January 10, 2019
Modeling Hanger Columns in RISAFloor
A floating or hanger column is a vertical member that is supported above by a transfer beam and consequently doesn’t transfer its load directly to the foundation. This type of construction is widely used in multi-story commercial and residential buildings because it allows for the column layout on individual floors to be modified where larger, open spaces are required by the building’s program. Although these types of members are not explicitly supported, they can be easily created in RISAFloor.
The way to do this is by modeling them as lateral columns in RISAFloor with gravity columns below. The gravity columns will act as a dummy support member in RISAFloor but will be omitted in RISA-3D. Additionally, the beams supporting the hanger columns from above as well as said beams need to be designated as “lateral” as well in order for them to be available in RISA-3D.
You can then solve the model in RISAFloor and the loading will be incorrect (because of the dummy gravity columns) but once you export to RISA-3D only the lateral members will be exported. As a result, you will have the correct geometry. Once in RISA-3D, simply re-solve the gravity load combinations to finalize the hanger design.