# Steady state dynamics and structural damping

**URL:** <https://prepomax.discourse.group/t/steady-state-dynamics-and-structural-damping/2149>\
**Category:** General Questions\
**Tags:** dynamic\
**Created:** [November 6, 2024, 6:22am UTC](https://prepomax.discourse.group/t/steady-state-dynamics-and-structural-damping/2149 "2024-11-06T06:22:34Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![TKosir](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/tkosir/32/4132_2.png) [@TKosir](https://prepomax.discourse.group/u/TKosir)\
**Post date:** [November 6, 2024, 6:22am UTC](https://prepomax.discourse.group/t/steady-state-dynamics-and-structural-damping/2149/1 "2024-11-06T06:22:34Z")

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Greetings,

When performing steady state dynamics (SSD) using structural damping in the material definition, and damping type “off” in the SSD step the simulations take way longer compared to just using constant damping ratio in the SSD step. Is SSD still using modal super position of structural damping is used instead of viscous damping defined by constant damping ratio?

Thanks!

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**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\
**Post date:** [November 6, 2024, 9:59am UTC](https://prepomax.discourse.group/t/steady-state-dynamics-and-structural-damping/2149/2 "2024-11-06T09:59:22Z")

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SSD supports the following independent forms of damping:

- Rayleigh (global damping parameters) or direct (viscous damping factor for each mode) damping with `*MODAL DAMPING`
- structural (material) damping with `*DAMPING`
- dashpot damping if dashpot elements are used

Disabling damping in SSD step settings only affects `*MODAL DAMPING`, not the material level one.

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<div class="post-metadata">

**Author:** ![TKosir](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/tkosir/32/4132_2.png) [@TKosir](https://prepomax.discourse.group/u/TKosir)\
**Post date:** [November 6, 2024, 1:39pm UTC](https://prepomax.discourse.group/t/steady-state-dynamics-and-structural-damping/2149/3 "2024-11-06T13:39:17Z")

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Thanks for your reply!

In case material structural damping is included, does SSD still use modal superposition, or direct solving of the equations at each frequency?

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<div class="post-metadata">

**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\
**Post date:** [November 6, 2024, 3:16pm UTC](https://prepomax.discourse.group/t/steady-state-dynamics-and-structural-damping/2149/4 "2024-11-06T15:16:33Z")

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SSD in CalculiX is always based on modal superposition (unlike in Abaqus where you can choose direct or subspace based version).