nodal mass for eigen analysis

[saharnaz]

i have a 3d Rc moment frame in etabs(7 story &two bays). but i've modeled a 2d frame in opensees (and using buckling restrained braces in it). now i want to calculate the natural period before and after using BRBs.
should i consider live loads on the compute of nodal mass?
which combination of load should i use?

[jackjo]

Hi saharnaz
For nodal mass, you should consider all loads applied on beams and divide them to related nodes. for considering live load, if applied distribute load on beam be W, W means:
W=WD+0.2WL that WD is dead load and WL is live load. 0.2 is live load participation Percent.

[saharnaz]

thanks for your help