Hi Im New to Staad pro Im doing simple steel frame structure analysis. How join L angle(50x505) and square tube at edge by welding joint. I Tried by Start end offset method but im getting error open structure error kindly advise.

Hi Im New to Staad  pro Im doing simple steel frame structure analysis.  How join L angle(50x505) and square tube at edge by welding joint. I Tried by Start end offset method but im getting error open structure error kindly advise.