Dynamical simulations and scaling arguments are used to study the
current-voltage (IV) characteristics of a two-dimensional model of resistively
shunted Josephson-junction arrays in presence of percolative disorder, at zero
external field. Two different limits of the Josephson-coupling concentration
p are considered, where pc is the percolation threshold. For p>pc
and zero temperature, the IV curves show power-law behavior above a disorder
dependent critical current. The power-law behavior and critical exponents are
consistent with a simple scaling analysis. At pc and finite temperature T,
the results show the scaling behavior of a T=0 superconducting transition. The
resistance is linear but vanishes for decreasing T with an apparent
exponential behavior. Crossover to non-linearity appears at currents
proportional to , with a thermal-correlation length exponent
νT consistent with the corresponding value for the diluted XY model at
pc.Comment: Revtex, 9 postscript pages, to appear in Phys. Rev.