The flow induced vibration occurs frequently in a steam generator in the nuclear power plant. The large-scale steam generator has a large number of tube supports whose cell has rhombus-type shape, and there is a tiny clearance between tube and its support grid. The damping is very complex because of non-linearity and randomness.
The experiment for damping was performed to investigate it with a number of 13 support spans both in air and water environment. The lower part of multi-span fixture was excited by root-mean-square random force with the range of 1∼10 newton to get the frequency response function. The half-power bandwidth method was applied to obtain the damping ratio. The sensitivity of a number of spans was investigated in the range of 9 ∼ 13. In addition, the damping was reviewed from a comparison with Pettigrew [1∼4] and ASME B&PV Code .