A gravity beam framing into a lateral wall may introduce eccentric moments on the wall if the beam is offset from the wall. Similarly, one-way deck may impose eccentric moments on wall. This feature is optional and it is available in RAM Modeler: the command Layout > Walls > Assign Eccentricity can be used to assign eccentricity (offset) information to a lateral wall.

An example is provided in the following figure where a gravity beam is supported by a lateral wall and the beam is offset from the centerline of the wall (the offset distance is marked with "e"). Reaction force in the beam (i.e., ) creates an eccentric moment equal to on the lateral wall.

1. Elevation view of a gravity beam eccentrically supported by a lateral wall
2. Out-of-plane moment created by a gravity beam framing into a lateral wall (plan view)
3. Both in-plane and out-of-plane moments created by the framing gravity beam (plan view)

Eccentric moments on walls

RAM Frame calculates eccentric moments and applies them on wall if eccentricity information is assigned to wall in the modeler. The followings are important to note for a lateral wall with eccentricity assigned:

• The eccentric distance "e" is assumed to be defined as an orthogonal distance to the wall.
• Only gravity beam and one-way deck supported by the wall are considered in calculation of eccentric moments.
• Gravity beam supported by the wall creates an out-of-plane moment on the wall if the beam is orthogonal to the wall. If the beam frames into the wall with an angle, it creates both in-plane and out-of-plane moments subjected to the following conditions:
  • No eccentric moment is considered on the wall if the beam is supported at the end of the wall and the angle between the wall and the beam is larger than 135 degrees.
  • Eccentric moment is always considered if the beam is supported by the wall anywhere on the wall except at its end.
• No eccentric moment is considered from a gravity beam with rigid link offset assigned to avoid duplication of moments.
• No eccentric moment is considered from a gravity stub cantilever to avoid duplication of moments.
• Loads applied directly to the wall (including wall self-weight) do not produce eccentric moment.
• Loads from gravity columns and walls supported by the wall do not produce eccentric moment.
• Two-way decks supported by the wall does not produce eccentric moment.
• Loads in slab edges and slab openings in one-way deck do not produce eccentric moments.

In RAM Frame, the report "Gravity Loads on Frame Member" provide more information about calculated eccentric moments on lateral walls.