Revit Architecture
Revit StructureYou can use the beam system family to create various beam systems for bays of varying geometry, including arced, polygonal, and cantilevered. The following example provides a method for creating a cantilevered beam system.
Begin with a bay that is similar to the one shown in the following illustration of a partial plan view:

Partial Plan View
Where is it?

Structure panel
Beam System 
Structure panel
Beam System
Beam System panel
Sketch Beam System
Draw panel
(Pick Supports) to select the beam system boundary or
(Pick Lines) to sketch the beam system boundary. 
Pick supports
Mode panel
Finish Edit Mode. The cantilevered beam system displays.

Finished cantilevered beam system