Seismic Test and Seismic Response Analysis of U-Shaped Tube Bundle With Triangular Arrays in Steam Generator

Abstract

Ensuring a complete integrity of steam generators’ tubes during earthquakes is critical. So far, excitation tests have been conducted for various square array tube bundles in order to grasp vibration behavior during seismic excitation. A seismic analysis method using a simple model has been developed and subsequently verified by comparing the results against those of the above mentioned tests. In this study, seismic excitation tests were carried out for a U-shaped tube bundle with a triangular close-packed array using a full-scale test specimen as the triangular tube array with thinner anti-vibration bars (AVBs) has different vibration characteristics compared with a squared array one. Natural frequencies, modes and stress distribution in the tube bundle, obtained during the experiment, were applied in order to verify the seismic analysis method through the use of a linear analysis model with all tubes and AVBs connected to each other by linear springs as well as with a nonlinear analysis model with gap elements to simulate contact and sliding between all tubes and AVBs. The vibration displacement of the top of the tube bundle calculated by the linear model were in good agreement with the test result. Stress distribution in the tube array calculated using the nonlinear model were in good agreement with the test result. It has been concluded that the linear and nonlinear analysis models are applicable to seismic analysis including for the case of a U-shaped triangular tube array in a steam generator.