Beating in Pipes Subject to Shock

Abstract

Often when a pipe is subjected to a shock input in the vertical direction, the pipe will vibrate horizontally after initially vibrating vertically. This vibration is beating that occurs between the vertical and horizontal modes of the pipe. Beating vibration was examined analytically by considering the principal directions of the moment of inertia of the pipe with respect to the shock input direction and by varying the support direction and stiffness at each end of a pipe. Both the moment of inertia and piping supports can produce beating. The conditions needed to initiate this phenomenon are examined and results presented. Two pipe configurations are examined: a cantilever pipe and a pipe supported at each end. In both cases, the effects of varying the principal directions of the moment inertia were examined. The end conditions were varied in the supported pipe. In one case, similar vertical and horizontal supports were specified and in the second two cases vertical supports with two different stiffnesses were analyzed. Beating was found when the end supports were in different directions