AbstractThe hybrid Chebyshev interval finite-element/statistical energy analysis (CI-FE/SEA) method is proposed as an improved method of mid-frequency response analysis for built-up systems with interval parameters, in which the Chebyshev series approximation theory is incorporated into the hybrid FE/SEA method. In the resultant hybrid CI-FE/SEA model, the uncertainty in the SEA subsystem is modeled by a nonparametric ensemble and dealt with hybrid FE/SEA equations analytically, whereas the uncertainty in the FE subsystem is modeled in terms of interval variables. Truncated Chebyshev series are used to approximate the average energy response and cross-spectrum response of the hybrid interval FE/SEA systems. The bounds of the truncated Chebyshev series with respect to the interval parameters are calculated through use of a Monte Carlo simulation. To compare the proposed hybrid CI-FE/SEA method with the conventional Taylor series based method, the hybrid second-order interval perturbation finite-element/sta...