In this article we shall discuss

1 - Derivation of D²/162.131 in details

2- How to calculate weigh of steel bar with example

*We know that*

*Mass = volume × Density*

*Calculation to calculate the volume of steel bar -**Length = 1 met. = 1000 mm*

*Let us consider that the steel bar is of circular shape. So*

*Area of bar =*

__(__π/4)× D² square mm

*Where 'D' is diameter of steel bar in millimetre ("Diameter is considered in mm because steel bars come with diameter specified in millimetre in market. Viz. 8mm Φ, 16 mmΦ, 20mm Φ")*

Then

**Volume of bar= length of bar ×area of bar**

= 1000×(

*π /4)*×*D*² = 1000 x (*π/4)*D² cubic mmTo convert the volume in cubic metre from cubic mm

We know that

1 cubic mm = 10^(-9) cubic metre

=

1 cubic mm = 10^(-9) cubic metre

=

__1__cubic metre
(1000× 1000 ×1000)

Then volume in cubic metres can be calculated as-

Then volume in cubic metres can be calculated as-

=

(4× 1000× 1000 ×1000)

__1000× π × D²__(4× 1000× 1000 ×1000)

=

( 4 × 1000 ×1000)

We know that

__πD²__cubic metre( 4 × 1000 ×1000)

We know that

**Density of steel bar = 7850 kg/m^3**
Hence

Mass = Volume × density

After putting the value in above formula

Mass =

( 4 ×1000 ×1000 )

Mass = Volume × density

After putting the value in above formula

Mass =

__π × D² × 7850__m^3 (KG /m^3)( 4 ×1000 ×1000 )

=

( 4 ×1000 ×1000 )

After calculation we'll get-

Where 'D' is the diameter of steel bar in mm

__π × D² × 7850__KG( 4 ×1000 ×1000 )

After calculation we'll get-

**Mass =**__D²__**162.131**Where 'D' is the diameter of steel bar in mm

○Example - calculate the weight of 16 mm diametre of steel bar if the length of bar is 12 met.

Solution-

Diameter of bar(D)= 16 mm

Length of bar = 12 met.

We know that

=

162.131

=

162.131

Weight of 1 met.16 mm diameter Steel bar= 1.579 KG

Solution-

Diameter of bar(D)= 16 mm

Length of bar = 12 met.

We know that

**Weight of 1 met. Steel bar = D² /162.131 KG**=

__16²__162.131

=

__16 × 16__162.131

Weight of 1 met.16 mm diameter Steel bar= 1.579 KG

Weight of 12 met. Length steel bar =

= 12 × weight of 1 met. Steel bar

= 12 × 1.579

= 18.948 KG

Note- same method can be used to calculate the weight of various diameters steel bars.

Thank you

www.Gyanofcivilengineering.com

Mukesh Kumar

= 12 × weight of 1 met. Steel bar

= 12 × 1.579

= 18.948 KG

Note- same method can be used to calculate the weight of various diameters steel bars.

Thank you

www.Gyanofcivilengineering.com

Mukesh Kumar

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