Composite Construction – Provisions for Cased Columns Which statements correctly describe standard provisions for steel sections encased in reinforced concrete (cased columns)?

Introduction / Context:
Cased columns combine a structural steel core with reinforced concrete encasement to enhance fire resistance, stiffness, and durability. Proper detailing ensures composite action and corrosion protection while maintaining constructability on site.

Given Data / Assumptions:

• Steel core: rolled I-section or channels back-to-back, optionally with flange plates.
• Concrete encasement: dense concrete with suitable aggregate size and target strength.
• Cover and dimensional limits: minimum covers and overall size caps for practical site work.

Concept / Approach:

Encasement improves fire rating and protects the steel against corrosion while allowing the composite section to share load. Minimum cover and concrete quality ensure durability and adequate confinement, and dimensional limits keep transportation and shuttering practical.

Step-by-Step Solution:

Verification / Alternative check:

Composite design guides and standard detailing manuals present similar practical detailing rules that align with the above statements.

Why Other Options Are Wrong:

• Options a–d each reflect correct aspects; none are individually incorrect, therefore the combined correct choice is “All the above”.

Common Pitfalls:

Painting the steel before encasement (may impair bond), inadequate cover in aggressive exposure, or oversize steel cores that complicate reinforcement placement and concrete compaction.

Final Answer:

All the above