Base / support excitation for shell element in nonlinear vibration analysis

[hustzjy312]

Dear all,

Is it possible to do base or support excitation in FEAP83 for shell or solid element in a nonlinear vibration analysis?

Thanks,

Yang

[FEAP_Admin]

Have you looked at section 14.5.4?  or are you interested in something else?

[hustzjy312]

Thanks for your response.

Yes, I have read this section. In this section, it is described to work for linear vibration analysis (modal analysis). But I want to use it for nonlinear vibration analysis, is it possible?

Yang

[Prof. R.L. Taylor]

Can you be more descriptive in what you want to do.

Usually, for non-linear problems the only option is a transient solution using one of the numerical integration schemes in feap (e.g., NEWMARK).  For this you would specify the time-dependent history of the nodes.  Currently, these must be displacements, thus, you would need to have an integrated earth-quake record available if your analysis is seismic. 

Perhaps other users have comments on their experiences.

[hustzjy312]

Hi Prof. Taylor,

Thanks for your reply.

I want to do a nonlinear transient analysis of a cylindrical panel under a uniformly distributed harmonic excitation via the HHT-alpha numerical integrator. Currently, my interest is in applying the equivalent distributed force. In the experiment, a uniformly distributed harmonic excitation is usually applied by a base/ support excitation. Can FEAP83 simulate the equivalent force by specifying a corresponding value of the base acceleration in the command 'base' command as is describe in the manual? 

If FEAP can not do the above stuff, I then need to specify an equivalent uniformly distributed force. If I use shell element, I think that it is equivalent to apply a uniformly surface loading. However, if I use a 3D solid element, is it equivalent to a body force or a surface loading?

Thanks,

Yang

[Prof. R.L. Taylor]

All elements should be subject to an equivalent body force that is harmonic.  For a shell this should include rho*thickness to be a surface loading.