Rolled steel beams – primary function: In structural steelwork, what are rolled steel beams mainly used for?

Introduction / Context:
Rolled steel beams (I-beams and H-beams) are the backbone of floor and roof systems. Their flanges and web geometry are optimized to resist bending and shear from distributed and concentrated loads. Understanding their primary role clarifies correct selection and detailing in frames and composite construction.

Given Data / Assumptions:

• Standard rolled beams with two flanges and a web.
• Members used primarily in flexure (beams and girders).
• Not considering columns (axial compression) or pure ties (axial tension) as the primary role.

Concept / Approach:

Beams are flexural members. Their section modulus and moment of inertia are tailored to resist bending moments with economical steel usage: material is concentrated at the flanges where bending stresses are highest. The web carries shear. While beams can also experience some axial force in frames, they are not selected primarily as independent tension or compression elements.

Step-by-Step Solution:

Verification / Alternative check:

Design checks per steel codes emphasize bending strength, lateral torsional buckling, and shear in the web, confirming the flexural role.

Why Other Options Are Wrong:

• Independent compression: that is a column’s role; beams are not optimized for pure axial compression.
• Independent tension: tension members are better as flats, angles, rods, or cables.
• “All the above” is too broad and misleading.

Common Pitfalls:

• Ignoring lateral bracing requirements against lateral torsional buckling.
• Overlooking shear buckling checks in slender webs.

Final Answer:

Mainly used to resist bending stress.