modal transient analysis

gopal_rathore

Hi,

I am working on shock response transient analysis using modal superposition method.

 

As this requires a pre-requisite of solving normal modes analysis . I wanted to know how many modes to be captured for transient run.

 

Does this depend on effective mass ratio or on participation factor?

 

Or are there any thumb rules or guidelines for the same

 

My shock response analysis is for 30 ms

 

Thank you

Pranav Hari

Hi gopal_rathore

 

According to the e-book 'Dynamic Analysis with OptiStruct' there are no such thumb rules. The natural frequencies and normal modes of a structure can be a function of the load and the damping present on the system.  A system with N DOFs will have N natural frequencies.

 

Have a look at the e-book (page 77)  modal transient analysis is described in detail with a tutorial.

https://altairuniversity.com/free-ebook-learn-dynamic-analysis-with-altair-optistruct/