Reinforced Cement Concrete

Q. The modulus of rupture of concrete gives

1. the direct tensile strength of the concrete
2. the direct compressive strength of the concrete
3. the tensile strength of the concrete under bending
4. the characteristic strength of the concrete

Q.

What are the types of strain?

Q. Partial safety factor for concrete and steel are 1.5 and 1.15 respectively, because

1. concrete is heterogeneous while steel is homogeneous
2. the control on the quality of concrete is not as good as that of steel
3. concrete is weak in tension
4. voids in concrete are 0.5% while those in steel are 0.15%

Q. Characteristic strength of M20 concrete is 20 MPa. What is the number of cubes having 28 days compressive strength greater than 20 MPa out of 100 cubes made with this concrete?

1. All
2. 95
3. 80
4. 50

Q. The effective width '$b_f$; of flange of a continuous T-beam in a floor system is given by

$b_t=\frac{L_0}{6}+b_w+6D_f$

where $L_0$ represents the

1. distance between points of contraflexure in a span
2. effective span of beams
3. clear span of beams
4. spacing between beams

Q. The flexural strength of M-30 concrete as per IS : 456-2000 is

1. 3.83 MPa
2. 5.47 MPa
3. 21.23 MPa
4. 30.0 MPa

Q. In limit state design method, the moment of resistance for a balanced section using M20 grade concrete and HYSD steel of grade Fe415 is given by $M_{u,lim}=Kb{d}^2$, what is the value of K?

1. 2.98
2. 2.76
3. 1.19
4. 0.89

Q. The additional cover thickness to be provided in reinforced concrete members that are totally immersed in seawater is

1. 25 mm
2. 30 mm
3. 35 mm
4. 40 mm

Q. A T-beam roof section has the following particulars:

Thickness of slab : 100mm
Width of rib : 300mm
Depth of beam : 500mm
Centre to centre distance of beams : 3.0 m
Effective span of beams : 6.0m
Distance between points of contraflexur :3.60m

The effective width of flange of the beam is

1. 3000mm
2. 1900mm
3. 1600mm
4. 1500mm

Q. A singly reinforced rectangular concrete beam of width 300 mm and effective depth 400 mm is to be designed using M25 grade concrete and Fe500 grade reinforcing steel. For the beam to be under-reinforced, the maximum number of 16 mm diameter reinforcing bars that can be provided is

1. 3
2. 4
3. 5
4. 6

Q. If the characteristic strength of concrete $f_{ck}$ is defined as the strength below which not more than 50% of the test results are expected to fail, the expression for $f_{ck}$ in terms of mean strength $f_m$ and standard deviation $\overline{\sigma }$ would be

1. $f_m-0.1645\overline{\sigma }$
2. $f_m-1.645\overline{\sigma }$
3. $f_m$
4. $f_m+1.645\overline{\sigma }$

Q. The maximum depth of neutral axis for a beam with 'd' as the effective depth, in limit state method of design for Fe 415 steel is

1. 0.46d
2. 0.48d
3. 0.50d
4. 0.53d

Q. The target mean strength $f_{cm}$ for concrete mix design obtained from the characteristic strength $f_{ck}$ and standard deviation $\sigma$ as defined in IS 456-2000 is

1. $f_{ck}+1.35\sigma$
2. $f_{ck}+1.45\sigma$
3. $f_{ck}+1.55\sigma$
4. $f_{ck}+1.65\sigma$

Q. The flexural tensile strength of M25 grade of concrete in N/mm${}^2$ as per IS:456-2000 is _______.

1. 3.5

Q. Factor of safety is the ratio of

1. tensile stress to working stress
2. compressive stress to working stress
3. bending stress to working stress
4. yield stress to working stress

Q. A rectangular beam of 230 mm width and effective depth = 450 mm, is reinforced with 4 bars of 12 mm diameter. The grade of concrete is M 20, grade of steel is Fe500. Given that for M20 grade of concrete, the ultimate shear strength ${\tau }_{uc}=0.36N/m{m}^2$ for steel percentage of p = 0.25, and ${\tau }_{uc}=0.48N/m{m}^2$ for steel percentage p = 0.5. For a factored shear force of 45 kN, the diameter (mm) of Fe500 steel 2 legged stirrups to be used at spacing of 375 mm should be

1. 8
2. 10
3. 12
4. 16

Q. The characteristic strength of concrete is

1. higher than the average cube strength
2. lower than the average cube strength
3. the same as the average cube strength
4. higher than 90% of the average cube strength

Q. A simply supported beam has an effective span of 16 m. What shall be the limiting ratio of span to effective depth as per IS 456- 2000?

