How to model pendulum swing of a pipe on a rod support in AutoPIPE?
Description: Rod Hanger Pendulum or Angulation ModelingProduct: AutoPIPEVersion number: V8i (v9.1)Submitted by: MU
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.
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 exaggerate B – with pendulum effect for extreme unrealistic angulation
Calculated Vertical Displacement and Wf-Z horizontal restoring forces for each primary
Insert applied support displacement and concentrated forces for Gr, T1, E1, and W1 at B10
Thermal T1 Fy = -1970 ;bf is an additional reaction on the Rod hanger due to the upward arcing moment of the 0.3077" of the Rod Hanger.
After applying these restoring forces and imposed displacements, calculate the new displacements for angle Theta. If the new angle is quite different, you may want to repeat the procedure using the new updated angle Theta. 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, thus no iteration in necessary.
There is negligible change (0.25%) in the thermal stresses which has the pendulum effect. Even with large unrestrained seismic movement only 2.1% change in Occasional Stress.
Select the following link to download the Excel data sheet and AutoPIPE model used in the example
https://communities.bentley.com/products/pipe_stress_analysis/m/pipe_stress_analysis_gallery/269648.aspx
Bentley AutoPIPE