  In this paper, size-dependent dynamic responses of small-size frames are
modelled by stress-driven nonlocal elasticity and assessed by a consistent
finite-element methodology. Starting from uncoupled axial and bending
differential equations, the exact dynamic stiffness matrix of a two-node
stress-driven nonlocal beam element is evaluated in a closed form. The relevant
global dynamic stiffness matrix of an arbitrarily-shaped small-size frame,
where every member is made of a single element, is built by a standard
finite-element assembly procedure. The Wittrick-Williams algorithm is applied
to calculate natural frequencies and modes. The developed methodology,
exploiting the one conceived for straight beams in [International Journal of
Engineering Science 115, 14-27 (2017)], is suitable for investigating
size-dependent free vibrations of small-size systems of current applicative
interest in Nano-Engineering, such as carbon nanotube networks and
polymer-metal micro-trusses.
