Dynamic Behavior of Elastic-Plastic Simply Supported Pipes

Abstract

Nonlinear responses of the dynamic behavior of simply supported pipes were analyzed using a nonlinear finite element program. In the first model, a 1 1/2-in. schedule 40 stainless steel pipe 48 in. long was studied. An elastic-plastic material was specified. The dynamic response of the pipe to a sinusoidal force input was calculated. There was no internal pressure and the magnitude of the force input was held constant as the frequency was varied. A total of 26 cases were studied starting with low frequencies that exhibited static behavior to twice the natural frequency. In addition, a 1-in. straight piping system studied experimentally by Beaney (1985a, b) was modeled analytically. Calculations are compared to experiment. The response of the piping at input frequencies of one-quarter and one-half of the natural frequency exhibited resonance behavior. At one forced frequency, an almost chaotic behavior of the dynamic pipe response was observed. However, at all other specified excitation frequencies, the system reaches a steady-state response. Output in the form of strain and displacement time histories and force displacement plots is developed. In addition, both work and equivalent viscous damping are calculated and presented.