The moment distribution method in structural analysis can be treated as
- AForce method
- BDisplacement methodCorrect
- CFlexibility method
- DNone of the above
Solution
Concept
Classification of moment distribution method
Formula
NONE
Step-by-step solution
1. The moment distribution method locks joint displacements to compute fixed-end moments. 2. Joints are then successively unlocked to distribute unbalanced moments based on rotational stiffness. 3. Because joint rotations (displacements) serve as the primary variables in solving the structure, it is a displacement method. Answer: B
Explanation
The moment distribution method determines internal bending moments by fixing joints against rotation and then systematically relaxing them to achieve equilibrium. Because joint displacements and rotations serve as the primary unknowns in the analysis, it is classified as a stiffness or displacement approach. Consequently, moment distribution is treated as a displacement method.
Why the other options are wrong
A) Force methods treat unknown forces or moments as primary variables, whereas moment distribution solves for joint rotations. C) Flexibility methods are force-based methods, unlike the displacement-based moment distribution method. D) Option B is correct as moment distribution is a displacement method.
Shortcut
Moment Distribution Method = Displacement (Stiffness) method.
Common mistake
Misclassifying the moment distribution method as a force method instead of a displacement method.
Correct answer: B) Displacement method