There are different set damping values based on the type of the structure available in the various codes, but these values are applicable for linear analysis.In order to capture the hysterics damping based on the inelastic behavior of the structure under seismic loading is to calculate the area under the hysteresis curve .The formula you can find in various papers or ATC 40 to be specific

Dear Dr. Shendkar,

you may find useful information on "Displacement-Based Seismic Design of Structures" by Prof. Priestly. There you'll find some useful information and analytical formulation for the evaluation of additional hysteretic damping.

Best regards,

Alessandro Stocchi

Dear Dr. Shendkar,

I usually say that it either is damping or the d-mnd thing.

Differently put - what you are asking is if there is a way to predict something I do not design but rather get for free.

To predict damping you must design the controlling phenomena and know these inside out. If not, you must accept some uncertainty on the matter.

The damping models that are in use are crude and work best for light damping.

Some ramblings of mine on this subject can be found here

http://qringtech.com/2014/06/22/designed-damping-types-mechanisms-application-limitation/

Sincerely

Claes

Hi

I forgot to answer your question regarding methods.

As stated above, our damping models are crude but you can use the Modal Strain Energy method estimate modal damping.

https://www.researchgate.net/publication/228096394_Modal_strain_energy_based_methods_for_the_analysis_of_complex_patterned_free_layer_damped_plates

https://www.google.se/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0ahUKEwjtt6-45MTJAhUi_HIKHROrDBsQFgglMAE&url=http%3A%2F%2Fwww.iitk.ac.in%2Fnicee%2Fwcee%2Farticle%2F0304.pdf&usg=AFQjCNHlmeA8dHq4f1L8E84cy33vvGnrcw&cad=rja

You can insert damping data into FE models and compute complex modes which will give you natrual frequency, mode shape and loss factor.

You can compute frequency response functions and use these to estimate damping.

The above works as long as your material data and the physic of your damping modelling capture the dominant mechnisms. In practice, this implies using a damping material or damper components that add about one order of magnitude more damping than what is given for free.

Sincerely

Claes

Article Modal strain energy based methods for the analysis of comple...

Although there are some typical values for some materials (often with a high uncertainty) that you can use for a theoretical prediction of the behavior of single parts, the damping of structures is mainly dependent of the joints (welded, screwed, bolted, etc.) and this is usually too hard to predict. Since in the joints there are typically more parameters that you can know in advance, global damping is seldom predicted with the desirable accuracy. So, in the end, although you can make an estimate of the damping it is not much more than an educated guess, very dependent of the user experience for the same kind of structures.

That said, the recommended procedure, when feasible, is to build a model with the best damping prediction possible, build a prototype as close to the model as possible and test it to update the damping factor(s) and the other parameters necessary to fit the model to the structure. The updated model is then apt to test minor modifications to adjust it to the specifications with minor discrepancies. Nevertheless, don't be surprised that the damping is the less predictable of the structural parameters.

Rututja,

Really a good fundamental question like your earlier ones.

It is easy to model (calculate) the stiffness (restoring or conservative force ) but very difficult to model the damping (non-conservative force) from physical parameters of the system.

It is possible to predict the damping In those cases only in which we intentionally design and attach the dampers externally e.g. hydraulic dampers in vehicle suspension. In case of structural analysis its impossible to predict damping from physical parameters or becomes highly complicated as we have to go at micro or molecular level.

The following references are recommended as possibly helpful:

Robert F. Steidel, Jr.; "An Introduction to Mechanical Vibrations", 3rd ed, John Wiley & Sons, 1989; cf. Ch. 6.

Ali Hasan Nayfeh, Dean T. Mook, "Nonlinear Oscillations", Wiley-Interscience Series: Pure and Applied Mathematics, John Wiley & Sons, 1979; reprinted ed.: "Wliley Classics Library", 1995; cf. Ch. 3.