Nigitha, D.
Behaviour of a large-diameter monopile under two-way lateral cyclic load - Vol.53(2), Apr - USA Springer 2023 - 377-393p.
Large-diameter monopiles are the dominant foundations for the substructure in offshore wind turbine installation. The predominant load such as wind and wave on OWT installed in the offshore environment is cyclic, which affects the soil–pile system's displacement and stiffness characteristics. In the present study, small-scale tests and numerical analyses using PLAXIS 3D were conducted on a single pile embedded in cohesionless soil and subjected to cyclic lateral loading. The effect of load amplitude on displacement and stiffness was investigated by the laboratory model test as well as the numerical analysis of the prototype monopile. From the 1 g model test and the numerical analysis, it was observed that the normalized displacement increases with an increasing number of cycles for a load amplitude ξb = 60% of the ultimate capacity of the monopile. Also, the soil–pile system showed ratcheting behaviour for a load amplitude ξb = 60% of the ultimate capacity. The rate of increase in the accumulated displacement was observed to decrease with an increasing number of cycles due to the densification of sand around the monopile. The serviceability limit state undergoes the shakedown mechanism, while the fatigue limit state undergoes the reversal of accumulated displacement. The change in stiffness was observed to increase with an increasing number of cycles. However, for the two-way loading, the stiffness was observed higher for low load amplitude.
Civil Engineering
Behaviour of a large-diameter monopile under two-way lateral cyclic load - Vol.53(2), Apr - USA Springer 2023 - 377-393p.
Large-diameter monopiles are the dominant foundations for the substructure in offshore wind turbine installation. The predominant load such as wind and wave on OWT installed in the offshore environment is cyclic, which affects the soil–pile system's displacement and stiffness characteristics. In the present study, small-scale tests and numerical analyses using PLAXIS 3D were conducted on a single pile embedded in cohesionless soil and subjected to cyclic lateral loading. The effect of load amplitude on displacement and stiffness was investigated by the laboratory model test as well as the numerical analysis of the prototype monopile. From the 1 g model test and the numerical analysis, it was observed that the normalized displacement increases with an increasing number of cycles for a load amplitude ξb = 60% of the ultimate capacity of the monopile. Also, the soil–pile system showed ratcheting behaviour for a load amplitude ξb = 60% of the ultimate capacity. The rate of increase in the accumulated displacement was observed to decrease with an increasing number of cycles due to the densification of sand around the monopile. The serviceability limit state undergoes the shakedown mechanism, while the fatigue limit state undergoes the reversal of accumulated displacement. The change in stiffness was observed to increase with an increasing number of cycles. However, for the two-way loading, the stiffness was observed higher for low load amplitude.
Civil Engineering