Carry over Moments:
As soon as we distribute the balancing moment M to each member as in Eq. a fixing moment equal to half its value appears at the other end of the member. For example, if we distribute a moment M B′ A = M (Ki/∑ K) to end B of member BA, a moment ( =MB′A/2) appears at the other end A of the member which is fixed. Refer Eq. (3.8). This happens to all the other members DB, CB and EB which meet at B. These moments are called carry over moments.
Now, if the structure is not a simple joint as shown in but forms part of an extended structure which may extend beyond the joints A, D, C, E, etc. then these carry over moments produce an unbalanced condition at all these remote ends. This needs a second cycle of adjustments or moment distribution, with the next round of carry over and so on. The cycle is frequent.
But as begin above, the distribution moments get smaller in value each time and the moment distribution process converges fast enough as we shall soon see.