Structural monitoring of a wind turbine steel tower - Part II: monitoring results

Repowering Steel Tubular Wind Turbine Towers Enhancing them by Internal Stiffening Rings

“…where for air density, ρ is equal to 1.25 kg/m 3 , for wind speed, v is expressed in m/s, and for the wind pressure, p is in N/m 2 . According to Rebelo et al [28,29], the magnitude of the average maximum bending moment at the base of the tower under monitoring is 2.9×10 7 N•m. The self-weight of the tower was calculated by the software, based on the dimensions of the tower and the material density.…”

“…The numerical models were developed using the commercial package ABAQUS. The models were first validated with respect to existing data recently obtained by Rebelo et al [28,29] who monitored the structural response of an actual wind turbine tower of 76.15 m height.…”

“…The self-weight of the wind turbine, a bending moment created by the gravity of wind turbine with an eccentricity and a horizontal wind load applied on the blades of the towers can be simply applied to the reference node. The horizontal force is 380 kN according to the inventory data of Rebelo et al [28,29]. A non-linear static analysis has been performed to solve the numerical model.…”

“…As previously mentioned, the tower, which was studied by Rebelo et al [28,29], was monitored by sensors placed at four different levels. The measured stress at each level was compared with the numerical results of the present model.…”

“…In this paper, a repowering solution with reference to the design of wind turbine towers is numerically performed by means of the finite element software ABAQUS [27]. Firstly, the results of the numerical model are compared with the experimental data obtained by Rebelo et al [28,29]. Secondly, to repower wind turbine towers in a more efficient way, the wall thickness (referred to as "T"), the mid-section width-to-thickness ratio of the ring sections (referred to as "R") and the spacing of the stiffening rings (referred to as "H") are considered as the repowering design variables for each height case of 50 m, 150 m and 250 m. To obtain a direct comparison, the maximum von Mises stresses and horizontal sways of the finite element model towers are calculated for each height case.…”