Also called hanger angular deviation in programs like ROHR 2 described as below

• • Consider angular deviation
  • Restoring forces on account of skewing as well as the movement of the support node on a
    circular arc are considered. In addition to the transverse movement, there is a movement
    in direction of the hanger’s anchor in the original hanger direction. To consider the angular
    deviation, the hanger length must be entered. The angular deviation is only considered for
    calculations with non-linear boundary conditions.

Proposed angulation deviation applied as a restoring force and vertical displacement
calculated during the non-linear analysis only at the hanger rod node location.

Y1 = L Cos (theta) where Theta = Sin -1 (X /L). Use the resultant horizontal displacement, X.
W is deadload from GR case

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Example Model: Pendulum1.dat (With large exaggerated seismic movements)
Segment A-no pendulum effect.

Segment B - with pendulum effect.

Examine pendulum effect at Point A10 and assume Hanger Rod = 12” for extreme unrealistic angulation

Calculated Vertical Displacement and Wf-X and Wf-Z horizontal restoring forces for each primary load case

Insert applied support displacements and concentrated forces for GR, T1, E1, W1 cases at point B10

Thermal T1 Fy -1970 Ibf is an additional reaction on the Rod hanger due to the upward arcing movement of the 0.3077" of the Rod Hanger.

After applying these restoring forces and imposed displacements, calculate the new displacements or angle 6. If the new angle is quite different, you may want to repeat the procedure using the new updated angle 6. In many cases you may not need to iterate.
One recommendation, if displacements change by e.g. 50% then iterate.

In the example above there is only a maximum 3% change in the displacements, So will not iterate.

There is neglible change (0.25%) in the thermal stresses which has the pendulum effect. Even with large unrestrained seismic movement only 2.1% change in occ. Stress.