Iterative calculation to establish K and hence As

Make initial assumption of K2 = 1 This gives e,, = 136.4 mm tot

Nlbhfck = 2500 x 103/(400 x 400 x 30) = 0.52 Mlbh2fc^= 136.4 x 2500 x 103/(4003 x 30) = 0.178 d'lh = 60/400 = 0.15 Using chart in Section 13, Figure 13.2(c) gives K2 = 0.69 Take this modified value of K2 to recalculate e . Therefore e,, = 13.2 + 22 + 101.2 x 0.69 = 105.0 mm tot

Hence

This reduces K2 to 0.62 and Mlbh\ to 0.128 Try reduction of K2 to 0.60

This gives Mlbh2fck = 0.125 which corresponds to K2 = 0.60 in the chart. Hence s yk = 0.38

bhf.

= 3965 mm2

Use 4T32 and 2T25 (4200 mm2)

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