1. 26
2. 20
3. 12.5
4. 7

Q. What is the minimum area of tension reinforcement in beams when Fe 415 is used?

1. 0.8%
2. 0.12%
3. 0.15%
4. 0.2%

Q. As per the provision of IS 456-2000, in the limit state method for design of beams, the limiting value of the depth of neutral axis in a reinforced concrete beam of effective depth 'd' is given as

1. 0.53d
2. 0.48d
3. 0.46d
4. Any of the above depending on the different grades of steel.

Q. For a reinforced concrete beam section the shape of the shear stress diagram is

1. Parabolic over the whole section with maximum value at the neutral axis
2. Parabolic above the neutral axis and rectangular below the neutral axis
3. Linearly varying as the distance from the neutral axis
4. Dependent on the magnitude of shear reinforcement provided

Q. Consider the following statements:
Percentage of steel for balanced design of a singly reinforced rectangular section by limit state method depends on

1. Characteristic strength of concrete.
2. Yield strength of concrete.
3. Modulus of elasticity of steel.
4. Geometry of the section.
Which of these statements are correct?

1. 2, 3 and 4
2. 1, 3 and 4
3. 1, 2 and 4
4. 1, 2 and 3

Q. A T-beam of flange width 1200 mm, flange thickness 100 mm, rib width 275 mm has an effective depth of 550 mm and is reinforced with 6 bars of 25 mm$\varphi$. The ultimate MOR will be ____ kNm. [Use M30 concrete and Fe415 steel]

1. 400
2. 800
3. 548.21
4. 100

Q. Modulus of elasticity of concrete is increased with

1. Higher W/C ratio
2. Shorter curing period
3. Lesser vibration
4. Increase in age

Q. Minimum shear reinforcement in beams is provided in the form of stirrups

1. to resist extra shear force due to live load
2. to resist the effect of shrinkage of concrete
3. to resist principal tension
4. to resist shear cracks at the bottom of beam

Q. Considering modular ratio as 13, grade of concrete as M20 and grade of steel as 415, what is the ratio of balanced depth of neutral axis as per working stress method to the balanced depth of neutral axis as per limit state method?

1. $\frac{12}{7}$
2. $\frac{11}{3}$
3. $\frac{7}{12}$
4. $\frac{3}{11}$

Q. A reinforced concrete beam of rectangular section has a width of 300 mm and an effective depth of 500 mm. The effective cover to tension and compression steel is 40 mm each. The beam is reinforced with 4 bars of 20 mm diameter in tension and 2 bars of 16 mm diameter in compression. The grade of concrete used is M20 and steel is Fe145.
The depth of neutral axis is ____ mm.
[Assume $f_{sc}$ = 0.97 times allowable stress in tension steel]

1. 146.53

Q. For maximum sagging bending moment at
support in a continuous RC beam, live load
should be placed on

1. spans adjacent to the support plus alternate spans
2. all the spans except the spans adjacent to the support
3. spans next to the adjacent spans of the support plus alternate spans
4. spans adjacent to supports only

Q. Doubly reinforced beams are recommended when

1. the depth of the beam is restricted
2. the breadth of the beam is restricted
3. both depth and breadth are restricted
4. the shear is high

Q. A prestressed concrete beam 150 mm $\times$ 300 mm supports a live load 5 kN/m over a simple span of 8 m. It has a parabolic cable having an eccentricity of 75 mm at mid-span and zero at the ends. The prestressing force required to maintain the net resultant stress at the bottom fibre at mid-span as zero under the action of DL + LL + prestress is

1. 239 kN
2. 293 kN
3. 302 kN
4. 392 kN