For a given loading the deflections of an indeterminate structures are generally _______ than those of its statically determinate structure counterpart
- Amore
- Bsimilar
- CsmallerCorrect
- Dnone of the above
Solution
Concept
Extra supports and restraints make indeterminate structures stiffer, so they deflect less.
Step-by-step solution
1. Indeterminate structures have extra (redundant) restraints. 2. Redundants increase the stiffness of the structure. 3. Higher stiffness means smaller deflection for the same load. 4. So the answer is smaller.
Explanation
Indeterminate structures have extra supports or members, so they are stiffer. For the same load, they deflect less than a similar determinate structure. For example, a fixed beam deflects much less than a simply supported beam.
Why the other options are wrong
A: More deflection is wrong, because indeterminate structures are stiffer. B: The deflections are not similar. They are clearly less. D: Option C is correct.
Shortcut
Fixed beam deflection (wL4/384EI) is 1/5 of simply supported beam deflection (5wL4/384EI).
Common mistake
Mixing up the disadvantages (temperature and settlement stresses) with deflection.
Correct answer: C) smaller