This report deals with the effect of damping on evaluation expectation of linear cumulative damage factor from ductility factor and cumulative ductility factor. In the evaluation of the linear cumulative damage factor, wave number and the probabilistic distribution of peak amplitudes are required. The wave number is evaluated referring to the closed form equation developed by Matsushima (1992)5). The probabilistic distribution of peak amplitudes is inferred from the displacements of center of oscillation per cycle. The displacement of center of oscillation is considered to follow the gamma distribution. The expectation of linear cumulative damage factor is given by single stochastic integral.
