damping

[newman]

In a 3d-model, which type of damping should be select? In maniual examples, damping was None in setting tab, but in some 3d cases in your published seismostruct file, damping was selected based stiffeness. In my model, there is a big different in analytical results for each of damping options (none, based mass, based stiffeness). I don't know which result is correct. I also tested two examples of your verification files by changing the damping option. The results was very different to each other.
I would like to have your explenations about how should be select the best choose for damping type and also how you select the type of damping in your published files (none for sone examples, based stiffeness , ...)?

[huffte]

Hi newman. You are correct in your conclusion that the amount and type of damping employed in structural analysis greatly affects the results.

The appropriate modeling of damping varies from structure to structure, and according to the intent of the analysis.

The answer to your question, in my opinion, must come from you and your supervisor. If there were a single answer which covered all possible scenarios, then there would be no need to accommodate multiple models for damping.

Best of luck, newman.

[seismosoft]

Have also a look at the guidelines in the help file regarding the selection of damping (there is a page specific on Damping). You will find plenty of information there.
Seismosoft Support

[Kirkaguel]

Damping is usually dictated by the Code or Guidelines being used for implementation for example for tall buildings using PEER TBI 2017 or LATBDC 2017 or CTUBH 2017 guidelines all require damping value from 2.5 to 5% but another issue is to select which damping method to choose Rayliegh damping (mass and stiffness proportional) or Modal Damping.

Perform 3D developer is recommending to use modal damping with a very small amount of Rayliegh damping will yield accurate and reliable result. Not sure if this is the same case with Seismostruct though.

[seismosoft]

SeismoStruct supports Rayleigh stiffness proportional and mass proportional damping. Users can set the damping parameters from the project settings in the pre-processor.
Seismosoft Support

[Kirkaguel]

How about modal damping is this possible also in seismostruct?

[seismosoft]

No, modal damping is currently not supported by SeismoStruct.
Seismosoft Support

[obaidullah khan]

According to SStruct user manual pg:188 In nonlinear dynamic analysis, hysteretic damping, which usually is responsible for the dissipation of the majority of energy introduced by the earthquake action, is already implicitly included within the nonlinear fibre model formulation of the inelastic frame elements so if i model my RC structure by using "inelastic force base frame" as an element class type, so according to the SStruct user manual infrmFB is the most accurate and is capable of capturing the inelastic behaviour along the entire length of structural member.so if i adopt this option my whole building will show inelastic behaviour under dynamic loading ...so my question is still i need to define overall damping for my structure, as using this infrmFB does not gives you option of defining any hysteretic curve parameters like Takeda etc and so on................

[huffte]

The nonlinear load displacement behavior adds effective damping. For overall elastic, initial component damping, that is up to the user. There are many different philosophies regarding this initial damping. Some would say the traditional 5% is excessive for nonlinear analysis. Some would say this initial value should be zero in cases where significant inelastic behavior is present. Note also that you have several options in the elastic damping specification, also up to you. Initial stiffness and tangent stiffness damping are available (most would argue that tangent stiffness based is more appropriate). You have the option of Rayleigh, stiffness only, or mass only proportional damping as well.