Response of a piping system under seismic and thermal loading

The report presents the results of an investigation into the behavior of a complex spatial piping system under simulated seismic and thermal loading. The control of seismic response by steel energy absorbing devices is studied and compared with equivalent response controlled by shock arrestors. The specimen selected for study was a half-scale model of a piping system from a nuclear reactor power plant. This was tested in its original design configuration using mechanical shock arrestors (snubbers), and subsequently in a revised configuration using ductile steel energy absorber. The influence of the snubbers and of different energy absorbers on the dynamic response of the pipe system is discussed. A direct one-to-one replacement of the snubbers by energy absorbers allows a direct comparison of the results. The response of the structure was studied under all three direction components of ground motions, though a maximum of two components (one horizontal and the vertical) was applied simultaneously. In the case of the energy absorbers, the effect of a thermal loading was simulated by deforming the system at the restrainers, and the seismic loading was superimposed on this biased configuration. Over a hundred test runs were recorded using four different artificial earthquakes as well as sinusoidal input. A study of damping behavior, frequency spectra and hysteresis loops for both shock arrestors and energy absorbers facilitates an extensive interpretation of the experimental data. (orig./HP)