**Important 1000 MCQ For CIVIL Junior Engineer**

**21. The velocity of exit waste gases****should be a minimum of ____ of wind****speed to prevent down draught.**

A. 0.5 B. 1.5

C. 2.5 D. 3.5

**Ans. C**

**Solution**.

- The velocity of exit, ve should be the min. of 2.5 of wind speed to prevent down draught. It can be see in rocket in which, Ve = me√yRTe Where y is specific heat ratio.

**22. The device used for the easy****separation of dry dust of 10 to 100****µm size is ______.**

A. cyclone

B. gravity settling chamber

C. bag filter

D. scrubber

Ans. A

**Solution **

- A cyclonic separation is a method of removing particulates from an air, gas or liquid stream, without the use of filters, through vortex separation. When removing particulate matter from liquids, a hydrocyclone is used; while from gas, a gas cyclone is used.

**23. Consider the following factors**

A) Large number of loading cycles

B) Large variations in stress

C) Large stress concentrations

Those associated with fatigue failure

would include ________.

A. A and B B. A and C

C. B and C D. A, B and C

**Ans. D**

**Solution : **

- In case of loading, the fatigue condition will occur when load is applied zero-to-max-to-zero & when varying load or stresses acting on member. In case of stress, the fatigue condition will occur when any tensile stress is acting on a member & then released suddenly.

**24. In a truss girder of a bridge, a****diagonal consists of mild steel flat 400****ISF and carries a pull of 800 kN. If the****gross diameter of the rivets is 26mm,****then the number of rivets required in****the splice is ______.**

A. 6 B. 7

C. 8 D. 9

Ans. D

**Solution : **

- Strength of the one rivet = 2.5kb.d.t.fu/ymo

Where, ymo is factor of safety

Kb is least of ( P/3d0)-.25, e/3d0, 10. Whichever is less.

Kb = 0.523 & for 400 ISF t = 8mm.

So, strength of one rivet = 2.5 × 0.523 × 26 × 8 × 400/1.25 = 87.027 kN

No of rivets = 800/87.027 = 9.1

**25. The problem of lateral buckling can****arise only in those steel beams which****have ______.**

A. moment of inertia about the

bending axis larger than the other

B. moment of inertia about the

bending axis smaller than the other

C. fully supported compression

flange

D. None of these

**Ans. B**

**Solution: **

- From the relation, P = ∏2EI/L2 So the buckling is depend on moment of inertia about the bending axis. Lateral buckling occur when the moment of inertia about the bending axis will be smaller than other.

**26.For unstiffened flange of a beam in****flexural compression, the maximum****allowable outstand is equal to****______.**

A. 20 t B. 16 t

C. 32 t D. 14 t

**Ans. B**

**Solution : **

- for un-stiffed flange The max. allowable outstand = least of 16t or 200mm. whichever is less.

**27. And angle section can be used as****purlin when slope of the roof truss is****_______.**

A. Between 40° and 70°

B. Less than 30°

C. Greater than 30°

D. Less than 45°

**Ans. B**

**Solution : **

**28. The buckling load in a steel column is****_______.**

A. inversely proportional to square of

length

B. Directly proportional to the

slenderness ratio

C. Inversely proportional to the

slenderness ratio

D. Directly proportional to length

**Ans. C**

**Solution: **

- The buckling load, P = ∏2EI/L2 p is inversely proportional to the slenderness ratio

**29. The effective length of battened****column is increased by _____.**

A. 10% B. 7%

C. 12% D. 25%

**Ans. A**

**Solution: **

- The actual length L of the compression member should be taken as the length from centre-to-centre of intersection of supporting members or the cantilevered length in the case of free standing struts. & the effective length increased by 10% for battened columns.

**30. Angle of inclination of the lacing bar****with the longitudinal axis of the****column should preferably be between****_______.**

A. 10° to 30° B. 30° to 80°

C. 40° to 70°. D. 20° to 70°

**Ans. C**

**Solution**

- Lacing bar shall be inclined at 400 to 700 to axis of built up member or longitudinal axis of the member.