Which of the following structural elements is most efficient in resisting axial compressive loads?
- AI-beam
- BCircular hollow sectionCorrect
- CRectangular solid section
- DT-section
Solution
Concept
Efficiency of sections under compressive loads
Formula
NONE
Step-by-step solution
1. Structural efficiency under axial compression depends on the cross-section's radius of gyration and resistance to buckling. 2. Buckling resistance is maximized when cross-sectional material is optimally distributed about the principal axes. Answer: B
Explanation
A circular hollow section has a uniform radius of gyration in all directions, giving it equal resistance to buckling along any axis. This symmetric distribution of material away from the central axis maximizes structural efficiency under axial compression. Therefore, option B correctly identifies the most efficient section for compression members.
Why the other options are wrong
A) I-beams are designed primarily to resist bending moments rather than pure axial compression. C) Solid rectangular sections have lower material efficiency in compression compared to the specified section.
Shortcut
Circular Hollow Section (CHS) has equal radius of gyration in all directions, making it most efficient against buckling.
Common mistake
Selecting option A (I-beam) by assuming its high efficiency in resisting bending moments also applies to pure axial compression.
Correct answer: B) Circular hollow section