I am trying to model a box type structure made with beams in Staad Pro. The box is fully welded construction with plan bracings and vertical bracings. If I consider the support only at end locations(column locations), it is creating huge tension due to overturning of the box(because of the horizontal loads applied along its height). But in reality the bottom chord is fully welded to the plate on foundation along its length. I want to take advantage of this, considering that box is rigidly connected to the base. Can anyone suggest how to model this support condition in staad( bottom chord rigidly connected to base along its length). Your help in this is greatly appreciated.
Thanks
Sree