Bounds on structural system reliability in the presence of interval variables

The failure of a structural system is usually governed by multiple failure criteria, all of which are to be taken into consideration for reliability estimation. If all the uncertain parameters are defined as random variables, then the system reliability can be estimated accurately by using existing techniques. However, when modeling variables with limited information as intervals with upper and lower bounds, the entire range of these bounds should be explored while estimating the system reliability. The computational cost involved in estimating reliability bounds increases tremendously because a single reliability analysis, which is a computationally expensive procedure, is needed for each configuration of the interval variables. To reduce the computational cost involved, high quality function approximations for individual failure functions and the joint failure surface are considered in this paper. The accuracy and efficiency of the proposed technique are demonstrated with numerical examples.