Question about modal analysis of the talll building

[gooddaytogo]

Hello everyone:

I am trying to build a model of a tall frame building to carry out the mosal analysis, and I use the command below to define the mass density of the beam:

element nonlinearBeamColumn 1 1 2 7 1 1 -mass 0.86;

The ''-mass 0.86'' includes the Self Weight of the beam, Slab Dead Loads and Superposed Dead Loads.

My question is during the modal analysis process, you need to apply the Dead Loads and Live Loads to the building, how does the OpenSEES deal with the mass density ''-mass 0.86'' ? Does it ccalculate the Dead Loads from "element nonlinearBeamColumn 1 1 2 7 1 1 -mass 0.86;" automatically or should I apply the Dead Loads again when I apply the loads?

Thanks.

[selimgunay]

In Opensees, there is no relation between the vertical forces that you apply to the structure in gravity analysis and the masses that are used for the eigenvalue analysis. You should explicitly input all the necessary masses

[gooddaytogo]

So can I interpret it in this way that the ''-mass 0.86'' in the command, element nonlinearBeamColumn 1 1 2 7 1 1 -mass 0.86, will only be used in the modal analysis (eigenvalue analysis), and when you want to apply the dead load to the model using load pattern command, even ''-mass 0.86'' includes the dead load, it will not affect the dead load you applied to the building, so they are two independent process? Thanks.

[selimgunay]

Yes they are two independent processes. "-mass 0.86" is not used in gravity analysis.

[gooddaytogo]

What if I do the static analysis and transient analysis? Will ''-mass 0.86'' be regarded as the dead load or should I define the dead load again by using load pattern command.

Also if I didn't turn the PDelta effect and didn't define the dead load by using load pattern command when doing the transient analysis, will the results be different? Thanks.