Question

In the case of stiffness method of structural analysis, the quantity taken as redundant is

• A. Deflection or rotation
• B. Torsion
• C. Bending
• D. Strain energy

Hint:

Matrix methods: \[ \boxed{ \begin{aligned} \text{Force Method} &\rightarrow \text{Unknowns are Forces}\\ \text{Stiffness Method} &\rightarrow \text{Unknowns are Displacements} \end{aligned} } \]

Answer 1

The Correct Option is A

Step 1: Contrast the two classical methods.
The force (flexibility) method treats redundant forces as the unknowns, while the stiffness (displacement) method works the other way round.
Step 2: Identify what is unknown in the stiffness method.
Here we first assume the joint displacements, that is deflections and rotations, are unknown, write equilibrium in terms of them using member stiffness, and solve for these displacements directly.
Step 3: Name the redundant quantity.
Since the unknowns being solved for are displacements, the redundant quantity in the stiffness method is deflection or rotation.
\[ \boxed{\text{Deflection or rotation}} \]