For decades, the transmission line industry has grappled with the persistent challenge of weld fatigue failures in unloaded davit arms—those slender, conductor-free arms awaiting future use on transmission structures. Traditionally, solutions have focused on altering the natural frequency of these arms, employing methods such as suspended weights, empty insulator strings, or arm ties. While these approaches have provided incremental improvements, they often come with added complexity, cost, and installation time.

Verdantas, leveraging its multidisciplinary expertise in Flow Labs, CFD modeling, and Energy Transition, has pioneered a novel, cost-effective solution: utilizing the perch preventer. Rather than targeting the arm’s resonant frequency, this approach disrupts the fluid dynamics responsible for vortex-induced vibrations (VIVs)—the root cause of weld fatigue.

The perch preventer, a series of conical guards installed along the davit arm, fundamentally alters the cross-sectional geometry. This simple modification not only deters birds from perching but also transforms the way wind interacts with the arm. Computational Fluid Dynamics (CFD) analysis, performed by Verdantas’ Flow Labs, demonstrates a dramatic reduction in damaging vortex shedding. The ratio of forcing frequency to natural frequency (“r”) drops from 1.2 to 0.02, effectively eliminating resonance at critical wind speeds and removing the structure from the lock-in region where fatigue failures occur.

This breakthrough is more than an engineering solution—it’s a testament to Verdantas’ collaborative culture. By integrating insights from our Energy Transition group and Flow Labs, we’ve developed a solution that is both practical and scalable. The perch preventer can be quickly installed, requires minimal maintenance, and opens the door for further innovation in the design of slender structures, especially for high-voltage applications.

Our approach is validated by rigorous CFD modeling and modal analysis, suggesting that changing the geometry, not just the mass or stiffness, can mitigate VIVs. The method can be further validated through wind-tunnel or real-world testing. The implications extend well beyond transmission line structures; any industry facing vibration challenges in slender structures could benefit from this methodology.

At Verdantas, we believe that true innovation happens at the intersection of disciplines. By fostering collaboration between our modeling experts and energy strategists, we deliver solutions that are not only technically sound but also aligned with the evolving needs of our clients and the energy sector.

As we continue to push the boundaries of what’s possible, Verdantas remains committed to advancing reliability, safety, and sustainability in transmission infrastructure. The perch preventer is just one example of how our integrated practices drive meaningful change, reducing risk, improving performance, and setting new standards for the industry.

This article is based on research by Gokul Narayanan and Abdelrahman “Sabrah” Ahmed, Duncan Phyfe and Jaqueline Anderson of Verdantas, LLC.