Helpful in establishing the shape of the M -diagram. The moment diagram closes out to zero at both ends. Be able to use sign of the moment to determine which portion of the beam is in tension and which is in compression. Positive Moment . . . Upper fibers are in compression.
Lower fibers are in tension.
Negative Moment . . . Upper fibers are in tension. Lower fibers are in compression. If diagram is linear at the crossing . . . Be able to use slope of diagram.