Calculation of Lengths of Different Types of Bars

For calculating the lengths of bars, appropriate values of cover, anchorage length and development lengths are to be used.

Length of straight bar with hooks

Length of straight bar with hooks

= Total length of beam – 2 x End cover + 2 x 9Ø

= Clear span + 2 x (bearing) – 2 x End cover + 18Ø

Length of straight bar without hook

= Total length of beam – 2 x End cover

= Clear span + 2 x (bearing) – 2 x End cover

Length of bent up bar in beams (Fig. 2)

H = D – 2 x Clear cover – 2 × Dia. of stirrups – Dia. of main bar

Where D is the total depth of the beam.

Length of bent up bar

= Length of straight bar – 2H + (1.42H) x 2

= Length of straight bar – 2H + 2 × 1.42H

= Length of straight bar + 2 x 0.42H

Length of bent up bar in slabs

Length of bent up bar Length of straight bar + 2 x 0.42H

Where                  H = D – 2 x Clear cover – Dia. of main bar

D is the total depth of slab

(Stirrups are not provided in slabs)

Length of Stirrups in beams (Fig. 3)

Assuming the hook at the end of stirrup bar around the main bar for a length of 12d (d is the dia. of stirrup bar).

Length of one stirrup bar = 2(A + E) + 2 x 12 x Dia. of stirrup bar

Where

A = D – 2 x Clear cover – 2 x Dia. of bar for stirrup

E = b – 2 × Clear cover – 2 x Dia. of bar for stirrup

b and D are breadth and depth of beam section

No. of stirrups = (Centre to centre of bearing / spacing of stirrups) + 1

Length of spiral ties in columns where P is not greater than D/5 (Fig. 4)

Length of spiral = Nπ (D + d) + 8d

Where

N = No. of complete and fractional turns

D = Internal dia.

P = Pitch of helix

d = Size of bar

Length of Spacer bars (Fig. 5)

Spacer bars are used to separate two rows of main bars

Length of spacer bar = b – 2 x clear cover

 

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