Questions and discussion for this lecture live here. Fire away by hitting Reply below 
Hi, looking at 3min 30 sec in: shouldn’t we be looking for KCB, not KBC? We don’t have a definition for this stiffness condition ‘continuous with pinned end’ or are they interchangeable?
Thank you
Hi,
For stiffness, we’re calculating one number for each member and the stiffness is determined based on the conditions at the end of the member (assuming EI is constant throughout the structure).
So, we could refer to the stiffness of member BC as K_BC or K_CB - the subscript order is not significant…only a label in this case.
Where the subscript is more significant is when it comes to labelling the distribution factors. The DF that indicates the moment distributed into member AB (or member BA…again, just a label) is indicated as DF_BA, i.e. the moment distributed form joint B into member AB. Similarly, for member BC, the distribution factor would be DF_BC, i.e. from joint B into member BC.
If any of this is still confusing - please follow up with another question.
S