Large-scale experimental studies of two alternate support systems for the seismic restraint of pipin

This is an experimental study of two alternatives to snubbers for the seismic restraint of piping in nuclear power plants. The first alternative is a gap device which allows free thermal movement of the piping across an internal gap and restricts the seismic movement of the piping by impact with the body of the device. The second alternative is a self-centering energy dissipating friction device in which the slip load is proportional to the displacement. Both devices, which are pin-to-pin replacements for the mechanical and hydraulic snubbers currently in use, are much less mechanically complex than snubbers, and their properties can be varied over a wide range.;Extensive earthquake simulator testing was performed on a full-scale piping system restrained by each of the devices. Both devices were tested in numerous configurations. The gap size, gap symmetry, and stiffness were varied for the gap device. The preload, slip force, gap size, and device location were varied for the friction device. For comparison, the piping system was also tested with mechanical snubbers of the type most commonly used in operating nuclear plants.;The effects of the different configurations of the devices on the response of the piping system and the line mounted equipment are presented. The response parameters evaluated include (i) the accelerations, displacements, and stresses in the piping system, (ii) the accelerations of the valves, (iii) the forces and displacements in the devices. The response of the piping system is compared for the snubbers and the alternatives, and the change in frequency content of the responses induced by the snubbers and alternative devices is studied.;Both devices demonstrated their potential as snubber replacements: both can reduce pipe system maintenance and inspection requirements while improving system reliability. The gap device is very simple and would require little maintenance and inspection. The friction device is more complex, hence, it would require a level of maintenance and inspection intermediate between that of the gap device and the existing snubbers. The tradeoff for the increased maintenance is reduced piping response.