APSC Assistant Engineer - Design of Concrete Structures Questions
1. A simply supported beam of 5 m span carries a uniformly distributed load of 20 kN/m. What is the maximum bending moment in kNm?
b. 62.5
Description: For a simply supported beam, maximum bending moment M = wL²/8, where w = 20 kN/m, L = 5 m. M = (20 × 5²)/8 = 62.5 kNm, critical for beam design.
Description: For a simply supported beam, maximum bending moment M = wL²/8, where w = 20 kN/m, L = 5 m. M = (20 × 5²)/8 = 62.5 kNm, critical for beam design.
2. Which statement is true about the limit state method?
b. It ensures safety and serviceability
Description: The limit state method (per IS 456) balances collapse and serviceability using partial safety factors, unlike working stress method.
Description: The limit state method (per IS 456) balances collapse and serviceability using partial safety factors, unlike working stress method.
3. A rectangular beam section is 300 mm wide and 500 mm deep (effective). If it carries a moment of 100 kNm, what is the required area of steel (in mm²) using M20 concrete and Fe415 steel?
b. 750
Description: Using Mu = 0.87fyAst(d - 0.42xu), for M20 (fck = 20 MPa), Fe415 (fy = 415 MPa), Mu,lim ≈ 132 kNm > 100 kNm, so singly reinforced. Solving: Ast ≈ 750 mm², ensuring moment resistance.
Description: Using Mu = 0.87fyAst(d - 0.42xu), for M20 (fck = 20 MPa), Fe415 (fy = 415 MPa), Mu,lim ≈ 132 kNm > 100 kNm, so singly reinforced. Solving: Ast ≈ 750 mm², ensuring moment resistance.
4. Which statement is correct about shear reinforcement?
b. It resists diagonal tension in beams
Description: Shear reinforcement (stirrups) counters diagonal cracks in beams due to shear forces, not compression or exclusive to columns.
Description: Shear reinforcement (stirrups) counters diagonal cracks in beams due to shear forces, not compression or exclusive to columns.
5. A square footing supports a column load of 1000 kN. If the safe bearing capacity of soil is 200 kN/m², what is the minimum side length of the footing in meters?
b. 2.2
Description: Area = Load ÷ SBC = 1000 ÷ 200 = 5 m². For a square footing, side = √5 ≈ 2.24 m, rounded to 2.2 m for safety.
Description: Area = Load ÷ SBC = 1000 ÷ 200 = 5 m². For a square footing, side = √5 ≈ 2.24 m, rounded to 2.2 m for safety.
6. Which statement is true about one-way slabs?
b. They are supported on two opposite sides
Description: One-way slabs span primarily in one direction, supported on two sides, requiring main reinforcement along the span, unlike two-way slabs.
Description: One-way slabs span primarily in one direction, supported on two sides, requiring main reinforcement along the span, unlike two-way slabs.
7. A short column of 300 mm × 400 mm carries an axial load of 800 kN. What is the stress in concrete (in N/mm²) using M20 concrete?
b. 6.0
Description: Stress = Load ÷ Area = 800 × 10³ ÷ (300 × 400) = 6.67 N/mm² ≈ 6.0 N/mm² (considering steel contribution negligible), safe for M20.
Description: Stress = Load ÷ Area = 800 × 10³ ÷ (300 × 400) = 6.67 N/mm² ≈ 6.0 N/mm² (considering steel contribution negligible), safe for M20.
8. Which statement is correct about development length?
b. It ensures full transfer of stress to concrete
Description: Development length anchors bars to transfer stress via bond, used in all members, and increases with steel grade (e.g., Fe415 vs. Fe500).
Description: Development length anchors bars to transfer stress via bond, used in all members, and increases with steel grade (e.g., Fe415 vs. Fe500).
9. A beam has a shear force of 100 kN at the support. If shear strength of concrete (τc) is 0.8 N/mm² for M20, and section is 300 mm × 500 mm (effective), what is the shear resisted by concrete in kN?
b. 100
Description: Shear resistance = τc × b × d = 0.8 × 300 × 500 × 10⁻³ = 120 kN > 100 kN, so concrete resists 100 kN without stirrups.
Description: Shear resistance = τc × b × d = 0.8 × 300 × 500 × 10⁻³ = 120 kN > 100 kN, so concrete resists 100 kN without stirrups.
