(SEM V) THEORY EXAMINATION 2017-18 DESIGN OF CONCRETE STRUCTURES -I

DESIGN OF CONCRETE STRUCTURES–I (NCE-505)

B.Tech | Semester V | Section-wise Important Questions & Notes

SECTION A – Very Short Answer (2 × 10 = 20 Marks)

Focus: crisp definitions, code values, and basic concepts. Write 1–2 lines only.

Important Questions

What is modular ratio?                                    Determine modular ratio for M20 concrete.

What is effective depth of a beam?                 Minimum grade of concrete for RCC as per IS 456:2000.

What is measured in slump cone test?            Define neutral axis.

What is effective cover?                                   Define lever arm.

What is creep of concrete?                               What is shrinkage of concrete?

Key Notes

Modular ratio m=2803σcbcm = \frac{280}{3\sigma_{cbc}}m=3σcbc​280​ (WSM); for M20, m=13.33m = 13.33m=13.33.

Effective depth = distance from compression face to centroid of tensile steel.

Min concrete grade (RCC): M20.

Slump test → workability.

SECTION B – Short Answer (Attempt Any 3) (10 × 3 = 30 Marks)

Focus: concepts + assumptions + key formulas (with neat sketches where asked).

Important Questions

Water–cement ratio: definition, importance, effects on strength & durability.

Assumptions of Working Stress Method (WSM).

Under-reinforced vs Over-reinforced sections (behavior & failure).

Moment of resistance (MOR) formulas for under- and over-reinforced sections (with diagram).

Critical section and critical neutral axis.

Key Notes
 

WSM assumes linear stress–strain; plane sections remain plane.

Under-reinforced → ductile (steel yields first).    Over-reinforced → brittle (concrete crushes first).

Know MOR expressions and lever arm relation.

SECTION C – Numerical (Attempt Any One) (10 Marks)

Focus: MOR of singly reinforced rectangular beams using WSM.

Typical Problems

Given b,db, db,d, steel details, allowable stresses in concrete & steel, find MOR.

Use M20, Fe as specified; m=13.33m = 13.33m=13.33.

Solving Steps

Compute neutral axis depth xxx.            Check permissible stresses (governing material).

Find lever arm zzz.                                   Compute MOR.

Show steps clearly; box the final answer.