Estimating the fatigue damage of steel catenary risers in the touchdown zone

[Truncated] One of the most common type of risers to convey fluids between seabed and sea surface in deep water are steel catenary risers (SCRs) as they are a cost effective solution. However, they are highly sensitive to environmental loading, resulting in fatigue issues in the touchdown zone (TDZ).

The fatigue design of SCRs in the TDZ is challenging and suffers mainly from two major drawbacks, as follows:
(i) A high level of uncertainty is present in the fatigue design of SCRs due to
limited understanding of the influence of the large number of parameters on
the structural response of SCRs. These parameters pertain for instance to the
geometry and the structural properties of SCRs, to the environmental loading
and to the seabed characteristics.
(ii) A series of time consuming numerical simulations are usually performed to
assess the stress range occurring in SCRs and deduce the fatigue damage.
This approach is inefficient, particularly for the early stages of design where
optimisation studies are performed to establish values of input parameters
that provide optimal performance.