10. Which statement is true about doubly reinforced beams?
b. They resist both tension and compression
Description: Doubly reinforced beams have steel in tension and compression zones, enhancing capacity, permitted by IS 456, and stronger than singly reinforced beams.
Description: Doubly reinforced beams have steel in tension and compression zones, enhancing capacity, permitted by IS 456, and stronger than singly reinforced beams.
11. A one-way slab has a span of 3 m and carries a live load of 3 kN/m². Using M20 concrete, what is the effective depth required (in mm)?
b. 120
Description: Total load ≈ 5.5 kN/m² (DL + LL), moment M = wL²/8. Using Mu = 0.138fckbd², d ≈ 120 mm satisfies deflection and strength for M20.
Description: Total load ≈ 5.5 kN/m² (DL + LL), moment M = wL²/8. Using Mu = 0.138fckbd², d ≈ 120 mm satisfies deflection and strength for M20.
12. Which statement is true about short columns?
b. They are designed for axial loads
Description: Short columns (slenderness < 12) resist axial loads with minimal buckling, requiring reinforcement per IS 456.
Description: Short columns (slenderness < 12) resist axial loads with minimal buckling, requiring reinforcement per IS 456.
13. A footing carries a load of 1200 kN and has an area of 4 m². What is the bearing pressure in kN/m²?
b. 300
Description: Bearing pressure = Load ÷ Area = 1200 ÷ 4 = 300 kN/m², which must be less than the soil’s safe bearing capacity.
Description: Bearing pressure = Load ÷ Area = 1200 ÷ 4 = 300 kN/m², which must be less than the soil’s safe bearing capacity.
14. Which statement is correct about deflection control?
b. It ensures serviceability of structures
Description: Deflection limits (e.g., L/250) in IS 456 prevent cracking and ensure usability, applicable to beams and slabs, not strength.
Description: Deflection limits (e.g., L/250) in IS 456 prevent cracking and ensure usability, applicable to beams and slabs, not strength.
15. A beam of 4 m span carries a point load of 40 kN at midspan. What is the maximum shear force in kN?
b. 20
Description: For a simply supported beam, shear force = P/2 = 40/2 = 20 kN at supports, critical for shear design.
Description: For a simply supported beam, shear force = P/2 = 40/2 = 20 kN at supports, critical for shear design.
16. Which statement is true about two-way slabs?
b. They are supported on all four sides
Description: Two-way slabs distribute loads in both directions, supported on all sides, requiring reinforcement in both directions, unlike beams.
Description: Two-way slabs distribute loads in both directions, supported on all sides, requiring reinforcement in both directions, unlike beams.
17. A column carries an axial load of 1500 kN. If M25 concrete is used, what is the minimum area of the column in mm²?
b. 250000
Description: Pu = 0.4fckAc + 0.67fyAsc (assume Asc = 0 for simplicity). For M25, Ac = 1500 × 10³ ÷ (0.4 × 25) = 250000 mm², minimum area.
Description: Pu = 0.4fckAc + 0.67fyAsc (assume Asc = 0 for simplicity). For M25, Ac = 1500 × 10³ ÷ (0.4 × 25) = 250000 mm², minimum area.
18. Which statement is true about bond stress?
b. It transfers load between steel and concrete
Description: Bond stress ensures steel and concrete act together, varies along bars, and increases with smaller diameters per IS 456.
Description: Bond stress ensures steel and concrete act together, varies along bars, and increases with smaller diameters per IS 456.
19. A slab has a thickness of 150 mm and carries a total load of 8 kN/m². What is the factored load in kN/m²?
b. 12
Description: Factored load = 1.5 × characteristic load = 1.5 × 8 = 12 kN/m², per IS 456 limit state design for safety.
Description: Factored load = 1.5 × characteristic load = 1.5 × 8 = 12 kN/m², per IS 456 limit state design for safety.
20. Which statement is correct about torsion reinforcement?
b. It resists twisting moments in beams
Description: Torsion reinforcement (stirrups and longitudinal bars) counters twisting, mainly in beams, essential per IS 456, not affecting axial capacity.
Description: Torsion reinforcement (stirrups and longitudinal bars) counters twisting, mainly in beams, essential per IS 456, not affecting axial capacity.
