Shape and loading imperfection sensitivity of the vibration-correlation technique for buckling analysis of cylindrical shells

A numerical investigation was performed to assess the feasibility of the Vibration Correlation Technique (VCT) to predict the buckling load of cylindrical shells under compression, taking into account shape and loading imperfections. The capability of VCT to provide reliable buckling load predictions using load steps before and after local buckling occurred was also assessed, employing two different VCT procedures and buckling analyses. It was found that the buckling load predictions using VCT are generally insensitive to shape and loading imperfections, but that certain shape imperfections might give unconservative predictions, behaviour which generally can be identified with ease. Increasing the imperfection amplitudes increased the number of secondary buckling events, which in turn decreased the robustness of the VCT to predict the global buckling load when load steps before local buckling occurred were used. Based on numerical results, predicting the global buckling load using load steps after local buckling occurred seemed feasible, but might provide unconservative results. In this case, using a novel empirical VCT procedure and taking into account shape imperfections in the buckling analysis significantly increased the reliability of the VCT predictions. The more conservative outcome of the empirical VCT procedure and the robustness of VCT predictions using load steps after local buckling occurs was also shown to hold true when using experimental data from two cylinders subjected to axial compression.