Question

Which of the following statements is/are correct in the context of steel construction?

• A. Weathered steel forms a rust-like layer when exposed to weathering.
• B. Intumescent paints on steel sections improve passive fire protection.
• C. For the same weight, steel I-beam has more flexure-bearing capacity in comparison to Castellated steel beam.
• D. Outrigger systems provide additional torsional rigidity against lateral loads in tall structures.

Hint:

Check each claim: weathering steel's patina and intumescent coatings are both real, but a castellated beam, not a plain I-beam, has the greater flexural capacity for the same weight.

Answer 1

The Correct Option is A, B, D

Step 1: Check option (A), weathering steel.
Weathering steel (commonly called Cor-Ten steel) is a low-alloy steel that is deliberately allowed to rust in a controlled way. The initial corrosion forms a dense, tightly adhering oxide patina that looks rust-like on the surface but actually seals the steel underneath and slows further corrosion. This statement is correct.

Step 2: Check option (B), intumescent paint.
Intumescent paint is a thin coating applied to structural steel that stays inert at normal temperature. When a fire raises the steel's temperature, the coating swells up into a thick, low-conductivity char layer that insulates the steel and slows its temperature rise, buying more time before the steel loses strength. This is a standard passive fire protection method for exposed steel members, so the statement is correct.

Step 3: Check option (C), I-beam versus Castellated beam.
A castellated beam is made by cutting a rolled I-section along a zig-zag line and rewelding the two halves so the overall depth increases while the steel weight stays almost the same. Because bending capacity depends strongly on section depth, the deeper castellated section carries more bending moment for the same weight of steel than the original, shallower I-beam. So the claim that the plain I-beam has more flexural capacity than the castellated beam, for equal weight, is the reverse of the truth. This statement is incorrect.

Step 4: Check option (D), outrigger systems.
In a tall building, an outrigger is a stiff horizontal member, often a truss or wall, that connects the central core to the outer perimeter columns at one or more levels. Under lateral load from wind or seismic action, the core alone would rotate and sway; the outrigger forces the perimeter columns to share this rotation by going into extra tension and compression, which adds torsional and overturning rigidity to the whole structure and cuts down lateral drift. This statement is correct.

Final Answer:
Statements (A), (B) and (D) are correct, while (C) is false, since a castellated beam actually out-performs an equal-weight plain I-beam in bending capacity.
\[ \boxed{\text{(A), (B), (D)}} \]