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 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

If the permissible compressive and tensile stresses in a singly reinforced beam are 50 kg/cm² and 1400 kg/cm² respectively and the modular ratio is 18, the percentage area A_st of the steel required for an economic section, is

A

0.496%

B

0.596%

C

0.696%

D

0.796%

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

d

B

n

C

$${\text{d}} + \frac{{\text{n}}}{3}$$

D

$${\text{d}} - \frac{{\text{n}}}{3}$$

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

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

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

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

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

If the permissible stress in steel in tension is 140 N/mm², then the depth of neutral axis for a singly reinforced rectangular balanced section will be

A

0.35 d

B

0.40 d

C

0.45 d

D

Dependent on grade of concrete also

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

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

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