Steel Catenary Risers (SCRs) are still one of the main components in development of oil and gas fields in deep waters. Fatigue design of SCRs in the Touch Down Zone (TDZ) is one of the main engineering challenges in the design of riser systems. Traditionally linear soil models are being used for the riser-soil interaction in the TDZ and they usually lead to very conservative riser design results. Nonlinear riser-soil interaction models have recently been introduced and used in advanced structural analysis of SCRs. Due to hysteretic nonlinear behaviour of the soil, the history of the previous loadings on the soil could change the soil behaviour under the current loading. This paper investigates the effects of the soil nonlinear behaviour on the structural response of SCRs subjected to different loading time histories, defined as series of consecutive wave packets. Sensitivity of the fatigue life of the system, location of the critical node and the maximum stress range to the various wave packet sequences for different soil properties are investigated. The paper concludes that the fatigue life of SCRs is considerably sensitive to the wave packets sequence, and hence the trench development history underneath the risers.
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