Wind Vibration Characteristics of Rectangular Steel Tube Concrete Bundle Wind Turbine Towers

Literature Overview

The paper by Gao Xiang, Guo Hongchao, Guo Pinzhang, and Liang Gang from Xi'an University of Technology, published in Earthquake Engineering and Engineering Dynamics (Volume 44, Issue 2, 2024, pages 98-107), investigates the wind-induced vibration response of a novel rectangular steel tube concrete bundle wind turbine tower. This research is supported by multiple funding agencies including the National Natural Science Foundation of China (Grant 51978571) and Shaanxi Provincial Key R&D Programs. The work addresses an emerging challenge in wind energy: extending turbine deployment to lower-wind-speed regions with taller towers and longer blades.

Core Technical Content

The proposed rectangular steel tube concrete bundle tower consists of multiple rectangular CFST sub-tubes bundled together to form the main tower structure. This configuration offers high strength, large stiffness, and strong energy dissipation capacity. The wind-induced vibration analysis employs the Kaimal gust wind speed power spectrum and harmonic synthesis method to simulate wind load time histories, followed by dynamic time-history analysis to compute wind vibration coefficients and equivalent static wind loads.

The results indicate that the tower components exhibit good strength performance with substantial safety margins. The wind vibration coefficient calculated using the gust load factor method based on displacement equivalence is relatively low. The equivalent static wind load obtained from the inertial wind load method produces structural displacements and base shear forces that are consistent with those from stochastic vibration analysis.

Interpretation of Technical Points

The rectangular steel tube concrete bundle concept is innovative because it leverages the advantages of CFST technology while adapting to the geometric requirements of modern wind turbine towers. Rectangular sections are more practical for tower assembly and transportation compared to circular sections, and the bundling approach allows for modular construction. The Kaimal spectrum is widely accepted in wind engineering and provides a reliable basis for simulating turbulent wind loads.

The harmonic synthesis method converts the power spectral density into time-domain wind speed series by summing sinusoidal components with random phases. This approach is computationally straightforward and produces wind time histories that are statistically consistent with the target spectrum. The dynamic time-history analysis then applies these wind loads to the structural model to compute the full response history.

Integration with Engineering Practice

From a steel pipe manufacturing and welding perspective, the rectangular CFST bundle tower presents several practical challenges:

1. Rectangular tube fabrication: Square and rectangular steel tubes require precise roll-forming or welding processes to maintain dimensional accuracy. Out-of-squareness and ovality affect the structural behavior and the fit-up of bundled components.
2. Welding of bundled connections: The interface between bundled sub-tubes requires careful welding design to ensure load transfer and composite action. Longitudinal and transverse welds in the bundle configuration must be designed to resist both bending and torsional stresses.
3. Corrosion protection: Wind turbine towers are exposed to atmospheric corrosion, and the bundled configuration creates crevices that are difficult to protect. Proper surface preparation and coating application are critical.
4. Transportation and erection: The modular nature of the bundle design facilitates transportation, but the welding and bolting details at field joints must be carefully designed to maintain structural continuity.

Study Insights and Reflections

This research is timely given the global trend toward deploying wind turbines in lower-wind-speed regions, which necessitates taller towers and larger rotors. The rectangular CFST bundle concept offers a promising alternative to traditional tubular steel towers, particularly for very tall structures where stiffness becomes a governing design criterion. The validation of the design through dynamic time-history analysis and comparison with equivalent static methods provides confidence in the structural adequacy. For engineers in the steel pipe and structural welding industry, this work highlights the growing demand for specialized steel products in renewable energy infrastructure, and underscores the importance of understanding wind-induced structural dynamics in the design and manufacturing of wind turbine components.