Seismic reliability analysis of vertical pumps

This paper deals with the evaluation of cumulative damage of the shaft of the vertical pump subjected to earthquake excitation. First, the friction force between the wearing and the impeller due to the breaking of water film is measured by experimental apparatus. Second, the fluid force between the impeller and the wearing is derived from Bernoulli's equation and is represented by a nonlinear equation containing added mass, added damping and added spring terms. Third, the equation of motion is derived and is integrated by Newmark's β method. Fourth, the torsional moment due to impact is calculated. Then, the maximum shear stress of the shaft is counted by both rain flow method and hysteresis loop method in order to estimate the cumulative damage, and the probability of the failure of the shaft is evaluated. (author)