In the moment distribution method, what governs the distribution of moments at joints?

• A. Wind load factors.
• B. Soil bearing capacity factors.
• C. Stiffness-based distribution factors.
• D. Temperature coefficients.

Answer: (C)

The way moments are shared at a joint in the moment distribution method is governed by the rotational stiffness of each connected member. Each member resists rotation about the joint with a stiffness that depends on its EI and length, and on how the far end is restrained. The moments are distributed to the connected members in proportion to their stiffness (the distribution factors), so a stiffer member takes more of the unbalanced moment. Wind or loads set the initial fixed-end moments, but the actual distribution among members relies on stiffness-based distribution factors, not soil bearing, wind factors, or temperature coefficients.