HOW TO CALCULATE DEVELOPMENT LENGTH

DEVELOPMENT LENGTH CALCULATION

A development length can be defined as the amount of reinforcement(bar) length needed to be embedded or projected into the column to establish the desired bond strength between the concrete and steel.

CALCULATION:-
We have a M25 grade of concrete and FE500 grade of steel.
Diameter of bar is 20 mm

FORMULA:-
Where,
Ld            = development length of bar
 Ø           = nominal dia of reinforcement bar
 6s          = Stress in bar at the section considered at design load
Tbd         = Design bond stress
 As per IS 456-2000 CL 26.2.1.1

Design Bond Stress in Limit State Method
M20M25M30M35M40 and above
Concrete Grade1.21.41.51.71.9For Plain Bars in Tension
Design Bond Stress (tbd,N/mm2)1.922.242.42.723.04For HYSD bars in tension

Ld = 500 x 0    =  55.80  = 56 0
                4 x 2.24

hence, Ld = 56 0 = 56 x 20 = 1120 mm is required.

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