  We investigate numerically the critical current of two-dimensional fully
frustrated arrays of resistively shunted Josephson junctions at zero
temperature. It is shown that a domino-type mechanism is responsible for the
existence of a critical current lower than the one predicted from the
translationally invariant flux lattice. This domino mechanism is demonstrated
for uniform-current injection as well as for various busbar conditions. It is
also found that inhomogeneities close to the contacts makes it harder for the
domino propagation to start, which increases the critical current towards the
value based on the translational invariance. This domino-type vortex motion can
be observed in experiments as voltage pulses propagating from the contacts
through the array.
