RCC Structures MCQ With Answers for JKSSB Junior Engineer (Civil)

Technical · 2026-10-27 · 6 min read

RCC structures carried 15 marks in the board's earlier Junior Engineer (Civil) syllabus. It lists concrete technology, workability, admixtures, mix design, limit state design for flexure, shear, compression and torsion, prestressed concrete basics, and one-way and two-way slabs. Our guide to the 2026 notice shows where this section fits. The values below follow IS 456:2000, the Indian code for plain and reinforced concrete. This page gives a revision list, worked problems and solved MCQs.

Quick revision list

  • Concrete: minimum grade M20 for reinforced concrete, the 150 mm standard cube tested at 28 days, and characteristic strength as the value below which not more than 5% of results fall
  • Properties: Ec = 5000√fck N/mm² and flexural strength fcr = 0.7√fck N/mm²
  • Workability and curing: slump test, compaction factor and Vee-Bee test, and strength falls as the water-cement ratio rises. Cure OPC concrete for at least 7 days
  • Flexure: maximum concrete strain 0.0035, and the limiting moment of resistance Mu,lim = 0.138 fck bd² for Fe 415
  • Beams: minimum tension steel 0.85 ÷ fy of bd and maximum 4% of the gross area
  • Slabs: one-way when the long span is more than twice the short span, main bar spacing not more than 3d or 300 mm, and distribution steel at not more than 5d or 450 mm
  • Columns: at least 4 bars in a rectangular column and 6 in a circular one, bars of at least 12 mm, and ties of at least a quarter of the largest bar and not less than 6 mm
  • Bond: development length Ld = φσs ÷ 4τbd

Worked numerical problems

  • Modulus of elasticity: for M25 concrete, Ec = 5000 × √25 = 25,000 N/mm²
  • Flexural strength: for M20 concrete, fcr = 0.7 × √20 = 3.13 N/mm²
  • Design steel stress: for Fe 415, 0.87 × 415 = 361 N/mm²
  • Limiting moment: a beam 230 mm wide with an effective depth of 450 mm in M20 concrete and Fe 415 steel has Mu,lim = 0.138 × 20 × 230 × 450² = 128.5 kN·m. A beam needing a larger moment must be doubly reinforced
  • Minimum tension steel: for the same beam, Ast,min = (0.85 ÷ 415) × 230 × 450 = 212 mm²
  • Development length: a 16 mm deformed bar in M20 has a design bond stress of 1.2 × 1.6 = 1.92 N/mm², so Ld = 16 × 361 ÷ (4 × 1.92) = 752 mm, about 47 times the bar diameter
  • Short column capacity: a 300 mm square column in M20 with four 16 mm Fe 415 bars (804 mm²) has Pu = 0.4 × 20 × 89,196 + 0.67 × 415 × 804 = 937 kN

Under-reinforced, balanced and over-reinforced sections

In an under-reinforced beam the steel reaches its yield strength before the concrete crushes, so the beam gives visible cracking and deflection as a warning before it fails. This is the behaviour the code requires, and it is why the depth of the neutral axis is limited. An over-reinforced beam fails by sudden crushing of the concrete with the steel still elastic, which gives no warning. A balanced section reaches both limits together and is the boundary between the two.

Common mistakes

  • Using the wrong partial safety factor: concrete 1.5 and steel 1.15, not the other way round
  • Quoting 0.48d for every steel grade, when it applies to Fe 415 only
  • Mixing up the slab spacing limits: 3d or 300 mm for main bars and 5d or 450 mm for distribution bars
  • Forgetting that the minimum steel in a beam depends on fy, while the minimum steel in a slab is a fixed percentage of the gross area

Shear and bond in brief

Beams are checked for shear at a distance d from the face of the support. Where the shear stress is above what the concrete alone can carry, stirrups are provided, and they are placed closest near the supports where the shear is greatest. Bond between steel and concrete lets the two act together. Deformed bars grip better than plain bars, which is why the code allows a design bond stress 60% higher for them, and every bar must be anchored for its full development length beyond the point where it is needed.

Practise

Work the solved questions below, then read the Junior Engineer (Civil) guide for the dates and the marks for every subject. The other subject pages in this series cover fluid mechanics, mechanics and structures, and construction management.

By Shivam · Written with AI assistance and fact-checked · Questions on this page are original · Editorial policy · Report an error

Practice questions

Q1. The Indian code of practice for plain and reinforced concrete is:

  1. IS 800:2007
  2. IS 456:2000
  3. IS 875
  4. IS 1893
Show answer

IS 456:2000 — IS 456:2000 covers the design and construction of plain and reinforced concrete.

Q2. The minimum grade of concrete for reinforced concrete work under IS 456 is:

  1. M20
  2. M15
  3. M25
  4. M30
Show answer

M20 — M20 is the minimum for RCC. M15 is allowed for plain concrete in mild exposure.

