  The ATLAS experiment at the CERN Large Hadron Collider has performed searches
for new, heavy bosons decaying to $WW$, $WZ$ and $ZZ$ final states in multiple
decay channels using 20.3 fb$^{-1}$ of $pp$ collision data at $\sqrt{s} = 8$
TeV. In the current study, the results of these searches are combined to
provide a more stringent test of models predicting heavy resonances with
couplings to vector bosons. Direct searches for a charged diboson resonance
decaying to WZ in the $\ell\nu\ell'\ell'$ ($\ell = \mu, e$) , $\ell\ell q
\bar{q}$, $\ell \nu q \bar{q}$ and fully hadronic final states are combined and
upper limits on the rate of production times branching ratio to the $WZ$ bosons
are compared with predictions of an extended gauge model with a heavy $W'$
boson. In addition, direct searches for a neutral diboson resonance decaying to
$WW$ and $ZZ$ in the $\ell \ell q \bar{q}$, $\ell \nu q \bar{q}$, and fully
hadronic final states are combined and upper limits on the rate of production
times branching ratio to the $WW$ and $ZZ$ bosons are compared with predictions
for a heavy, spin-2 graviton in an extended Randall--Sundrum model where the
Standard Model fields are allowed to propagate in the bulk of the extra
dimension.
