D21 Oct 8 Btech 1 yr-Doubly reinforced beam&Codal provisions

A simply supported RCC slab has an effective depth of 80 mm and rests on two 230 mm masonry walls. The centre-to-centre distance between walls is 3.30 m. As per IS 456 : 2000, the effective span (in m) is ______.

• 3.38

• 3.30

• 3.15

• 2.90

For a continuous RCC beam (span ≤ 10 m), the basic span-to-effective-depth ratio specified by IS 456 is approximately ______.

• 20

• 24

• 26

• 28

In a doubly reinforced beam, the distance between the line of action of resultant compression and resultant tension is called ______.

• Effective depth

• Lever arm

• Overall depth

• Neutral axis

A doubly reinforced beam is preferably adopted when ______.

• Depth > 1 m

• Very small moments are expected

• Depth and breadth must be restricted while carrying larger moments

• Extra safety is needed only against shear

For spans > 10 m; for spans ≤ 10 m, f₁ = 1.0 (max 1.0).

• True

• False

For normal rectangular beams (not T or L beams), the reduction factor f₄ is taken as 1.0.

• True

• False

Assertion (A): For serviceability, IS 456 specifies that when all loads (including temperature, creep, shrinkage plus finishes and partitions) act, the maximum deflection = lesser of span/350 and 20 mm. Reason (R): IS 456 provides basic span/depth ratios that generally ensure deflection limits are satisfied.

• Both A and R true, R correct explanation

• Both A and R true, R not explanation

• A true, R false

• A false, R true

The lowest grade of concrete permitted for RCC works as per IS 456 is _________.

The maximum percentage of tensile reinforcement in an RCC beam shall not exceed ________ % of its gross cross-sectional area.

For a beam span of 12 m, the span-based modification factor f₁ = 10 / span = ________.