HOW TO ASSIGN TIE BEAM IN A BUILDING MODEL?

Hello Everyone,

I noticed that in STAAD Pro when I use to analyze and design a building model all the floor beams at different levels are considered, considering the fact that all the floor beams are at different elevations from the ground level but practically it is not the case as "TIE BEAMS" usually rests on the ground surface and hence usually it is found that in practical case that the beams at the tie level is of smaller dimensions and even the reinforcement provided is quite less in comparison to other floor beams as we all are aware of the fact that tie beams usually carry the wall loads not the floor loads as at tie level usually the floors loads gets transferred to the soil directly and even the tie level beams gets support of the soil directly.

How to assign tie level beams in order to instruct STTAD Pro that this beams are considered as ground beams so as to isolate from the beams of other floor levels?