Reference (Wang and Lin 2001) studied the random
responses of shear-type muti-degree of freedom (MDOF) hysteretic system by utilizing pseudo excitation
method (PEM) and equivalent linearization method (ELM). Reference (Du et al. 2006) extended this
method to analyze the responses of base-isolated structures under stationary random excitation; however,
it was found that the flexural effect cannot be neglected when the ratio of height to width of the
superstructure exceeds 4.