“…Due to the necessity and importance of treating the aleatory and epistemic uncertainties properly with corresponding mathematical methods rather than simply using the traditional probabilistic methods to treat all the uncertainties as random ones under strong assumptions (Der Kiureghian and Ditlevsen 2009), there emerges increasing literature in recent years to address the reliability analysis problems under both aleatory and epistemic uncertainties, e.g. Fuzzy set theory (Zhang and Huang 2010;Li et al 2014;He et al 2015), random set theory (Oberguggenberger 2015) and probabilistic bounding analysis (Sentz and Ferson 2011), combined probabilistic and interval analysis method (Jiang et al 2013), combined probabilistic and evidence theory method (Du 2008;Eldred et al 2011;Yao et al 2013b), and other numerical approaches such as doubleloop Monte-Carlo Simulation (MCS) (Du et al 2009), perturbation based method (Gao et al 2010(Gao et al , 2011, encapsulation based method (Jakeman et al 2010;Chen et al 2013), families of Johnson distributions based probabilistic method (Urbina et al 2011;Zaman et al 2011), etc. Among these researches, one of the widely used methods is to model the epistemic uncertainties with intervals and generally the interval bounds are fixed.…”