Slab base for ISHB 350@710.2, 1000 kN

Data: ISHB 350 @ 710.2 N/m (72.4 kg/m): $h=350$, $b_f=250$, $t_f=11.6$, $t_w=10.1$ mm. Factored load $P=1000$ kN; pedestal M20; steel E250 ($f_y=250$).

1. Bearing strength of concrete (IS 800:2007 cl. 7.4.1)

$0.45f_{ck}=0.45\times20=9.0$ N/mm²

2. Plate size

$$A_{req}=\frac{1000\times10^3}{9.0}=111111\ \text{mm}^2$$

Provide equal projections of 50 mm: $L=350+2\times50=450$ mm, $B=250+2\times50=350$ mm. Area $=157500$ mm² $>A_{req}$ ✓

$$w=\frac{1000\times10^3}{450\times350}=6.35\ \text{N/mm}^2<9.0$$

3. Thickness (cl. 7.4.3.1)

Projections $a=b=50$ mm:

$$t_s=\sqrt{\frac{2.5w(a^2-0.3b^2)\gamma_{m0}}{f_y}}=\sqrt{\frac{2.5\times6.35\times(50^2-0.3\times50^2)\times1.10}{250}}=11.06\ \text{mm}$$

Also $t_s\ge t_f=11.6$ mm. Provide $t_s=12$ mm.

4. Connections

• Column to plate: 6 mm fillet weld all round (nominal; column end machined for bearing).
• Anchor bolts: 4 nos. M20 (minimum), embedded 450 mm, with washer plate, placed outside the flanges.

Answer: base plate 450 × 350 × 12 mm, 4 anchor bolts M20, 6 mm weld.