Pressure effects on the static response of offshore tubular connections

The paper focuses on the influence of external hydrostatic pressure on the ultimate capacity of uniplanar X and T welded tubular connections under axial and bending loads. Nonlinear finite element tools, calibrated through available experimental data, are employed to simulate the tubular joints. The numerical results are presented in the form of load-displacement (or moment-rotation) equilibrium paths for different pressure levels, as well as in the form of pressure-load interaction diagrams. It is shown that external pressure causes structural instability, and has significant effects on both the ultimate load and the deformation capacity of the joint. The effects of external pressure on an X joint under balanced axial load are demonstrated and explained qualitatively using a simplified elastic–plastic mechanical model, which describes joint behavior through closed-form expressions.