Wind Vibration Control of 1000kV Steel Pipe Towers A Literature Study Note

Engineering Background and Challenge

The paper by Yang Jingbo, Han Junke, Hua Xugang, and Chen Zhengqing (China Electric Power Research Institute and Hunan University, 2010) addresses the wind-induced vibration control of 1000kV steel pipe towers used in the Huainan-Shanghai ultra-high voltage transmission project. This is a landmark engineering challenge because the 1000kV transmission towers are significantly taller and more slender than conventional towers, making them highly susceptible to wind-induced vibrations. The research was supported by the National Natural Science Foundation of China (Grant 50808079).

Types of Wind-Induced Vibration

The study identifies two distinct types of wind-induced vibration that require separate control strategies:

Vibration Type	Location	Mechanism	Control Method
Global bending vibration	Entire tower	Aerodynamic buffeting and vortex shedding	Viscoelastic dampers on main members
Global torsional vibration	Entire tower	Asymmetric wind loading	Tuned mass dampers at cross-arm ends
Local vortex-induced vibration	Individual tube members	Vortex shedding at critical wind speeds	Helical flow disruption strips

Control Strategy Details

Viscoelastic Damper for Bending Vibration

Viscoelastic dampers are installed in parallel with the main steel pipe members of the tower to control bending vibrations. The key design parameters include:

Damper size and stiffness, calibrated to the tower's fundamental bending frequency
Temperature-dependent viscoelastic properties, which must be characterized over the expected service temperature range
Mounting arrangement that ensures effective load transfer between the damper and the tower structure

Tuned Mass Damper for Torsional Vibration

Tuned mass dampers (TMDs) are placed at the ends of the cross-arms to control torsional vibrations. The TMD parameters are tuned to the tower's fundamental torsional frequency, and the damping ratio is optimized to provide effective vibration reduction.

Helical Flow Disruption Strips for Local Vibration

For the local crosswind vortex-induced vibration of individual steel pipe members, helical flow disruption strips are proposed. These strips modify the aerodynamic characteristics of the tube members by disrupting the coherent vortex formation, thereby reducing the amplitude of vortex-induced oscillations. The helix angle, pitch, and number of strips are critical design parameters.

Control Effectiveness

The research demonstrates that the proposed combined control strategy can achieve the following performance improvements:

Response Parameter	Reduction Level
Tower top downwind displacement	Up to 30%
Tower top downwind acceleration	Up to 30%
Member crosswind vibration	Essentially eliminated

Steel Pipe Manufacturing and Welding Considerations

From a steel pipe engineering perspective, the implementation of wind vibration control measures introduces several fabrication challenges:

Damper Attachment Welding

The viscoelastic dampers and TMDs must be securely attached to the steel pipe tower members. The welding of damper mounting brackets to the main pipe members requires careful attention to:

Weld location selection to avoid stress concentration zones
Weld procedure qualification for the specific steel grade and thickness used in the tower members
Post-weld inspection including UT and MT to verify weld integrity
Residual stress management to prevent distortion of the thin-walled pipe members

Helical Strip Attachment

The helical flow disruption strips are typically attached to the pipe surface using welded tabs or adhesive bonding. For welded attachment, the following considerations apply:

The welding of small tabs to thin-walled pipe members can cause local distortion and warping
Heat input must be carefully controlled to prevent burn-through or excessive HAZ softening
The weld schedule should be designed to minimize residual stresses, using techniques such as back-step welding or pulse welding
The attachment welds must be designed to withstand long-term vibration fatigue, requiring appropriate fatigue design categories

Fatigue Considerations

The addition of dampers and flow disruption strips creates new stress concentration points on the tower members. The fatigue life of these details must be evaluated according to the relevant standards (e.g., Eurocode 3, Part 2, or API RP 2A). The vibration control devices themselves are also subjected to cyclic loading and must be designed for the expected number of load cycles over the design life.

Study Insights and Engineering Implications

This research represents a significant advance in the wind engineering of ultra-high voltage transmission towers. The combined control strategy of using viscoelastic dampers, TMDs, and helical flow disruption strips addresses both global and local vibration modes simultaneously, which is essential for the reliable performance of 1000kV towers.

From a materials and fabrication standpoint, I emphasize that the long-term reliability of the vibration control system depends on the quality of all welded connections. The damper mounting welds, in particular, are subjected to continuous cyclic loading and are potential fatigue initiation sites. I recommend that fatigue crack growth monitoring be incorporated into the maintenance program for towers equipped with these control devices. The use of high-cycle fatigue resistant steel grades (such as those meeting the requirements of ASTM A709 or equivalent) for the tower members and damper attachments would be beneficial.

Furthermore, the environmental conditions at the tower locations (temperature range, humidity, corrosive atmosphere) must be considered in the selection of damper materials and protective coatings. The viscoelastic damper material properties are temperature-sensitive, and the design must account for the full range of service temperatures to ensure effective vibration control throughout the year.