CO Structural Steel Contractor Exam
Questions And Correct Answers
(Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. Which of the following is the primary purpose of structural steel in
construction?
A. Decoration
B. Insulation
C. Load-bearing and structural support
D. Waterproofing
Rationale: Structural steel is primarily used for its high strength-to-
weight ratio to support loads in buildings and structures.
2. What is the typical carbon content in mild steel used for structural
purposes?
A. 0.01–0.05%
B. 0.15–0.25%
C. 0.50–0.70%
D. 1–2%
Rationale: Mild steel used in structural applications generally has a
low carbon content to maintain ductility and weldability.
3. The main advantage of using steel over concrete in certain structures is:
A. Fire resistance
B. High strength-to-weight ratio
C. Low cost
D. Low maintenance
Rationale: Steel is stronger relative to its weight, which allows for
longer spans and lighter structural elements.
4. Which of the following is a common method of connecting structural
steel members?
A. Glue
, B. Nails
C. Bolts and welds
D. Screws
Rationale: Steel members are typically joined using mechanical
fasteners like bolts or by welding.
5. Which steel section is most suitable for beams resisting bending?
A. Angle
B. I-beam
C. Plate
D. Channel
Rationale: I-beams have a high moment of inertia, which makes
them efficient at resisting bending loads.
6. What is the purpose of galvanizing structural steel?
A. Strengthen it
B. Prevent corrosion
C. Reduce weight
D. Improve flexibility
Rationale: Galvanizing applies a protective zinc coating to prevent
rust and corrosion.
7. What does ASTM A36 specify?
A. Aluminum alloys
B. Reinforced concrete
C. Carbon structural steel
D. Stainless steel
Rationale: ASTM A36 is a standard specification for carbon
structural steel commonly used in construction.
8. Which of the following tests determines the yield strength of steel?
A. Hardness test
B. Impact test
C. Tensile test
D. Bend test
Rationale: Tensile testing provides key properties such as yield
strength, ultimate strength, and elongation.
9. What is the typical minimum thickness of structural steel plates used in
heavy construction?
A. 1 mm
B. 3 mm
, C. 5 mm
D. 6 mm
Rationale: Structural steel plates for heavy construction usually start
at around 6 mm to ensure adequate strength.
10. Which of the following is a common defect in structural steel?
A. Dents
B. Cracks
C. Slag inclusions
D. Paint bubbles
Rationale: Slag inclusions are impurities trapped in the steel during
production and can weaken it.
11. The term “fabrication” in structural steel refers to:
A. Painting
B. Cutting, shaping, and assembling steel members
C. Transporting steel
D. Inspecting steel
Rationale: Fabrication involves preparing steel members through
cutting, bending, and assembly.
12. Which welding process is commonly used in structural steel
construction?
A. Gas welding
B. Shielded Metal Arc Welding (SMAW)
C. Laser welding
D. Resistance spot welding
Rationale: SMAW is widely used for site welding due to portability
and versatility.
13. Which factor primarily affects the load-carrying capacity of a
steel column?
A. Color of paint
B. Slenderness ratio
C. Length of bolts
D. Welding technique
Rationale: The slenderness ratio (column length vs. cross-section)
determines the risk of buckling under compressive loads.
14. When designing a steel beam for bending, which property is most
critical?
A. Yield strength
Questions And Correct Answers
(Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. Which of the following is the primary purpose of structural steel in
construction?
A. Decoration
B. Insulation
C. Load-bearing and structural support
D. Waterproofing
Rationale: Structural steel is primarily used for its high strength-to-
weight ratio to support loads in buildings and structures.
2. What is the typical carbon content in mild steel used for structural
purposes?
A. 0.01–0.05%
B. 0.15–0.25%
C. 0.50–0.70%
D. 1–2%
Rationale: Mild steel used in structural applications generally has a
low carbon content to maintain ductility and weldability.
3. The main advantage of using steel over concrete in certain structures is:
A. Fire resistance
B. High strength-to-weight ratio
C. Low cost
D. Low maintenance
Rationale: Steel is stronger relative to its weight, which allows for
longer spans and lighter structural elements.
4. Which of the following is a common method of connecting structural
steel members?
A. Glue
, B. Nails
C. Bolts and welds
D. Screws
Rationale: Steel members are typically joined using mechanical
fasteners like bolts or by welding.
5. Which steel section is most suitable for beams resisting bending?
A. Angle
B. I-beam
C. Plate
D. Channel
Rationale: I-beams have a high moment of inertia, which makes
them efficient at resisting bending loads.
6. What is the purpose of galvanizing structural steel?
A. Strengthen it
B. Prevent corrosion
C. Reduce weight
D. Improve flexibility
Rationale: Galvanizing applies a protective zinc coating to prevent
rust and corrosion.
7. What does ASTM A36 specify?
A. Aluminum alloys
B. Reinforced concrete
C. Carbon structural steel
D. Stainless steel
Rationale: ASTM A36 is a standard specification for carbon
structural steel commonly used in construction.
8. Which of the following tests determines the yield strength of steel?
A. Hardness test
B. Impact test
C. Tensile test
D. Bend test
Rationale: Tensile testing provides key properties such as yield
strength, ultimate strength, and elongation.
9. What is the typical minimum thickness of structural steel plates used in
heavy construction?
A. 1 mm
B. 3 mm
, C. 5 mm
D. 6 mm
Rationale: Structural steel plates for heavy construction usually start
at around 6 mm to ensure adequate strength.
10. Which of the following is a common defect in structural steel?
A. Dents
B. Cracks
C. Slag inclusions
D. Paint bubbles
Rationale: Slag inclusions are impurities trapped in the steel during
production and can weaken it.
11. The term “fabrication” in structural steel refers to:
A. Painting
B. Cutting, shaping, and assembling steel members
C. Transporting steel
D. Inspecting steel
Rationale: Fabrication involves preparing steel members through
cutting, bending, and assembly.
12. Which welding process is commonly used in structural steel
construction?
A. Gas welding
B. Shielded Metal Arc Welding (SMAW)
C. Laser welding
D. Resistance spot welding
Rationale: SMAW is widely used for site welding due to portability
and versatility.
13. Which factor primarily affects the load-carrying capacity of a
steel column?
A. Color of paint
B. Slenderness ratio
C. Length of bolts
D. Welding technique
Rationale: The slenderness ratio (column length vs. cross-section)
determines the risk of buckling under compressive loads.
14. When designing a steel beam for bending, which property is most
critical?
A. Yield strength
