Given

ISMB=350 tf=14.2 bf=140 tw=8.1

ISHB tf=10.6

213.33$\times 10^{3}$Kn Service load

factored load=213.33$\times 10^{3}\times$1.5=320kN

Required - stiffen seated connection

Step I

1. width of seat plate (bf+2sw)

(140+2(10))=160mm

1. thickness of seat plate $\lt$ tr

$\lt$14.2 provide 16mm thick plate

1. bearing length $\frac{R}{twr\times\frac{fy}{ymw}}$=$\frac{320\times 10^{3}}{8.1\times \frac{250}{1.1}}$=173.83mm b-180mm

Step II

Stiffer plate

1. thickness of stiffning plate $\lt$ tw

tsp$\lt$ 8.1

tsp=16mm assume

depth of stiffning plate

$\frac{d}{t}\lt$18.9

d$\lt$18.9$\times$t

d$\lt$18.9$\times$16=302.4

provide depth 300mm

seat plate of size and stiffning plate of size 180$\times$160$\times$ 16

Step III size of weld

Resultant strength = strength of weld

R=$\sqrt{q_{1}^{2}+q_{2}^{2}}$

q$_{1}$=verticle stress /mm=$\frac{320\times 10^{3}}{744\times sw(1mm)}$

q$_{1}$=430.11N/mm

q$_{2}$=Horizontal shear stress/mm=$\frac{m.y}{Iyy}$

m=P.e=310$\times 10^{3}\times (\frac{180}{2})$

y=$\frac{A_{1}y_{1}+A_{2}y_{2}}{A_{1}+A_{2}}$

=$\frac{2(72\times 1)\times 0+2(300\times 1)\times 150}{2(72\times 1)+2(300\times1)}$

$\bar{y}$=120.96mm

Ixx=$(\frac{bh^{3}}{12}+ab^{2})+(\frac{bh^{3}}{12}+Ah^{2})$

[$\frac{2\times 72\times 1^{3}}{12}+2\times(120-96)^{2}]$+$[\frac{2\times 1\times 300^{3}}{12}+2\times 300\times1(150-20.96)^{2}]$

Ixx=7.12$\times 10^{6}mm^{4}$

$q_{2}=\frac{m\times y}{Ixx}$

=$\frac{(28.8\times10^{6})\times120.96}{7.11\times 10^{6}}$

=489.27N/mm

R=$\sqrt{q_{1}^{2}+q_{2}^{2}}$

=$\sqrt{430.11^{2}+489.27^{2}}$

R=651.44N/mm

Resultant strength of weld strength

651.44=leff$\times0.7\times Sw\times\frac{fu}{sqrt{3}.ymw}$

651.44=17$\times0.7\times sw\times\frac{410}{\sqrt{3}\times 1.25}$

651.44=132.55sw

sw=4.91mm$\approx$ 5mm

sw=5mm

Provide cleant angle 100$\times$100$\times$8 connect 4mm fillet weld