 you say that we should assume that the steel fails before the concrete crushes and this allows us to equate 0.567fck(0.8xb) to 0.87fykAs. But doesn’t this equation mean that we are assuming the concrete crushes and the steel fails simultaneously? What am I missing here? Thanks!
Hey @jeremy.mangion.11 - apologies for the delay in replying - we has a technical hiccup here so I wasn’t receiving question notifications for the last couple of weeks!! All sorted again so working through the backlog now.
To your question; you are not missing anything. This equation is indeed equating the force in the concrete compression block at failure with the force in the steel at failure - i.e. implying simultaneous failure. We do this to identify the limit on compression block depth so that we can ensure that the it never gets to the point that both steel and concrete fail at the same time and that it’s always the steel that yields first.
Seán