In this post the answer to the question given above which is faced by almost all civil engineers during their starting days at site is given below.
If you have to calculate the centre to centre spacing of bars as per the given area of the steel for a certain dia of bar you can follow the below stated procedure;
Area of Steel 'Ast req.' = 1536 sq mm
Dia of Bar to be provided 'd' = 16 mm (round bar)
Area of cross-section of 1 bar = 0.785 x d^2 = 0.785 x 16^2 = 200.96 sq mm
Spacing required = Area of 1 bar x 1000 / (Ast req.) = 200.96 x 1000 / 1536 = 130.83 mm
Hence, in the above given example spacing for 16 mm dia bar has been calculated, thus if 16 mm dia bars at 130 mm c/c are provided then the steel area provided is 1545.84 sq mm.
Now one more thing with just a little change in the formula same formula can be used for determining the Ast provided for the given Spacing;
Dia of bar = 16 mm
Spacing of bar c/c = 125 mm
Area of cross section = 200.96 sq mm
Ast provided = Area of Cross-section x 1000 / spacing = 200.96 x 1000 / 125 = 1607.68 sq mm
Thus provision of 16 mm dia bars at 125 mm c/c is provided then the area of steel provided in the region is 1607.68 sq mm.
If you have to calculate the centre to centre spacing of bars as per the given area of the steel for a certain dia of bar you can follow the below stated procedure;
Area of Steel 'Ast req.' = 1536 sq mm
Dia of Bar to be provided 'd' = 16 mm (round bar)
Area of cross-section of 1 bar = 0.785 x d^2 = 0.785 x 16^2 = 200.96 sq mm
Spacing required = Area of 1 bar x 1000 / (Ast req.) = 200.96 x 1000 / 1536 = 130.83 mm
Hence, in the above given example spacing for 16 mm dia bar has been calculated, thus if 16 mm dia bars at 130 mm c/c are provided then the steel area provided is 1545.84 sq mm.
Now one more thing with just a little change in the formula same formula can be used for determining the Ast provided for the given Spacing;
Dia of bar = 16 mm
Spacing of bar c/c = 125 mm
Area of cross section = 200.96 sq mm
Ast provided = Area of Cross-section x 1000 / spacing = 200.96 x 1000 / 125 = 1607.68 sq mm
Thus provision of 16 mm dia bars at 125 mm c/c is provided then the area of steel provided in the region is 1607.68 sq mm.
In which IS code written about this
ReplyDeleteIS456
DeleteNo IS?
ReplyDeleteThank u
ReplyDelete0.785 from where it came
ReplyDeleteArea of cross section of bar = (π/4)d^2
Deleteπ/4 = 0.785
Thanks so much. I need to understand something please. What size of steel is relevant for bridge construction? And how many steel good for abutment and pier?
ReplyDeletethanks
ReplyDeletePlease explain area of steel in tension (ast)
ReplyDeleteWhere's it in IS 456?
ReplyDeleteA big thank you for clear my doubts, I was literally searching for this calculations.
ReplyDeleteWhere did 1536mm² area of steel came from?
ReplyDelete