Answer / santosh singh

1) overlap= during placing steel for RCC structure if the
required length of bar is not available then lapping ie.
placing two bars side by side for a designed length is done.

lap length is in between 40d to 60d where d= diameter of
the bar. but if overlap length is not given 50d value is
assumed

eg, if dia of bar is 12mm then
lap length= 50x 12 = 600mm

2)Development length= (nominal diameter of bar x stress in
bar) / (4 x design bond stress )

if d=12 mm
stress in bar =415 N/mm2
design bond stress for M20 CONCRETE = 1.2 N/mm2
then,
Ld = 12 x 415 /4 x 1.2 = 1037mm say 1m

this length is for steel in tension while development
length for steel in compression is 25 % less

ie in compression zone development length for same detail
will be = 1- 25/100x1= 1-.25 =0.75m ie 750mm

Answer / madhukeshwara`

d=16 mm for compression steel
stress in bar =0.87 times of 415 N/mm2 = 361.05N/mm2
design bond stress for M20 CONCRETE = 1.2 N/mm2
then,
Ld = 16 x 361.05 /4 x 1.6X 1.2 = 752.02 mm

d=16 mm for tension steel
stress in bar =0.87 times of 415 N/mm2 = 361.05N/mm2
design bond stress for M20 CONCRETE = 1.2 N/mm2
then,
Ld = 16 x 361.05 /4 x 1.25X 1.2 = 962.8 mm

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