Axial Force is defined as which of the following?

• A. A bending moment about the member
• B. A force along the length of the member
• C. A force perpendicular to the member
• D. A force due to wind

Answer: (B)

Axial force is the force that runs along the length of a structural member, producing tension or compression along its axis. When a load is aligned with the member, the internal force acts through the cross-section parallel to the member's length, causing normal stress (N/A) without inherently causing bending or shear. This is different from a bending moment, which is the rotational effect that tends to bend the member and is not a force along its length. A force perpendicular to the member is a transverse load that tends to cause shear and bending rather than axial load. Wind is an external load that can act in many directions; it isn’t defined as axial unless a component of the wind load acts along the member’s length. In short, axial force is the in-line force along the member’s axis, such as tension or compression.