PSI - Issue 78

Ettore Sorge et al. / Procedia Structural Integrity 78 (2026) 1863–1870

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aerodynamic and seismic excitations, underscoring the intricate dynamic interplay that governs structural integrity when these environmental demands act in tandem.

Table 1. WTG Properties (NREL 5-MW).

Properties

Number of blades

3

Rotor, Hub Diameter

126,3 m

Cut-in/rated/cut-out wind speed

3/11.4/25 m/s 6.9/12.1 rpm

Hub Height

90 m

Cut-in/rated rotor speed

Tower top diameter Tower base diameter Thickness bottom

3.87 m 6.00 m 27 mm 19 mm

Rotor Mass Nacelle Mass Tower Mass

110 Mg 240 Mg 347 Mg

Thickness top

3.1. Wind load (W) Wind-load characterization for the WTG-HSFD system followed the framework introduced by (Sorge et al., 2024); however, the present study broadened the aerodynamic demand by imposing seven independent turbulent wind realizations at the rated operating condition ( ℎ =11.4 ⁄ ) . These records, representing the regime that generates the peak thrust force, were synthesized with QBlade (Marten, 2020) in accordance with (IEC 61400-1, 2009). The resulting time histories of hub-height velocity, rotor thrust, and overturning moment — illustrated in Figure 2(a – c) — were subsequently superimposed on the seismic input to formulate the coupled load combinations. Emphasis was placed on the rated scenario because previous investigations demonstrated that thrust-induced structural demands under cut-out winds ( ≥ 25 ⁄ ) are comparatively lower (Avossa et al., 2017). It is worth mentioning that once the 25 ⁄ threshold is exceeded by the turbine pitches its eight-section blades — whose maximum chord is 4.652 m — toward a feathered position (pitch ≈ 90°) to avert damage, whereas during normal operation the pitch angle varies between 0° and 23.45° to sustain aerodynamic efficiency while preventing overloads. Figure. 2 shows the envelope of the wind velocity signals generated at hub height using QBlade, along with the computed thrust forces over time, and Case 1 is highlighted in blue. These signals are applied at the nacelle node and used as aerodynamic input in the structural model to represent the rated wind operating condition during combined loading scenarios.

(a)

(b)

(c)

Figure 2. Wind speed, thrust at the hub, and moment at the hub in rated scenario: (a) wind velocity, (b) thrust and (c) moment.