One of the newest features in RSS is Offsets and Rigid Links.  This feature has been in RSS since last year but is not being widely used.  Hopefully the Inside OUT of Offsets will give you the confidence to jump in and use them in your analysis.  (Based on RSS v14.05.03)

Probably more widely thought of  in concrete construction the Offsets command works for  Beams and Columns of material type Steel, Concrete, and Other.  It is also available for Beams designated as Smart Beams.  (Offsets are not available for Steel Joists or Walls.)

Offset Command - How it works

With your framing drawn in a traditional manner- columns on grid lines with beams framing between- specify a distance to move the beam or column and then select the member. 

 

Offset Command - Behind the scenes

Your member was moved in plan and RSS assigned a rigid link connecting the end of the beam with the center of the column. 

 

What is a Rigid Link?

Whether you Google the term or have learned it in a structural analysis course, a Rigid Link is a infinitely stiff element that connects two nodes.  Curiously enough this term is common in FEA analysis and in General FEA programs.  RSS uses a rigid link in the same way a general analysis FEA software (RE, STAAD, competitors) would. 

The Rigid Link connects two nodes that are non-coincident.  Preventing unsupported beam errors and free standing column errors (under one-way deck).  Allowing load transfer between elements and calculation of additional moments due to the eccentricity from the center of the members.

 

Free Form Offset Modeling - How it works

If you prefer to draw the structure in the actual location, ie starting out with unsupported beams, offsets are still possible by manually assigning the rigid links.

With the framing already drawn, select the rigid link command.  Select the end of the beam (or center of the column) and then select the center of the supporting column.

 

How does this affect my analysis?

In the years before the offset command, as engineers we rationalized the resulting moments from any offsets are small enough to be insignificant.  Depending on geometry these extra moments can be large.  Using the offset command will ensure you capture these additional forces.

 

Are there any integration advantages to using Offsets in RSS?

Offsets are fully supported in ISM and are maintained in Revit and AECOsim.  This allows accurate representation of the model in both the BIM  realm and the Analysis realm.

 

Watch Offsets in action as I assign, analyze, review, and integrate.

 

Idiosyncrasies

As with any new tool there are some quirks that we need to get used to. 

  • If the edge of slab was defined as an offset from the member it will move with the member Offset.
  • If you want to change or remove the offset it's easier to delete the member and re-frame.
  • Offsets/Rigid links are assigned to the top of the column on plan only.

 

Don't let projects get you overstressed, RAM gives you strength. 

 

amgh

Anonymous
  • I have a beam that is supported at the end by a wall that is parallel to the beam. When I offset the beam I get a wall free-standing end error. What is the best way to resolve this error?

    Currently, I have deleted the rigid link, added a dummy column at the end of the wall, and a dummy beam running perpendicular from the column to the next line of framing. Is there a cleaner way to resolve my error?