Xuehua Li

With the increase in size and flexibility of wind turbines, the safety of large wind turbines becomes a major issue. For this reason, a novel 15-degree-of-freedom (DOF) large wind turbine reduced-order model is proposed in this paper based on the Euler–Lagrange equation. Considering rated speed and parking operating conditions, the dynamic response of the large wind turbine under multidimensional seismic excitation is studied. The 5 MW fixed-bottom wind turbine developed by the National Renewable Energy Laboratory (NREL) is used to testify to the effectiveness of the proposed model. The simulation results indicate that the modal frequencies of the new 15-DOF dimensionality reduction model have a relative error of 0.128–7.820% compared with FAST results, the maximum displacement in the flapwise direction of the blade is 64.93% greater than that in the edgewise direction, and the maximum acceleration is 91.47%. Considering the vertical seismic excitation, the maximum displacement of the edgewise direction is increased by 48.45%, the maximum acceleration of the edgewise direction is increased by 161.17%, the maximum vertical displacement at the top of the tower is within 0.07–0.50% of the horizontal displacement, and the maximum vertical acceleration at the top of the tower is within 5.01–14.42% of the horizontal acceleration. The rated speed state is the worst operating condition in the edgewise direction of the blade, and the maximum blade edgewise acceleration is increased by 180.36% compared with the parking state. The parking state is the worst operating condition in the flapwise direction of the blade, and the maximum blade flapwise acceleration is increased by 365.51% compared with the rated speed state.

As a critical element within the prefabricated structural system, the prefabricated shear wall connected by sleeve grouting is renowned for its superior mechanical performance and high construction efficiency. It is widely applied in mid- and high-rise buildings. However, under fire conditions, not only do the material properties degrade, but the structural connections may also fail, significantly compromising the structural stability and safety. Therefore, this study delves into the fire resistance performance of such prefabricated shear walls. The research primarily focuses on analyzing fire resistance characteristics, including deformation patterns, lateral and axial deformations, fire resistance limits, and other performance metrics, for both prefabricated and cast-in-place shear walls subjected to three hours of single-sided fire exposure. Additionally, a parametric analysis is performed. The results reveal that, after three hours of single-sided fire exposure, the temperature distribution patterns at the mid-width and mid-height sections of the prefabricated shear wall generally resemble those of the cast-in-place wall, displaying arch-shaped and strip-shaped distributions, respectively. However, due to the presence of sleeves, higher temperatures are observed near the sleeve areas in the prefabricated wall, along with a more extensive high-temperature zone. Throughout the three-hour fire exposure, both types of shear walls demonstrated satisfactory structural stability and thermal insulation performance, meeting the requirements for a first-level fire resistance rating (3 h). Nevertheless, greater axial and lateral deformations were noted in the prefabricated shear wall. Key factors influencing the fire resistance performance of the sleeve-connected prefabricated shear wall include the axial compression ratio, longitudinal reinforcement diameter, protective layer thickness, and height-to-thickness ratio. Specifically, axial deformation is found to be directly proportional to the axial compression ratio and height-to-thickness ratio, while inversely proportional to the longitudinal reinforcement diameter and protective layer thickness. Lateral deformation is directly proportional to the axial compression ratio and longitudinal reinforcement diameter, and exhibits a trend of initially increasing and then decreasing with an increase in protective layer thickness, and initially decreasing and then increasing with an increase in the height-to-thickness ratio.