Category: Reinforced Steel Structures

Tension & Compression on beams

Various beams react differently to the load acted on them, let us go through following 2 beams

  • Simply Supported beams & Continuous beams

simply-supportted-beam-civilmafia-in

For simply supported beams,

Compression acts on the top side whereas tension acts on the bottom side.
  • Cantilever Beams

cantilever-beams

Cantilever beams react differently than continuous beams,

In Cantilever beams, compression acts on the bottom side where as tension acts on the top side
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USEFUL TIPS FOR CIVIL ENGINEERING INTERVIEW

USEFUL TIPS FOR CIVIL ENGINEERING INTERVIEW

GRADE OF CONCRETE:

M5 – 1 : 4 : 8

M10 – 1 : 3 : 6

M15 – 1 : 2 : 4

M20 – 1 : 1.5 : 3

M25 – 1 : 1 : 2


CLEAR COVER TO MAIN REINFORCEMENT:

Footings : 50 mm

Raft Foundation Top : 50 mm

Raft Foundation Bottom : 75 mm

Raft Foundation Side : 75 mm

Beam : 25 mm

Strap Beam : 50 mm

Column :40 mm

Slab : 15 mm

flat Slab : 20 mm

Staircase : 15 mm

Retaining Wall : 20 – 25 mm

Water Retaining Structures : 2 0- 30 mm


Maximum water absorption by bricks – 15%

Compressive strength of bricks – 3.5 N/mm2

Density Of Bricks- 1600-1920 Kg/m3

Minimum thickness of slab – 125 mm

Dimension tolerance for cubes – +2

Maximum free fall of concrete – 1.50 m

Lapping should not be used for the bars having larger dia than 36 mm.

Binding wire required for steel reinforcement – 8 kg per MT

3 samples should be taken for every 100 m2 in core cutting test.

Maximum chair spacing – 1 m.

Minimum dia should be used in dowels rod – 12 mm.

Hook for strriups (one side) – 9D

No. of strriups = (clear span/spanning) + 1

Length of main steel in cantilever anchorage – 69D.

Minimum no. of bars in square column – 4

Minimum no. of bars in circular column – 6

Minimum dia of main bars and distributors in the slab – 8 mm.

Maximum dia of  main bars and distributors in the slab – 1/8 of slab thickness.

All reinforcement should be free from mill scales, loose rust, and coats of paints , oil or any other substances.


SETTING TIME:

Initial setting time should not be less than 30 minutes.

Final setting time should not be greater than 10 hours.

REQUIRED CURING DAYS:

Super sulfate cement – 7 days

Ordinary portland cement – 10 days

Cement with minerals and admixtures – 14 days.

SLUMP VALUE (IS456):

Lightly reinforced concrete : 25 – 75 mm.

Heavily reinforced concrete : 75 – 100 mm.

Trench fill : 100 – 150 mm ( for in-situ & tremie).

CUBE SAMPLES:

1 – 5 m3 : 1 No.

6 – 15 m3 : 2 No..

16 – 30 m3 :3 No.

31 -50 m3 : 4 No.

Above 50 m3 : 4 + 1 no. of addition for each 50 m3.

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Stress Strain and Young’s Modulus

  • Stress–  Force applied on a body per Unit area is called as stress.stresscivilIt can be denoted by Stress= Force/Area.
  • Strain– When a body is subjected to tensile force, the body undergoes change in length.

Change in length of the body to the original length is known as Strain.

Strain = Change in Length / Original Length

sttraincivil

  • Modulus of Elasticity / Young’s Modulus

Modulus of elasticity is the ratio of stress to the strain induced in a body

Young’s modulus is denoted by E

E= Stress / Strain

Why Steel is used in Concrete for RCC structures ?

Below are the Reasons why steel is used in RCC structure not some other Metals, Non-metals or Alloys

  1. It is cheap and Easily available
  2. It possesses very high Tensile strength & elasticity
  3. It develops good bond with concrete
  4. Coefficient of expansion(12.6 X 10^-6) of steel is nearly equal to the same of concrete (14 X 10^-6) which means concrete and steel expand and shrink with almost same volume change when exposed to heat or cold.

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