Consistent element treatment of Rayleigh damping with flags

[dborello]

Currently different elements default to Rayleigh damping on or off. For example, truss elements by default will be excluded from Rayleigh damping while elastic beam columns will be included.

It would likely reducing modeling error if all elements defaulted to the same behavior (perhaps off by default). Furthermore, it would be extremely useful to provide a doRayleigh flag for all elements.

My motivation for this comes from modeling beam depths using stiff elastic beam columns. From the documentation, it is not obvious that they are included in Rayleigh damping. However, they can not be excluded from damping calculations.

Thanks,
Dan

[fmk]

we decided we must keep OpenSees backward compatible when we added damping to the Truss element .. historically Trusses did not use the Rayleigh damping factors because it was envisioned that the users would use the Truss with viscous materials.

it's again a matter of backward compatability

damping can be turned off in elements at the moment by making use of the region command.

i do take your point about the inconsistancies.

[dborello]

I found the region command, that seems to work well.

I can appreciate maintaining backwards compatibility. I doubt many users double check their results are still valid when upgrading.

Perhaps it can be added to a list of items to be fixed for a release not guaranteeing backwards compatibility (3.0?). I know the inconsistencies have tripped up several people.

Thanks,
Dan