Reliability study of suction caissons for catenary and taut-leg mooring systems

• Failure criteria for suction caissons considering the line angle at padeye.
• Probability distributions of capacity as a function of length and length–diameter ratio.
• Reliability analyses considering both line tensions and capacity at the mudline.
• Failure probabilities expressed as a function of caisson length.
• Safety factors calibration performed separately for caissons with catenary and taut-leg moorings.

A detailed study on the reliability of suction caissons for moorings of floating systems is presented. Reliability analyses are performed considering mooring line tensions and suction caisson capacity at the mudline. The probabilistic modeling of caisson capacities is based on simulations using a plastic limit model calibrated to numerical computations using finite element modeling. Loading for catenary and taut-leg mooring systems were considered for the reliability analyses; loads were expressed as functions of uncertain metocean variables by means of response surfaces. Reliability analyses were carried using FORM. Linear relationships were established between the logarithm of failure probability and caisson length for both cases of mooring systems. Partial safety factors for capacity, and mean and dynamic line tensions were calibrated separately for caissons in connection to catenary and taut-leg moorings.