The three moment equation in structural analysis is basically a
- AStiffness method
- BDisplacement method
- CEnergy method
- DFlexibility methodCorrect
Solution
Concept
Classification of three moment equation
Formula
NONE
Step-by-step solution
1. Clapeyron's three moment equation relates bending moments at three consecutive supports of continuous beams. 2. Primary redundant unknowns chosen in this method are internal support moments rather than joint displacements. 3. Structural methods that treat force or moment quantities as primary unknowns are flexibility methods. Answer: D
Explanation
Clapeyron's three-moment equation solves continuous beams by formulating equations in terms of unknown support bending moments. Because redundant moments are treated as the primary unknown forces to satisfy slope continuity, it belongs to the force method category. Therefore, the three-moment equation is fundamentally a flexibility method.
Why the other options are wrong
A) Stiffness methods solve for unknown joint displacements rather than redundant moments. B) Displacement methods treat member end displacements as the primary unknowns. C) Energy methods rely on strain energy principles rather than direct compatibility of support moments.
Shortcut
Three-moment equation (Clapeyron's) = Flexibility (Force) method.
Common mistake
Classifying the three-moment equation as a displacement or stiffness method instead of a flexibility method.
Correct answer: D) Flexibility method