Q3. The characteristic strength of concrete is the strength below which not more than:

  1. 10% of test results are expected to fall
  2. 1% of test results are expected to fall
  3. 50% of test results are expected to fall
  4. 5% of test results are expected to fall
Show answer

5% of test results are expected to fall — This is the definition of characteristic strength in IS 456.

Q4. The standard test cube for concrete has a side of:

  1. 100 mm
  2. 200 mm
  3. 150 mm
  4. 75 mm
Show answer

150 mm — The standard cube is 150 mm.

Q5. The compressive strength of concrete cubes is normally tested at an age of:

  1. 7 days
  2. 28 days
  3. 14 days
  4. 56 days
Show answer

28 days — Characteristic strength is defined at 28 days.

Q6. The partial safety factor for concrete in limit state design is:

  1. 1.5
  2. 1.15
  3. 1.0
  4. 1.25
Show answer

1.5 — Concrete 1.5 and steel 1.15 are the material factors.

Q7. The partial safety factor for steel in limit state design is:

  1. 1.5
  2. 1.0
  3. 1.25
  4. 1.15
Show answer

1.15 — The design stress of steel is fy ÷ 1.15, which is 0.87 fy.

Q8. The modulus of elasticity of concrete according to IS 456 is:

  1. 500√fck N/mm²
  2. 5000 × fck N/mm²
  3. 5000√fck N/mm²
  4. 0.7√fck N/mm²
Show answer

5000√fck N/mm² — Ec = 5000√fck. The 0.7√fck form is the flexural strength.

Q9. The flexural tensile strength of concrete according to IS 456 is:

  1. 5000√fck N/mm²
  2. 0.7√fck N/mm²
  3. 0.45 fck N/mm²
  4. 0.36 fck N/mm²
Show answer

0.7√fck N/mm² — fcr = 0.7√fck.

Q10. The maximum strain in concrete at the outermost compression fibre in flexure is:

  1. 0.0035
  2. 0.002
  3. 0.0045
  4. 0.0055
Show answer

0.0035 — IS 456 takes 0.0035 for the limit state of collapse in flexure.

Q11. The limiting value of xu,max ÷ d for Fe 415 steel is:

  1. 0.53
  2. 0.46
  3. 0.55
  4. 0.48
Show answer

0.48 — The limits are 0.53 for Fe 250, 0.48 for Fe 415 and 0.46 for Fe 500.

Q12. In an under-reinforced beam failure begins with:

  1. Crushing of the concrete
  2. Shear cracking at the support
  3. Yielding of the tension steel
  4. Slip of the bars
Show answer

Yielding of the tension steel — The steel yields first, so the failure is ductile and gives warning.

Q13. The nominal cover to reinforcement for moderate exposure under IS 456 is:

  1. 20 mm
  2. 30 mm
  3. 45 mm
  4. 75 mm
Show answer

30 mm — Mild exposure needs 20 mm, moderate 30 mm and severe 45 mm.

Q14. The minimum area of tension reinforcement in a beam is:

  1. 0.85 ÷ fy of bd
  2. 0.12% of bD
  3. 1% of bD
  4. 0.4 ÷ fy of bd
Show answer

0.85 ÷ fy of bd — As,min ÷ bd = 0.85 ÷ fy, with fy in N/mm².

Q15. The maximum area of tension reinforcement in a beam is:

  1. 2% of the gross area
  2. 6% of the gross area
  3. 1% of the gross area
  4. 4% of the gross cross-sectional area
Show answer

4% of the gross cross-sectional area — IS 456 limits it to 0.04 bD.

Q16. The maximum spacing of main reinforcement in a slab is the smaller of:

  1. 5 times the effective depth or 450 mm
  2. 2 times the effective depth or 200 mm
  3. 3 times the effective depth or 300 mm
  4. 4 times the depth or 400 mm
Show answer

3 times the effective depth or 300 mm — Distribution bars may go to 5d or 450 mm.

Q17. The minimum reinforcement in slabs with high-strength deformed bars is:

  1. 0.15% of the gross area
  2. 0.12% of the gross area
  3. 0.4% of the gross area
  4. 1% of the gross area
Show answer

0.12% of the gross area — It is 0.15% for mild steel and 0.12% for high-strength deformed bars.

Q18. A slab is designed as a two-way slab when the ratio of the longer to the shorter span is:

  1. Not more than 2
  2. More than 2
  3. More than 3
  4. Exactly 4
Show answer

Not more than 2 — Beyond a ratio of 2 the slab acts mainly in one direction.

Q19. The effective depth of a beam is measured from the extreme compression fibre to:

  1. The bottom face of the beam
  2. The neutral axis
  3. The centroid of the section
  4. The centroid of the tension reinforcement
Show answer

The centroid of the tension reinforcement — d is the distance to the centre of the tension steel.

Q20. The minimum number of longitudinal bars in a circular column is:

  1. 4
  2. 8
  3. 6
  4. 12
Show answer

6 — A rectangular column needs at least 4.

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