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Before posting here I've read couple of articles, some books and through google search for this topic.

I've basic perception of what's the reduction, what's the main goal and how we achieve it. But still got a dangling questions in my mind.

For sake of simplicity let's assume that I've 3 storey building (comprised from columns, beams, and slabs) and I want perform the Guyan reduction for modal anlysis or eigenvalue solution on that.

My point of interest is 2 translational(deltaX,deltaY) and 1 rotational(theta-Z) degreee of

freedom per storey basis. The thing that I dont' understand is: normally columns or beams have 6 DOF per node but in order to conform with overall building DOF (3 ) I should reduce / neglect those DOF's which doesn't conform with storey DOFs. (That is, erasing the columns/rows of corresponding local stiffness/mass matrices)

If the procedure is correct, I'd like to know how we actually keep the the statical consistency?

Those stiffness and mass matrices are derived from statical equations and IMHO can not produce statically correct results by simply omitting them from global equation.

Regards,