(SEM VI) THEORY EXAMINATION 2024-25 DESIGN OF CONCRETE STRUCTURES

BCE601 – DESIGN OF CONCRETE STRUCTURES

Time: 3 Hours | Max Marks: 70

SECTION A – Short Answer Questions

(2 × 7 = 14 marks | Attempt ALL)
Write definition / formula + 1 key line

1. Limitations of Working Stress Method (WSM)            Assumes linear stress–strain relation

Does not represent actual failure behavior                     Uses high factor of safety → uneconomical design

2. Design Load Calculation

Given:               DL = 100 kN, LL = 150 kN, WL = 50 kN

Design Load (Limit State):
= 1.5 (DL + LL + WL)                                                       = 1.5 × (300) = 450 kN

3. Minimum Shear Reinforcement (IS Code)          Asvs=0.4bfy\frac{A_{sv}}{s} = \frac{0.4 b}{f_y}sAsv​​=fy​0.4b​ 

4. Bond Length Expression (IS 456)             Ld=ϕσs4τbdL_d = \frac{\phi \sigma_s}{4 \tau_{bd}}Ld​=4τbd​ϕσs​​ 

5. Spacing of Main Bars in Slabs (IS Code)            Maximum spacing = 3d or 300 mm, whichever is less

6. Classification of Column (Short / Long)

Short column:                       leD≤12\frac{l_e}{D} \le 12Dle​​≤12

Long column:                        leD>12\frac{l_e}{D} > 12Dle​​>12 

7. Retaining Wall        A retaining wall is a structure designed to hold back soil or earth at different levels.

SECTION B – Medium Answer

(7 × 3 = 21 marks | Attempt ANY THREE)

1. Assumptions of Working Stress Method            Plane sections remain plane

Perfect bond between steel and concrete             Concrete carries compression only

Steel and concrete obey Hooke’s law

Significance: Ensures safety but leads to conservative design.

2. Design of Shear Reinforcement (Numerical)

Steps:                                                                            Calculate nominal shear stress

Compare with permissible shear stress                        Design stirrups using IS formula

Check spacing limits                                                     (Numerical type – very important)

3. Design Procedure of Two-Way Slab (LSM)

Effective span calculation                                             Load calculation

Moment coefficients (IS 456 Table)                              Reinforcement in both directions

Check for shear and deflection

4. Codal Provisions for Columns (IS 456)

Minimum steel = 0.8%                                                 Maximum steel = 6%

Minimum bars = 4                                                        Lateral ties spacing ≤ least of:

Least lateral dimension                                                16 × dia of longitudinal bar

300 mm

5. Design of Isolated Footing

Steps:                                                                           Calculate area of footing

Check soil pressure                                                      Depth by bending & shear

Reinforcement design                                                  Development length check

(Draw neat sketch)

SECTION C – Theory / Numerical

(7 marks)

1. Moment of Resistance (WSM – Numerical)

Steps:

Calculate neutral axis depth                                      Check balanced condition

Compute resisting moment

Given:
b, d, steel area, safe stresses, m value                       2. Design Philosophies in RCC

Working Stress Method                                             Ultimate Load Method