Dynamic Wind Response of Ultra-Large Transmission Steel Pipe Towers During Construction

Literature Overview

This 2023 paper by Zhao Jun and colleagues from Jiangsu Power Transmission and Transformation Co., Ltd. and State Grid Jiangsu Electric Power Construction Branch addresses a critical construction-phase safety issue for the Fengcheng-Meili 500 kV Yangtze River Grand Crossing project. Published in the journal Spatial Structures, Volume 29, Issue 4, pages 89–96, the research focuses on the wind-induced dynamic behavior of an ultra-large steel pipe transmission tower reaching 385 m in height, and its coupled system with a double horizontal jib derrick exceeding 400 m during the erection process.

Structural Configuration and Wind Sensitivity

The 500 kV transmission steel pipe tower is a lattice structure composed of steel pipe members, designed for the challenging environment of a Yangtze River grand crossing. The tower height of 385 m places it among the tallest transmission structures globally, making it highly susceptible to wind loading. During construction, the double horizontal jib derrick (抱杆) used for assembly reaches heights exceeding 400 m, creating a coupled structural system where both the partially erected tower and the derrick are exposed to dynamic wind forces simultaneously.

The wind sensitivity arises from several factors: the slender geometry produces low natural frequencies; the large cross-sectional area of pipe members increases drag; and the construction phase introduces temporary asymmetries and incomplete bracing that further reduce structural stiffness.

Finite Element Modeling and Harmonic Superposition Method

The authors established finite element models for both the standalone derrick structure and the coupled tower-derrick system. The harmonic superposition method was employed to simulate wind loading, which decomposes the stochastic wind field into a series of harmonic components and computes the structural response to each component individually before superimposing the results. This approach is well-suited for the frequency-domain analysis of structures with multiple degrees of freedom under turbulent wind excitation.

The wind-induced dynamic response calculations were performed for the single derrick structure and the coupled system separately, enabling direct comparison of dynamic amplification effects. The critical analysis condition was identified as the highest jib assembly stage, where the structural configuration is most vulnerable due to maximum exposure height and incomplete structural continuity.

Comparative Analysis of Anti-Wind Safety Indicators

The study found that the dynamic response of the coupled structure consistently exceeds that of the standalone derrick. This is attributed to the additional mass and stiffness contributions from the partially erected tower, which alter the natural frequencies and mode shapes of the combined system. The interaction between the two structures through shared connection points introduces additional vibration pathways that are not present in isolated analysis.

Wind Vibration Coefficient Comparison with Code Values

The authors calculated the time-history wind vibration coefficients at the highest positions of both the derrick and the tower, and compared these with the values prescribed in the high-rise structure design code. The comparison revealed that the code-specified wind vibration coefficients, which are typically derived for completed structures under service conditions, may be insufficient for the construction phase of ultra-large steel pipe towers. The construction-phase dynamic amplification is more severe due to incomplete structural continuity, temporary bracing configurations, and the presence of the derrick system.

Engineering Practice Implications

This research has direct implications for construction safety planning of ultra-large transmission tower projects. The findings suggest that wind safety assessments during construction should account for the coupled dynamics of the tower-derrick system rather than treating each component independently. Construction methods should incorporate real-time wind monitoring with predefined wind speed thresholds for pausing or resuming assembly operations. Additionally, the temporary bracing and cable systems should be designed based on the amplified dynamic response values rather than static or isolated dynamic analysis results.

Key Reflections

The study exemplifies the importance of construction-phase structural analysis, which is often underemphasized relative to service-phase design. For ultra-large steel pipe towers, the construction phase may represent the most critical loading condition due to incomplete structural systems and the presence of temporary equipment. The coupled system analysis approach adopted here should become standard practice for similar projects. The results also highlight the need for updated design guidelines that specifically address the wind engineering of construction-phase structures, particularly for steel pipe lattice towers exceeding 300 m in height.