Development Length of Bars

  What is Development Length of Bars

The calculate tension or compression in any bar at any section shall be development on each size the section by any appropriate development length or end anchorage or by combination thereof .

Development length of Bars Ld

Ld =ɸ x  бa/4 Xτbd

Where

ɸ = Nominal dia of the bars  

бa = stress in the bar in the consider in design load

τbd = design load bond stress 

Design bond stress in limit state method for plain bar

Grade of concrete

M20

M25

M30

M35

`M40

Design bond stress

τbd N/mm2

1.2

1.4

1.5

1.7

1.9

For deformed bars conforming to IS 1786 this value conforming to IS 1786 this value shall be be 60 percent 

for bras in compression, the values of bond stress for bars in tension shall be inceeased by 25 percent .


Example :

assume stress in a bar consider 550D

M30 concrete ,and dia is 20mm

Ld =ɸ x  бa/4 xτbd

Ld =20 x550 /4 X 1.5

Ld=1834mm

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