If d and n are the effective depth and depth of the neutral axis respectively of a singly reinforced beam, the lever arm of the beam, is

A singly reinforced beam has breadth b, effective depth d, depth of neutral axis n and critical neutral axis n?. If fc and ft are permissible compressive and tensile stresses, the moment to resistance of the beam, is

A

bn (fc/2) (d - n/3)

B

Atft (d - n/3)

C

½ n₁ (1 - n₁/3) cbd²

D

All the above

A singly reinforced beam has breadth b, effective depth d, depth of neutral axis n and critical neutral axis n₁. If f_c and f_t are permissible compressive and tensile stresses, the moment to resistance of the beam, is

A

$${\text{bn}}\frac{{{{\text{f}}_{\text{c}}}}}{2}\left( {{\text{d}} - \frac{{\text{n}}}{3}} \right)$$

B

$${\text{At}}{{\text{f}}_{\text{t}}}\left( {{\text{d}} - \frac{{\text{n}}}{3}} \right)$$

C

$$\frac{1}{2}{{\text{n}}_1}\left( {1 - \frac{{{{\text{n}}_1}}}{3}} \right){\text{cb}}{{\text{d}}^2}$$

D

All the above

A singly reinforced concrete beam of 25 cm width and 70 cm effective depth is provided with 18.75 cm² steel. If the modular ratio (m) is 15, the depth of the neutral axis, is

A

20 cm

B

25 cm

C

30 cm

D

35 cm

Consider the following statements; 1) In a reinforced concrete member subjected to flexure, the externally applied moment is resisted by an internal couple formed by steel and concrete and their magnitudes vary with the applied moment, while the lever arm of the internal couple remains constant 2) In a prestressed concrete. Member, the external moment is resisted by an internal couple, but it is the lever arm that changes with the loading conditions and the stress in steel remain practically constant Which of the above statements is/are correct?

A

1 only

B

2 only

C

Both 1 and 2

D

Neither 1 nor 2

In case of an under-reinforced beam, the depth of actual neutral axis is __________ that of the critical neutral axis.

A

Same as

B

Less than

C

Greater than

D

None of these

If the depth of actual neutral axis in a beam is more than the depth of critical neutral axis, then the beam is called

A

Balanced beam

B

Under reinforced beam

C

Over reinforced beam

D

None of the above

When the depth of the actual neutral axis in a beam is greater than the depth of the critical neutral axis, then the beam is called:

A

under-reinforced section

B

balanced beam section

C

critical section

D

over-reinforced section

Consider the following statements regarding stress in beam : 1. If a member is subjected to equal and opposite couples acting in the same longitudinal planes, the member is said to be in pure bending. 2. The internal stresses developed in the beam are known as flexural stresses. 3. There is an intermediate surface known as neutral surface, at which the stress is zero. 4. An axis obtained by intersection of the neutral surface and a cross-section is known as neutral axis. Which of the above statements are correct ?

A

2 and 3 only

B

1 and 4 only

C

3 and 4 only

D

1, 2, 3 and 4

The stresses developed in concrete and steel in reinforced concrete beam 25 cm width and 70 cm effective depth, are 62.5 kg/cm² and 250 kg/cm² respectively. If m = 15, the depth of its neutral axis is

A

20 cm

B

25 cm

C

30 cm

D

35 cm

In a doubly-reinforced beam if ‘c’ and ‘t’ are stresses in concrete and tension reinforcement, ‘d’ is the effective depth and ‘n’ is depth of critical neutral axis, the following relationship holds good

A

$$\frac{{{\text{mc}}}}{{\text{t}}} = \frac{{\text{n}}}{{{\text{d}} - {\text{n}}}}$$

B

$$\frac{{{\text{m}} + {\text{c}}}}{{\text{t}}} = \frac{{\text{n}}}{{{\text{d}} + {\text{n}}}}$$

C

$$\frac{{{\text{t}} + {\text{c}}}}{{\text{m}}} = \frac{{{\text{d}} + {\text{n}}}}{{\text{n}}}$$

D

$$\frac{{\text{m}}}{{{\text{t}} + {\text{c}}}} = \frac{{\text{n}}}{{{\text{d}} - {\text{n}}}}$$

If d and n are the effective depth and depth of the neutral axis respectively of a singly reinforced beam, the lever arm of the beam, is

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