This article deals with introducing a closed-form solution for considering the
vibration of macro-micro-nano plates and shells made of unit material with
functionally graded porosity (FGP). Classic continuum theory beside modified
nonlocal strain gradient theory are used at macro and micro/nano scales,
respectively. The governing equations are obtained in the frame work of third
order plate and shell theories. In the solution procedure, a differential operator
is defined and by using it, five equations of motion are converted to the
five algebraic equations. Then, by satisfying the equations of boundary conditions
and achieving the nonzero solution, the frequencies are extracted.