Slab base for ISSC 200, 1200 kN

Assumption: the section "ISSC 200" (SC 200) is taken with overall size $h=200$ mm, $b_f=200$ mm and flange thickness $t_f\approx15$ mm (only these three values are needed for the base plate). Factored axial load $P=1200$ kN, pedestal M20, E250 steel.

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

$0.45f_{ck}=0.45\times20=9.00$ N/mm²

2. Plate size

$$A_{req}=\frac{P}{0.45f_{ck}}=\frac{1200\times10^3}{9.00}=133333\ \text{mm}^2$$

Projection of about 85 mm all round the column (not less than 50 mm): $L=200+2\times85=370$ mm, $B=200+2\times85=370$ mm. Area provided $=136900$ mm² $>A_{req}$ ✓

$$w=\frac{P}{BL}=\frac{1200\times10^3}{370\times370}=8.77\ \text{N/mm}^2<9.00\ \text{N/mm}^2$$

3. Thickness (cl. 7.4.3.1)

Projections $a=85$ mm and $b=85$ mm (larger and smaller):

$$t_s=\sqrt{\frac{2.5w(a^2-0.3b^2)\gamma_{m0}}{f_y}}=\sqrt{\frac{2.5\times8.77\times(85^2-0.3\times85^2)\times1.10}{250}}=22.08\ \text{mm}$$

It must also be not less than the flange thickness $t_f=15$ mm. Provide $t_s=25$ mm.

4. Connections

• The column end is machined to bear on the plate; connect with a nominal 6 mm fillet weld all round (load is transferred mainly by contact).
• Anchor bolts: 4 nos. M20, embedded about 450 mm with a washer plate (for erection and to resist any uplift).

Answer: base plate 370 × 370 × 25 mm, 4 anchor bolts M20, 6 mm weld, pedestal of M20 concrete.