Comparative in-situ testing of dynamic pipe supports

As part of the earthquake investigations at the HDR test facility (a decommissioned nuclear power plant in the FRG) a comparative study of dynamic pipe support systems was performed. In these tests, the reactor building was excited by means of a large eccentric mass shaker with forces up to 10 MN. Thus, the floor response spectra from test loading were comparable to a SSE design spectrum. Five different support systems of a branched pipe loop with diameters from 100 to 250 mm were tested in 3 runs each: - a typical stiff US support system, consisting of 6 rigid restraints and 6 snubbers, designed by INEL for US-NRC, office of research - a more flexible system with 5 rigid restraints, designed by KWU for KfK - a very flexible system with only 2 rigid restraints, for which no design calculations were performed - two systems based on the US-NRC system, but with replacement of snubbers by - energy absorbers from Bechtel - seismic stops from Cloud both designed under contract with EPRI. Tho ugh the analyses of test data are not all completed, the statement is possible, that the stiff US support system did not reduce the dynamic pipe stresses, accelerations or forces in restraints compared to the more flexible KWU support system. Regarding the test results from snubber replacements, both types seem to be useful alternatives, provided that reliable linear mathematical models of these nonlinear elements are available for design calculation