Question

A beam is a structural member which is subjected to

• A. Axial tension or compression
• B. Transverse loads and couples
• C. Twisting moment
• D. No load, but its axis should be horizontal and x-section rectangular or circular

Hint:

Remember: Beams resist bending due to transverse loads, columns resist axial loads, and shafts resist torsion.

Answer 1

The Correct Option is B

Structural members are classified by the type of internal force they are designed to resist: columns resist axial force, shafts resist torque, and beams resist transverse loading through bending.

1. Axial tension/compression: Characteristic of columns and ties, not beams.
2. Transverse loads and couples: Characteristic of beams, loads perpendicular to the member's axis, causing bending.
3. Twisting moment: Characteristic of shafts, not beams.
4. No load with fixed geometry: Not a loading condition at all, so it can't define a structural member's function.

Answer 2

Consider the internal stress resultants that actually develop inside each type of member under its typical service loading, since this is the most direct way to identify what type of member is being described.

1. Axial tension or compression: Produces a uniform normal stress across the cross-section with no bending, characteristic of a column or tie rod, not a beam.
2. Transverse loads and couples: Produces varying bending moment and shear force along the member's length, with bending stresses that vary across the depth of the cross-section, the hallmark internal stress state of a beam.
3. Twisting moment: Produces shear stress from torsion, distributed radially about the member's axis, characteristic of a shaft.
4. No load: Produces no internal stress resultants at all, so it cannot be used to classify the member's structural role.

Therefore, the correct answer is transverse loads and couples.