Quiz: Civil Engineering

Exam: DFCCIL EXECUTIVE

Topic: MISCELLANEOUS

Each question carries 1 mark

Negative marking: 1/4 mark

Time: 10 Minutes

Q1. Creep of a materials is?

(a) disappearance of deformation on removal of load

(b) to become brittle

(c) not being ductile

(d) continued deformation with time under sustained loading

Q2. As per IS specifications, the nominal concrete cover for moderate exposure should not be less than…………..

(a) 20 mm

(b) 30 mm

(c) 45 mm

(d) 50 mm

Q3. According to working stress method, the limiting value of permissible tensile stresses for a reinforced concrete member in tension for HYSD of grade Fe415 is:

(a) 190

(b) 230

(c) 250

(d) 415

Q4.Partial safety factors for concrete and steel respectively may be taken as:

(a) 1.5 and 1.15

(b) 1.5 and 1.78

(c) 3 and 1.78

(d) 3 and 1.2

Q5. Consider the following statements:

At a point of inflection, the embedment length need not exceed the development length L_d

The condition that L_d≤(M_1/V+L_0 ) need not be checked for negative reinforcement.

At least one-third of the total negative reinforcement provided must extend beyond the point of inflection for a distance not less than ‘d’ or 12ϕ or clear – span whichever is larger.

Which of these statements are correct?

(a) 1, 2 and 3

(b) 1 and 2

(c) 1 and 3

(d) 2 and 3

Q6. The development length in compression for a 20 mm diameter deformed bar of grade Fe 415 embedded in concrete of grade M 25 whose design bond stress is 1.40 N/mm², is

(a) 1489 mm

(b) 1289 mm

(c) 806 mm

(d) 645 mm

Q7. The critical section for two-way shear of footing is at the

(a) face of the column

(b) distance d from the column face

(c) distance d/2 from the column face

(d) distance 2d from the column face

(Where d is the effective depth of the footing)

Q8. In a combined footing for two columns carrying unequal loads, the maximum hogging moment occurs at

(a) inside face of the heavier column

(b) a section equidistant from both the columns

(c) a section having maximum shear force

(d) a section having zero shear force

Q9. Elastic Modulus of Steel is *__*

(a) 1.5 x 109 N/mm2

(b) 2.0 x 105 N/mm2

(c) 2.0 x 105 N/m2

(d) 1.5 x 109 N/m2

Q10. In a fillet weld the weakest section is the

(a) smaller side of the fillet

(b) throat of the fillet

(c) side perpendicular to force

(d) side parallel to force

SOLUTION

S1. Ans.(d)

Sol. when concrete is subjected to sustained compressive load (Dead load) its deformation keep increasing with time even stress is not change. Time dependent component of total strain excluding that of shrinkage & temperature is termed as creep.

S2. Ans.(b)

Sol.

Exposure condition Minimum grade Minimum cover

Mild M20 20mm

Moderate M25 30mm

Sever M30 45mm

Very sever M35 50mm

Extreme M40 75mm

S3. Ans.(b)

Sol. Permissible stress in steel reinforcement

Type of stress Mild steel Fe415 Fe500

Tension & shear

ϕ≤20 mm

ϕ>20 mm

140 Mpa

130 Mpa

230 Mpa

275 Mpa

Compression 130 Mpa 190 Mpa 190 Mpa

S4. Ans.(a)

Sol. In limit state method.

Partial safety factor for RCC = 1.5

Partial safety factor for steel = 1.15

In working state method.

Partial safety factor for R.C.C. = 3

Partial safety factor for steel = 1.78

S5. Ans.(b)

Sol. The development L_d=(ϕσ_s)/(4τ_bd )

ϕ → nominal diameter of the bar.

ϕ_s→ stress in bar at the section considered at design load.

τ_bd → design bond stress

At simple supports and at points of inflection. Positive moment tension reinforcement shall be limited to a diameter such that

L_d= ≤M_1/V+L_0

This condition need not to be checked for negative reinforcement.

S6. Ans.(d)

Sol. According to IS 456 : 2000

The development length (L_d ) = (ϕσ_st)/(4τ_bd )

→ For deformed bars τ_bd shall be increases by 60%.

→ for bar’s in compression τ_bd increased by 25%

L_d=(20×0.87×415)/(4×1.4×1.6×1.25)

▭(L_d= 645 mm)

S7. Ans.(c)

Sol. Critical section for one way shear: The footing acting essentially as a wide beam, with a potential diagonal crack extending in a plan across the entire width, the critical section for this condition shall be assumed as a vertical section located from the face of the column, pedestal or wall at a distance equal to effective depth (D) of the footing in case of footings on soils and distance d/2 of the footing for footings on piles.

Critical section for two way shear: Two way action of the footing, with potential diagonal cracking along the surface of truncated cone or pyramid around the concentrated load. The distance of critical section from the periphery of the column shall be taken at d/2.

S8. Ans.(d)

So. The combined footing resists the load by bending in two direction. The footing in the longitudinal direction is subjected to a sagging moment in the cantilever portion and under the columns; and hogging moment in the central portion between the columns. Footing in the transverse direction develops sagging moments.

Thus maximum hogging moment occurs in the central portion where shear force is zero.

S9. Ans.(b)

Sol. Steel is an alloy of iron and carbon. Apart from carbon, a small percent of manganese, Sulphur, phosphorous, nickel and copper are added to give special properties to steel. Steel has high durability and strength but it has very small resistance against fire and corrosion. Elastic modulus of steel is 2 × 10^5 N/mm² and Unit mass of steel is 7850 kg/m³.

S10. Ans.(b)

Sol. The part of the weld which is assumed to be effective in transferring the stress is called throat. Throat thickness is the minimum dimension in the fillet weld, so in a fillet weld the weakest section is the throat of the fillet.