When sketching a beam system boundary, you can specify the beam direction within the structural beam system. All beams within the beam system will be parallel to the boundary line you select.
Note: Walls and beams curved in plan view cannot be used to define the direction of a beam system.
To specify beam direction
- Select the beam system, and click Mode panel
(Edit Boundary) on the ribbon. - Click Draw panel
(Beam Direction) on the ribbon. - Select from one of the following tools on the Draw panel of the ribbon:
If you select... then... 
(Line) sketch a line, or pick a model line, to define beam direction that is independent of the sketched boundary lines. This line has no other function than to define the direction of the beams in a beam system and therefore cannot be used to close a loop. Select the sketch line to which you want all beams to be parallel. 
(Pick Lines) select the sketch line to which you want all beams to be parallel. 
(Pick Supports) select the beams or structural walls to which you want all beams to be parallel.
The following image shows the selected sketch line and the resulting beam direction.
