Using the Morawetz' Radial Identity, we show that the local energy of a solution is integrable in time and the local L2 norm of the solution approaches zero as time approaches the infinity for a nonlinear beam equation with the spatial dimension > 5.
"Local Time Decay for a Nonlinear Beam Equation." Methods Appl. Anal. 11 (1) 065 - 068, March 2004.