TY - JOUR

T1 - Cyclic overlay model of p-y curves for laterally loaded monopiles in cohesionless soil

AU - Song, Junnan

AU - Achmus, Martin

N1 - Funding Information: This study was carried out in the scope of the research project “Ho-Pile: Zyklische Erweiterung und experimentelle Validierung eines –-Ansatzes für Sand zur sicheren Monopilebemessung” funded by Bundesministerium für Wirtschaft und Energie (Germany, project no. 0324331A). The authors sincerely acknowledge BMWi support. Funding Information: This research has been supported by the Projektträger Jülich (grant no. 324331A).The publication of this article was funded by the open-access fund of Leibniz Universität Hannover.

PY - 2023/3/8

Y1 - 2023/3/8

N2 - The bearing behaviour of large-diameter monopile foundations for offshore wind turbines under lateral cyclic loads in cohesionless soil is an issue of ongoing research. In practice, mostly the p-y approach is applied in the design of monopiles. Recently, modifications of the original p-y approach for monotonic loading stated in the API regulations have been proposed to account for the special bearing behaviour of large-diameter piles with small length-To-diameter ratios. However, cyclic loading for horizontally loaded piles predominates the serviceability of the offshore wind converters, and the actual number of load cycles cannot be considered by the cyclic p-y approach of the API regulations. This research therefore focuses on the effects of cyclic loading on the p-y curves along the pile shaft and aims to develop a cyclic overlay model to determine the cyclic p-y curves valid for a lateral load with a given number of load cycles. A stiffness degradation method (SDM) is applied in a three-dimensional finite element model to determine the effect of the cyclic loading by degrading the secant soil stiffness according to the magnitude of cyclic loading and number of load cycles based on the results of cyclic triaxial tests. Thereby, the numerical simulation results are used to develop a cyclic overlay model, i.e. an analytical approach to adapt the monotonic (or static) p-y curve to the number of load cycles. The new model is applied to a reference system and compared to the API approach for cyclic loads.

AB - The bearing behaviour of large-diameter monopile foundations for offshore wind turbines under lateral cyclic loads in cohesionless soil is an issue of ongoing research. In practice, mostly the p-y approach is applied in the design of monopiles. Recently, modifications of the original p-y approach for monotonic loading stated in the API regulations have been proposed to account for the special bearing behaviour of large-diameter piles with small length-To-diameter ratios. However, cyclic loading for horizontally loaded piles predominates the serviceability of the offshore wind converters, and the actual number of load cycles cannot be considered by the cyclic p-y approach of the API regulations. This research therefore focuses on the effects of cyclic loading on the p-y curves along the pile shaft and aims to develop a cyclic overlay model to determine the cyclic p-y curves valid for a lateral load with a given number of load cycles. A stiffness degradation method (SDM) is applied in a three-dimensional finite element model to determine the effect of the cyclic loading by degrading the secant soil stiffness according to the magnitude of cyclic loading and number of load cycles based on the results of cyclic triaxial tests. Thereby, the numerical simulation results are used to develop a cyclic overlay model, i.e. an analytical approach to adapt the monotonic (or static) p-y curve to the number of load cycles. The new model is applied to a reference system and compared to the API approach for cyclic loads.

UR - http://www.scopus.com/inward/record.url?scp=85150166744&partnerID=8YFLogxK

U2 - 10.5194/wes-8-327-2023

DO - 10.5194/wes-8-327-2023

M3 - Article

AN - SCOPUS:85150166744

VL - 8

SP - 327

EP - 339

JO - Wind Energy Science

JF - Wind Energy Science

SN - 2366-7443

IS - 3

ER -