Studying the Settlement of OWT Monopile Foundations Using a T-Z Spring with the Torsional Effect

The main purpose of this paper was to study the vertical settlement offshore wind turbine (OWT) monopile support structures, where 5, 10, 15, and 20 MW OWT structures were analyzed under power production, seismic, tropical cyclone loads. Moreover, a t-z spring with shear torsional degrees freedom developed simulate stress along pile soil surface combined effect loads z-direction torsions. This does not require excessive changes finite element program, only known factor is used modify traditional stiffness spring. paper, analyzing several kinds foundations, indicates that resistance may be less than generated by combination torsions, which causes large rotational displacements resulting in failure structures. situation will worse when natural frequency first vertical-direction rotation close integer multiples 3P frequency, cannot well-simulated using springs.