21. The primary purpose of reinforcement in concrete is to:
b. Resist tensile stresses
Description: Concrete is weak in tension, so steel reinforcement handles tensile forces, not compression, weight, or workability.
Description: Concrete is weak in tension, so steel reinforcement handles tensile forces, not compression, weight, or workability.
22. The minimum grade of concrete for RCC as per IS 456 is:
b. M20
Description: IS 456 mandates M20 for RCC to ensure adequate strength and durability; M10 is for plain concrete.
Description: IS 456 mandates M20 for RCC to ensure adequate strength and durability; M10 is for plain concrete.
23. The characteristic strength of concrete is defined at:
b. 28 days
Description: Concrete strength (fck) is measured at 28 days per IS 456, as it reaches most of its design strength then.
Description: Concrete strength (fck) is measured at 28 days per IS 456, as it reaches most of its design strength then.
24. The maximum spacing of stirrups in beams as per IS 456 is:
b. 300 mm
Description: IS 456 limits stirrup spacing to 0.75d or 300 mm (whichever is less) to ensure shear resistance and confinement.
Description: IS 456 limits stirrup spacing to 0.75d or 300 mm (whichever is less) to ensure shear resistance and confinement.
25. The primary purpose of a column footing is to:
b. Distribute load to soil
Description: Footings spread column loads to prevent soil failure, not for height, strength reduction, or aesthetics.
Description: Footings spread column loads to prevent soil failure, not for height, strength reduction, or aesthetics.
26. The partial safety factor for concrete in limit state design is:
b. 1.5
Description: IS 456 uses 1.5 for concrete to account for material variability, ensuring safety in design.
Description: IS 456 uses 1.5 for concrete to account for material variability, ensuring safety in design.
27. The minimum cover for a slab exposed to moderate environment is:
b. 20 mm
Description: IS 456 specifies 20 mm cover for slabs in moderate exposure to protect reinforcement from corrosion.
Description: IS 456 specifies 20 mm cover for slabs in moderate exposure to protect reinforcement from corrosion.
28. The primary purpose of distribution steel in slabs is to:
b. Control shrinkage cracks
Description: Distribution steel manages cracks due to shrinkage and temperature, while main steel resists bending.
Description: Distribution steel manages cracks due to shrinkage and temperature, while main steel resists bending.
29. The maximum strain in concrete at failure in limit state design is:
b. 0.0035
Description: IS 456 assumes concrete fails at a strain of 0.0035, defining the ultimate limit state for design.
Description: IS 456 assumes concrete fails at a strain of 0.0035, defining the ultimate limit state for design.
30. The primary purpose of a beam is to:
b. Support vertical loads
Description: Beams transfer loads (e.g., from slabs) to columns, not affecting slab thickness, column size, or footing depth.
Description: Beams transfer loads (e.g., from slabs) to columns, not affecting slab thickness, column size, or footing depth.
31. The minimum reinforcement in slabs as per IS 456 is:
b. 0.12%
Description: IS 456 mandates 0.12% reinforcement for Fe415 steel in slabs to control cracking and ensure ductility.
Description: IS 456 mandates 0.12% reinforcement for Fe415 steel in slabs to control cracking and ensure ductility.
32. The primary purpose of a tie in columns is to:
b. Prevent buckling of bars
Description: Ties confine longitudinal bars, preventing buckling under compression, per IS 456, not for aesthetics or strength reduction.
Description: Ties confine longitudinal bars, preventing buckling under compression, per IS 456, not for aesthetics or strength reduction.
33. The modular ratio for M20 concrete with Fe415 steel is approximately:
b. 13
Description: Modular ratio = Es/Ec ≈ 280/(3fck) per IS 456. For M20, m ≈ 13, used in working stress design.
Description: Modular ratio = Es/Ec ≈ 280/(3fck) per IS 456. For M20, m ≈ 13, used in working stress design.
34. The maximum diameter of bars in slabs as per IS 456 is:
b. 12 mm
Description: IS 456 limits slab bar diameter to 1/8 of thickness or typically 12 mm to ensure proper bonding and crack control.
Description: IS 456 limits slab bar diameter to 1/8 of thickness or typically 12 mm to ensure proper bonding and crack control.
35. The primary purpose of anchorage in reinforcement is to:
b. Ensure stress transfer
Description: Anchorage (e.g., hooks) ensures bars transfer stress to concrete, not affecting length, strength, or workability.
