Aerodynamic Characteristics of Steel Tube Transmission Tower Bodies Under Different Flow Fields

Literature Overview

This paper published in the Journal of Zhejiang University (Engineering Science) in 2019, authored by Bian Rong, Lou Wenjuan, Li Hang, Zhao Xiashuang, and Zhang Ligang, investigates the aerodynamic characteristics of steel tube transmission tower bodies under different flow field conditions. The research is funded by the National Natural Science Foundation of China (Grants 51678525 and 51372515) and the State Grid Corporation of China Headquarters Science and Technology Fund (5211JY17000M). The study focuses on the SZ27102 steel tube transmission tower and conducts wind tunnel tests under both uniform laminar and uniform turbulent flow conditions.

Experimental Methodology

Based on the typical section dimensions at 1/3 height of the SZ27102 steel tube transmission tower body, the researchers designed and fabricated tower body section models with different densities and width-to-height ratios, as well as single-face truss models. High-frequency force measurement wind tunnel tests were conducted under both uniform laminar and uniform turbulent flow conditions.

The key aerodynamic parameters obtained include the single-face truss shape factor, the windward load reduction factor, and the tower body section shape factor. These parameters are critical for the wind load calculation of steel tube transmission towers.

Key Findings and Code Implications

The study reveals that high turbulence intensity inflow conditions lead to a reduction in the single-face truss shape factor and an increase in the windward load reduction factor. As a result, the tower body section shape factors under the two flow conditions are relatively close to each other.

For the single-face steel tube truss shape factor, the values recommended by Chinese codes are generally smaller than the experimental values, and the underestimation is more pronounced when the density is small. The authors suggest that Chinese codes should consider the effect of density on the single-face steel tube truss shape factor and appropriately increase the recommended values.

For the windward load reduction factor, the Chinese code values are larger than both the experimental values and the British code values. The authors recommend partial adjustments to the Chinese code values for steel tube transmission tower windward load reduction factors.

Relevance to Steel Tube Manufacturing and Welding

The aerodynamic performance of steel tube transmission towers is directly influenced by the geometric accuracy and surface quality of the steel tube components:

• Dimensional accuracy: The shape factor is sensitive to the actual cross-sectional dimensions of the steel tubes. Manufacturing tolerances in diameter, wall thickness, and cross-sectional shape can affect the aerodynamic performance.
• Surface roughness: Surface defects such as weld beads, laps, or corrosion can increase the surface roughness, potentially affecting the boundary layer development and the aerodynamic coefficients.
• Joint quality: The quality of welded joints between steel tube members affects the overall structural stiffness and, consequently, the aerodynamic response under wind loading.
• Coating integrity: The surface coating on steel tubes not only provides corrosion protection but also affects the surface roughness. Coating defects can locally increase roughness and alter the aerodynamic characteristics.

Study Insights and Engineering Implications

The research provides valuable aerodynamic data for the wind-resistant design of steel tube transmission towers. The comparison with Chinese and British code values highlights the need for code calibration based on experimental data. Engineers involved in the design of steel tube transmission towers should consider the flow condition (laminar vs. turbulent) when selecting aerodynamic coefficients, as the choice can significantly affect the wind load estimate and, consequently, the structural design.

The finding that the tower body section shape factors under laminar and turbulent flow conditions are relatively close suggests that a single set of aerodynamic coefficients may be acceptable for practical design purposes, provided that the coefficients are appropriately calibrated. However, for critical structures or extreme wind conditions, the distinction between laminar and turbulent flow should be considered.