Distribution Factors:

As the supports A and D are fixed, the distribution factor in the members AB and DC are both zero, (DF)_AB = (DF)_DC = 0.

At joint B, the relative stiffnesses of the members are

K_BA =I/6 and K_BC =2I/6 =I/3

∴ (DF )_BA = (I/6)/(I/6)+(I/3) = 1/3 and (DF)_BC =2/3

At joint C, the relative stiffnesses of members are

K_CB = 2I/6 =I/3 and K_CD = I/3

(DF)_CB = (I/3)/(I/3)+(I/3) =1/2 and (DF)_CD =1/2

The moment distribution with the above assumed moments are given in the table below :

where K is an unknown multiplying factor.