An extension is to be designed for I$300$ tension bar. The connection is made by flange and web plates which are connected by $8mm$ thick weld. The material is ST $37,$ and the load case is $H.$ The existing load on the system is $S=20t.$ Determine the minimum plate lengths $L1$ and $L2.$

Flange plates are: PL$\mathrm{.}200\mathrm{.}14$ ; Web plates are : PL$.240\mathrm{.}10$ ; Wled thickness is: $8mm$

For $1300$ :

$F=69\mathrm{.}1c{m}^2$;$h=300mm$;$b=150mm$;

Web thickness $s$ is $t_w=10\mathrm{.}8mm,$ Flange thickness $t2$ is $t_f=16\mathrm{.}2cm,$

$I_x=9800c{m}^4$;$,I_y=451c{m}^4$;$i_x=11\mathrm{.}9cm$;$i_y=2\mathrm{.}56cm$;