Hip roofs often include a setback for the hip girder truss. By splitting the roof into these simplified rectangular plates, you can analyze the hip girder's load path and reactions, even though LAVA doesn’t support angled or polygonal plates directly. This approach helps you capture the main load paths, design your girder, and jack trusses with reasonable accuracy.
In this example, the hip truss girder is set back approximately 8 feet from the building corner, creating a shorter span for the jack trusses and reducing reactions at the outer walls.
Modeling this in LAVA
LAVA’s layout tools are based on rectangular plates, which don’t allow for direct modeling of the setback along a diagonal plane. To approximate this hip setback condition:
Define the hip girder plane as a rectangular plate at the 8 ft setback location.
Model this as its own plate, representing the area supported by the hip girder.
The jack trusses can be simplified as framing perpendicular into the girder plate.
Frame the remaining roof area with additional rectangular plates laid out horizontally behind the girder setback.
These plates represent the rest of the roof planes, framed back to the ridge or supported by interior walls.
Draw in the Truss Girder as a representative beam
This is to pick up the loads from the hip and send them towards the outer walls as point loads.
This is just a placeholder for the truss girder so it’s been renamed to indicate it’s not designed in LAVA.
Adjust loads accordingly:
Check girder reactions to ensure loads are approximated realistically.
Add any additional roof loads to the plate so that tributary areas match what the girder accurately carries.
Note: The truss girder is a representation using a Beam. You can change the Beam Name to make this clear. If you do not want to include the truss girder design in the Report, uncheck “Print in Report”.
