Abstract
The study investigated the influence of correlations between random variables on the reliability index of selected structural systems. The structural design parameters were defined as deterministic quantities and random variables, and the correlation between them was modeled using four correlation-matrix variants. The ultimate limit state was adopted as the safety criterion, and appropriate limit state functions were formulated to identify structural failure. A sensitivity analysis of the reliability index with respect to the random variables was carried out using the Hasofer-Lind reliability index as the performance measure. The First-Order Reliability Method served as the primary computational approach, with Monte Carlo simulation as the reference method. All calculations were performed using the NUMPRESS Explore. The analyses demonstrated that increasing the correlation coefficient leads to higher values of the reliability index. The results confirm that the correlation coefficient significantly affects the reliability assessment and should not be neglected in structural safety evaluations.