Abstract
Buckling is a critical mode of failure that governs the design of thin-walled shell structures. The buckling load of shells is sensitive to geometric imperfections, the effect of boundary conditions, or eccentricity in the load application path. Non-destructive evaluation techniques are widely used for estimating the buckling load of structures. Force-stiffness (F-s) technique is one such method used for the estimation of buckling load without subjecting the structure to failure. This paper focuses on the evaluation of the buckling load of oblate ellipsoidal shell structures subjected to external pressure using the F-s technique. Experiments are carried out on scaled ellipsoidal shells fabricated using steel with similar R/t values. The experiments are performed on five domes until buckling and the strains under pressure loading are measured using strain gages. Graphs of the pressure-to-strain ratio versus applied pressure are plotted for the five scaled-down domes. It is observed from these plots that the F-s technique can predict the buckling load with 95% accuracy in all the scaled-down domes using strain data up to 80% of the buckling load. All the domes buckled within a range of 2.8 to 3.5 MPa. With this confidence, the F-s technique is applied for buckling load prediction of a large-scale dome structure, almost 3 times the size of the scaled-down dome, subjected to external pressurization. Furthermore, the application of the F-s technique numerically to predict the buckling load of oblate shells is also explored.
