A stochastic averaging method is proposed to predict approximately the
response of multi-degree-of-freedom quasi-nonintegrable-Hamiltonian s
ystems (nonintegrable Hamiltonian systems with lightly linear and (or)
nonlinear dampings and subject to weakly external and (or)parametric
excitations of Gaussian white noises). According to the present method
, a one-dimensional approximate Fokker-Planck-Kolmogorov equation for
the transition probability density of the Hamiltonian cart be construc
ted and the probability density and statistics of the stationary respo
nse of the system can be readily obtained. The method is compared with
the equivalent nonlinear system method for stochastically excited and
dissipated nonintegrable Hamiltonian systems and extended to a more g
eneral class of systems. An example is given to illustrate the applica
tion and validity of the present method and the consistency of the pre
sent method and the equivalent nonlinear system method.