Please need suggestion on extending this strutcure up by 100cm?

[imti7]

Hi Everyone ,

Please reccommend and explain a technique on coloumn cut-lift-join-weld technique to increase gap distance between platforms P1 and P2.

curretnly its 120 cm , i want it to be 220cm in total , so 100cm i will be increasing the 80mm x 80mm x 3mm RHS column heights .
But im stuck by which technique will be good to do it like either extedning with RHS inserts or cut and add footings in between

please find the image below

thanks ,
imtiyaz