Civil Engineering MCQJE Level Civil Engineering
The development length (Ld) of a bar in tension is given by IS 456 as:
RCCRCCMEDIUM
Choose the correct answer
A
Ld = φ·fy/(4τbd)
B
Ld = φ·σs/(4τbd) where σs = 0.87fy
C
Ld = φ·fck/(τbd)
D
Ld = 4φ·σs/τbd
Correct Answer
B. Ld = φ·σs/(4τbd) where σs = 0.87fy
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Ld = (φ × σs)/(4 × τbd) where φ = bar dia, σs = design stress in bar = 0.87fy, τbd = design bond stress. For Fe415 in M20 concrete: τbd = 1.2 × 1.6 = 1.92 MPa (deformed bar). Ld ensures the bar reaches full yield stress at the critical section without pulling out.
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