Description: Anchorage (e.g., hooks) ensures bars transfer stress to concrete, not affecting length, strength, or workability.
36. The minimum clear cover for columns as per IS 456 is:
b. 40 mm
Description: IS 456 specifies 40 mm cover for columns in moderate exposure to protect against corrosion and fire.
Description: IS 456 specifies 40 mm cover for columns in moderate exposure to protect against corrosion and fire.
37. The primary purpose of a lintel is to:
b. Span openings in walls
Description: Lintels carry loads above doors/windows, not for roofs, columns, or slabs.
Description: Lintels carry loads above doors/windows, not for roofs, columns, or slabs.
38. The maximum reinforcement ratio in beams as per IS 456 is:
b. 4%
Description: IS 456 limits tension reinforcement to 4% to prevent brittle failure and ensure ductility.
Description: IS 456 limits tension reinforcement to 4% to prevent brittle failure and ensure ductility.
39. The primary purpose of a cantilever beam is to:
b. Project beyond support
Description: Cantilever beams extend without support at one end, used for balconies, not for multiple spans or load reduction.
Description: Cantilever beams extend without support at one end, used for balconies, not for multiple spans or load reduction.
40. The partial safety factor for steel in limit state design is:
b. 1.15
Description: IS 456 uses 1.15 for steel to account for material uncertainties, lower than concrete’s 1.5 due to steel’s reliability.
Description: IS 456 uses 1.15 for steel to account for material uncertainties, lower than concrete’s 1.5 due to steel’s reliability.
41. The primary purpose of a raft foundation is to:
b. Distribute load over large area
Description: Raft foundations spread loads uniformly, ideal for weak soils, not for single columns or height reduction.
Description: Raft foundations spread loads uniformly, ideal for weak soils, not for single columns or height reduction.
42. The minimum number of longitudinal bars in a rectangular column is:
b. 4
Description: IS 456 requires at least 4 bars in rectangular columns for stability and load distribution.
Description: IS 456 requires at least 4 bars in rectangular columns for stability and load distribution.
43. The primary purpose of a water-cement ratio is to:
b. Control concrete strength
Description: Lower water-cement ratios increase strength and durability per IS 456, not affecting reinforcement or thickness.
Description: Lower water-cement ratios increase strength and durability per IS 456, not affecting reinforcement or thickness.
44. The maximum deflection limit for beams as per IS 456 is:
b. Span/250
Description: IS 456 limits beam deflection to span/250 to ensure serviceability and prevent damage to finishes.
Description: IS 456 limits beam deflection to span/250 to ensure serviceability and prevent damage to finishes.
45. The primary purpose of a strap footing is to:
b. Connect adjacent footings
Description: Strap footings link closely spaced footings to balance loads, not for single columns or slab thickness.
Description: Strap footings link closely spaced footings to balance loads, not for single columns or slab thickness.
46. The minimum grade of steel for RCC as per IS 456 is:
b. Fe415
Description: IS 456 recommends Fe415 for RCC due to its balance of strength and ductility; Fe250 is for mild steel.
Description: IS 456 recommends Fe415 for RCC due to its balance of strength and ductility; Fe250 is for mild steel.
47. The primary purpose of a dowel bar is to:
b. Transfer load between slabs
Description: Dowel bars ensure load sharing in concrete pavements, not affecting thickness, strength, or curing.
Description: Dowel bars ensure load sharing in concrete pavements, not affecting thickness, strength, or curing.
48. The maximum spacing of main bars in slabs as per IS 456 is:
b. 3d
Description: IS 456 limits main bar spacing to 3d or 300 mm to ensure uniform load distribution and crack control.
Description: IS 456 limits main bar spacing to 3d or 300 mm to ensure uniform load distribution and crack control.
49. The primary purpose of a retaining wall is to:
b. Resist lateral earth pressure
Description: Retaining walls counter soil pressure, not for roofs, foundations, or columns.
Description: Retaining walls counter soil pressure, not for roofs, foundations, or columns.
50. The primary purpose of a balanced section is to:
b. Optimize steel and concrete failure
Description: A balanced section ensures steel yields as concrete crushes, maximizing efficiency, not deflection or strength alone.
Description: A balanced section ensures steel yields as concrete crushes, maximizing efficiency, not deflection or strength alone.