“…Recently, an interval perturbation method, based on perturbation theory and interval operations, was proposed. By combining this method with the finite element method, the interval perturbation method has been applied in a wide variety of engineering uncertainty problems (Qiu and Elishakoff, 1998;Zhang et al, 2007;Impollonia and Muscolino, 2011;Fujita and Takewaki, 2011;Chen et al, 2003;Yu, 2012, 2013;Xia et al, 2013a). A common shortcoming of the interval methods is that the probability density functions within the response confidence intervals are missing.…”