An evaluation of piping system damping by using mockup piping system vibration test data

Japanese BWR nuclear power plant utilities and plant makers had performed a mockup piping system vibration test, aiming at an investigation of the piping system seismic damping ratio under the strong earthquake response vibration with large displacement. The present paper summarizes the mockup vibration test and evaluated results of the natural frequencies and damping ratios. Two mockup piping systems were used in the vibration test, one was made of stainless steel and had 46.5-m. total length with 10-in. diameter, another was also made of stainless steel and had 27.0m. total length with 6-in. diameter. The vibration test was composed of the sinusoidal vibration test and the random vibration test. The present paper mainly describes the sinusoidal vibration test results with regard to the relation between evaluated damping ratio and the maximum response displacement of the piping systems. The evaluated seismic piping system damping values are much greater than the current design criteria.