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Bar spacing in a slab

Spacing of bars for a required area of steel per metre, with the maximum spacing for main bars. Reference: IS 456:2000 Cl. 26.3.3(b).

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# Data
A_req := 420 mm^2
phi := 10 mm
d := 125 mm

# Spacing
a_b := pi/4*phi^2 = mm^2
s_calc := 1000 mm*a_b/A_req = mm
s_max := min(3*d, 300 mm) =
s := floor(min(s_calc, s_max)/(10 mm))*10 mm = mm
A_prov := 1000 mm*a_b/s = mm^2

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