FATIGUE ANALYSIS OF THE GROUTED CONNECTION OF AN OFFSHORE WIND TURBINE

Resumo

Due to technological advances, Offshore Wind Turbines (OWT) have proven to be a viable
investment alternative in Brazil. However, unlike offshore structures originally developed for the oil
and gas industry, OWT support structures are subject to large bending moments due to the wind and
wave loads on the structure. One of the critical regions of an OWT is the structural connection between
the superstructure and its foundation. This is commonly performed through a cylindrical joint filled with
high-performance grout, made by a metal transition piece that transfers the stresses to foundation
through the grout. The present article aims to evaluate the structural fatigue, under operational and
parked condition, of the grouted connection of a monopile foundation in water depth of 20 meters in
cohesive soil, using SIMA-RIFLEX and TurbSim software. The soil-structure interaction is simulated
applying p-y curves proposed by ANSI / API-RP-2GEO (2011) and DNVGL-ST-0126 (2016). Fatigue
damage is analyzed by applying the Rainflow Counting and S-N curve proposed by DNVGL-ST-C502
(2018) for the grout. It was identified that more severe environmental conditions generate greater
damages, and this behavior is strongly influenced by the rated speed of the turbine and natural frequency
of the structure.