Which of the following are the statically indeterminate beams?
- AFixed Beams
- BContinuous beams
- CBoth (A) and (B)Correct
- DNone of the above
Solution
Concept
Identification of statically indeterminate beams
Formula
NONE
Step-by-step solution
1. A structure is statically indeterminate if static equilibrium equations alone are insufficient to determine all reaction forces and internal stresses. 2. Fixed beams have fixed end moments that cannot be determined by static equilibrium equations alone. 3. Continuous beams have more support reactions than available equilibrium equations, making both fixed and continuous beams statically indeterminate. Answer: C
Explanation
A beam is statically indeterminate when the number of unknown support reactions exceeds the available static equilibrium equations. Both fixed beams and continuous beams have extra restraints that prevent free movement and cannot be analyzed using equilibrium equations alone. Thus, both beam types belong to the category of statically indeterminate structures.
Why the other options are wrong
A) Fixed beams are statically indeterminate, but continuous beams are also statically indeterminate. B) Continuous beams are statically indeterminate, but fixed beams are also statically indeterminate. D) Option C is correct as both fixed and continuous beams are statically indeterminate.
Shortcut
Fixed and Continuous beams both have redundant supports, making them statically indeterminate.
Common mistake
Selecting only fixed beams or continuous beams individually without realizing both structural types are statically indeterminate.
Correct answer: C) Both (A) and (B)