Simple methods for imperfection sensitivity analysis of caisson skirts under suction installation

Buckling is a critical issue in suction caissons that deserves attention. The probabilistic sensitivity analysis provides a powerful method for characterizing the uncertainty of imperfections, but the previous researches mainly focus on the shell buckling responses, which is difficult to be used directly for the caisson foundation design due to the difference in loading and boundary conditions. Thus, by employing ABAQUS software for finite element analysis, this study proposes a Fourier series-based probabilistic method and investigates buckling behavior under the combined effects of different Fourier coefficients, series types, imperfection magnitudes, and installation depths. The results reveal that the load design values of the three reliability levels decrease with l increasing from 3 to 8. As α/t increases from 1 to 4, the fluctuation of the buckling pressure enhances with a decrease in the overall stiffness of the sample. The half-wave sine Fourier series method captures the imperfection characteristics of caisson foundations with strong constraints at both ends. Imperfection distributions of caisson foundations with strongly constrained tops and open bottoms are represented by the improved half-wave sine Fourier series method through the longitudinal increment of imperfection magnitude. Furthermore, considering the effect of stretching imperfections into the mudline from caisson installation, the numerical analyses using the improved eigenmode method are also conducted. Notably, it shows a more conservative estimate of the buckling load with higher installation depths compared with the probabilistic method, highlighting the importance of such considerations in the caisson buckling design.