For a continuous beam, explain how a fixed-end moment due to a uniformly distributed load is distributed into adjacent spans when one of the supports settles significantly.

For a continuous beam, a uniformly distributed load (UDL) on a span initially creates fixed-end moments at the ends of that span. A fixed-end moment is the moment that would develop at the ends of a beam span if its ends were rigidly held against rotation. For a UDL 'w' over a span length 'L', this initial fixed-end moment at each end is wL²/12. These are the moments if the beam joints were entirely restrained from rotating. However, continuous beams have interior supports, known as joints, that can rotate.