Abstract: Based on the principle of linear superposition,this paper proves generalized Duhamel's integral which reverses moving dynamical load problem to fixed dynamical load problem.Laplace transform and Fourier transform are used to solve patial differential equation of infinite beam.The generalized Duhamel's integral and deflection impulse response function of the beam make it easy for us to obtain final solution of moving line load problem.Deep analyses indicate that the extreme value of dynamic response always lies in the center of the line load and travels with moving load at the same speed.Additionally,the authors also present definition of moving dynamic coefficient which reflects moving.effect.

Key words: generlaized Duhamel's integral, integral transform, infinite beam, dynamic response, moving effect