For a skeletal frame shown in the figure Static and kinematic in
For a skeletal frame shown in the figure
Static and kinematic indeterminacies are
A. 9 and 11
B. 3 and 9
C. 3 and 6
D. 6 and 3
Please scroll down to see the correct answer and solution guide.
Right Answer is: A
SOLUTION
Concept:
Static Indeterminacy: If the equilibrium equations are enough to analyze for unknown reactions, the structure is said to be statically indeterminate.
Ds = Dse + Dsi
Dse = r – S
Dsi = 3 × Number of closed loop (For portal frame)
Dsi = m- 2j+ 3 (For truss structure)
Kinematic Indeterminacy: It is the total number of possible degree of freedom of all the joints.
Dk = 3J - r (For beam & portal frame)
Dk = 2J-r (For truss structure)
where, Dse = External Indeterminacy, Dsi = Internal Indeterminacy, Dk = Kinematic Indeterminacy, r = No. of unknown reactions, S = No. of equilibrium equation, m = No. of mombers & J = No. of joints
Solution:
Static Indeterminacy,
Dse = r – S = 6 - 3 = 3
Dsi = 3 × 2 = 6
Ds = 6 + 3 = 9
Kinematic Indeterminacy,
Dk = 3J - r = 3 × 9 – 6 = 21
Dk = 21 - 10 = 11 (For rigid members)