Zhuojin Pipe Fitting Co., LtdSelection of Calculation Models for UHV Transmission Line Steel Tube Towers
Literature Overview
This paper by Yang Jingbo, Han Junke, Li Maohua, Li Feng, and Yang Fengli, published in 2010 in the journal Power System Technology (Vol. 34, No. 1, pp. 1–5), addresses the selection of structural calculation models for ultra-high voltage (UHV) transmission line steel tube towers. The research was conducted at the China Electric Power Research Institute and focuses on the 1000 kV Huainan-Shanghai (Anhui Electricity East Delivery) transmission and transformation project, which involves double-circuit UHV steel tube towers on a single tower structure. The study compares three calculation models to determine the most appropriate approach for analyzing the structural behavior of UHV steel tube towers.
Core Technical Approach
The study examines three calculation models for the structural analysis of UHV steel tube towers: the member element model (truss model), the beam-member hybrid element model, and the beam element model. The conventional approach for transmission tower design uses a simplified space truss model with member elements that assume all members carry only axial forces, neglecting bending moments at member ends. The study evaluates whether this simplification is adequate for UHV steel tube towers or whether a more refined model is necessary.
The analysis is performed using two software platforms: a general-purpose tower design program that implements the member element model, and the finite element analysis software ANSYS, which can implement both the beam-member hybrid element model and the beam element model. The comparison focuses on the main material axial forces, tower dynamic characteristics, and main material end moments across the three models.
Technical Parameters and Model Comparison
| Model Type | Element Assumption | Axial Force Accuracy | End Moment Accuracy | Dynamic Characteristics |
|---|---|---|---|---|
| Member element (truss) | Axial force only | Good agreement | Not captured | Good agreement |
| Beam-member hybrid | Axial + bending at ends | Good agreement | Close to beam model | Good agreement |
| Beam element | Full beam behavior | Good agreement | Captured | Good agreement |
The comparison reveals that all three models produce consistent results for the main material axial forces and the tower dynamic characteristics. This indicates that the conventional truss model is adequate for predicting the overall load distribution and dynamic response of UHV steel tube towers. However, the member element model does not capture the end moments in the main materials, which the beam-member hybrid model and the beam element model both predict with close agreement.
Interpretation of Key Findings
The finding that all three models produce consistent axial force and dynamic results validates the conventional truss model approach for the primary structural analysis of UHV steel tube towers. This is reassuring for design engineers who have traditionally relied on truss models for transmission tower design, as it confirms that this approach provides reliable results for the critical design parameters.
The significance of the end moments captured by the beam-member hybrid and beam element models lies in the local design of connections and joints. While the overall tower behavior is well-predicted by the truss model, the end moments in the main materials influence the design of gusset plates, bolted connections, and welded joints. The recommendation to use the beam-member hybrid element model for UHV steel tube tower analysis provides a practical compromise that captures the essential bending behavior without the computational complexity of a full beam element model.
Standards and Design Code Considerations
| Standard/Code | Relevance to Tower Design |
|---|---|
| DL/T 5154 | Design code for 110 kV to 750 kV overhead transmission lines |
| GB 51258 | Code for design of UHV transmission line towers |
| GB 50017 | Steel structure design code |
| GB/T 50011 | Seismic design code for buildings and structures |
The selection of the calculation model has implications for compliance with design codes that specify the structural analysis methods to be used. The recommendation to use the beam-member hybrid element model aligns with the more refined analysis approaches required for UHV towers, which experience higher loads and more complex loading conditions than conventional transmission towers.
Engineering Practice Integration
The practical recommendation from this study is to use the beam-member hybrid element model for the structural analysis of UHV steel tube towers. This model provides accurate predictions of both axial forces and end moments, enabling comprehensive design of both the overall tower structure and the local connection details. The model can be implemented in standard finite element analysis software, making it accessible to design engineers without requiring specialized software development.
For projects involving UHV transmission towers, the implementation of the recommended model requires careful attention to the boundary conditions, load cases, and material properties. The model should be validated against known test data or field measurements where available, and the results should be reviewed by experienced structural engineers to ensure that the analysis assumptions are appropriate for the specific project conditions.
Study Insights and Reflections
This study addresses a fundamental question in structural engineering analysis: the appropriate level of modeling refinement for a given structural system. The finding that the conventional truss model is adequate for overall tower behavior but insufficient for capturing end moments highlights the importance of selecting the appropriate model for the specific design objective. For overall load distribution and dynamic analysis, the simpler model suffices, but for connection design, the more refined model is necessary.
The choice of the beam-member hybrid element model as the recommended approach reflects a practical engineering judgment that balances accuracy with computational efficiency. This model captures the essential bending behavior of the main materials without the full computational cost of a beam element model, making it suitable for routine design work on UHV transmission towers. The study also underscores the importance of validating analysis models against multiple independent approaches to build confidence in the results.
Summary
This literature provides a rigorous comparison of three calculation models for UHV transmission line steel tube towers and recommends the beam-member hybrid element model as the most appropriate approach for structural analysis. The study confirms that the conventional truss model is adequate for overall tower behavior but insufficient for capturing end moments critical to connection design. The recommended model provides accurate predictions of both axial forces and end moments, enabling comprehensive and code-compliant design of UHV transmission towers. This work contributes valuable guidance to the structural engineering community working on high-voltage transmission infrastructure projects.