Stress analysis of subsea risers under the combined action of wave force and seismic wave

The operational safety of subsea risers is challenged due to the complex environmental loads such as a current and seismic wave. This paper presents a comprehensive stress analysis of subsea risers under the combined action of wave and seismic waves. Considering the effect of wave and seismic wave load on maximum axial stress and bending stress of subsea risers, the force and the restraint on subsea risers are simplified. The time-dependent wave force on subsea risers is calculated, and the motion equation of subsea risers passing through a strong seismic zone is obtained. Then, the influencing factors of maximum axial stress and bending stress on subsea risers are studied using the finite-element model. The influence of subsea riser stress on shear wave velocity, diameter, wall thickness, bending angle, and properties of subsea soil is investigated. The results exhibit that the maximum stress appears at the elbow of the riser in the combined effect and the axial stress becomes greater than Mises stress. It is observed that the outcome can provide technical support for site construction in a specific area, and it is of great significance for pipe selection and optimization of subsea riser geometry.