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{{Test Problem
| name = Pendulum |
| description = Modeling of pendulum in SAP2000 using time history with large displacements |
| keyword = large displacements; pendulum; contact problem |
| program = SAP2000 |
| version = all |
| status = in progress |
| type = test problem |
| id = ok/pendulum (by bm)}} |


You can solve pendulum problems in SAP2000 by performing nonlinear time-history analysis with large deflections.

If you are trying to solve typical structural problems with a pendulum used for isolation or as a tuned-mass damper, this is usually represented by using a linear spring to represent the restoring force. For a pendulum, this could be either be a torsional spring at the support, or a horizontal spring, attached to the bottom.

h1. Screenshots

The screenshots below and the attached video show modeling of set of pendulums hitting each other (so called [Newton's cradle|http://en.wikipedia.org/wiki/Newton%27s_cradle]). The contact was modeled using [gap links|kb:Gap link property] connecting each adjacent pair of balls. However, because the rods were axially stiff, the gaps contacted nicely.

!Pendulum_1.png!

!Pendulum_2.png!

h1. See Also

* [kb:Contact surface problem]

h1. Attachments

* [Pendulum video|^PendulumPendulum^Pendulum_video.zip] (Zipped AVI file, 0.3 MB)

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*To do:* Upload model for test problem with pendulum (by Rob).
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