Article

Mount-to-Tower Dynamics: Meeting Challenges with New Strategies & Technology

With the growing demands of modern networks, telecommunication structures are experiencing significantly higher stress due to increased loading requirements. For monopoles, in particular, antenna platforms secured with ring mounts to the pole are crucial for supporting essential communications equipment - and as these loads intensify, the risk of heightened localized stress and potential damage also increases, presenting new challenges that must be carefully managed to maintain the integrity and reliability of these structures.

A Stressful Situation

In 2022, the telecommunications industry began encountering reports of monopole damage and failures due to the increased stress from heavier equipment loading at single point connections. It became evident that many monopoles, especially those with thinner walls, were not equipped to handle these heightened demands. Additionally, factors such as improper installation practices, like over-tightening on mounts, emerged as a significant contributor to structural damage and potential failures. In cases involving our products, there were no reported failures of the actual mounts or collars themselves; rather, the monopoles were unable to support the increased loads. This underscored a broader, industry-wide challenge largely driven by a variety of nuanced factors, including incorrect installation techniques and mounting practices.

In a few instances, we found that the mounting of panel antennas, exceedingly higher than the centerline, was another source of increased stress. The centerline positioning of platforms, particularly when installed at higher elevations, created even greater localized stress on monopoles.

These combined elements revealed an industry-wide issue: a convergence of higher equipment loads, installation errors, and inherent structural limitations that significantly increased the risk of monopole stress and damage. In response, we broadened our efforts to provide educational initiatives aimed at promoting improved installation practices and addressing these systemic challenges.

Causes of Structural Failure

After analyzing industry reports, we identified a range of factors contributing to the main failure modes commonly observed:

• Installation Procedures: Improper installation techniques were a significant cause of structural issues. This includes:
  • Over-tightening: These included over tightening of all-threads, especially on monopoles with thin walls or high diameter-to-thickness (D/t) ratios, leading to excessive stress.
  • Under-Tightening or Unequal Tightening: This was another concern, which could occur when one side of the mount is tightened, causing the other side to loosen without proper checks.
  • Improper Leveling: If the collar is not installed in a level fashion, this leads to increased stress.
  • Improper Positioning: This refers to mounting on non-reinforced sections, such as the top of a pole, which were also significant contributing factors to structural failure.
• Environmental Factors: Wind and ice events were also found to be contributors as well. Typically, ice buildup or dead weight controls added significant weight, inducing out-of-plane bending at the shaft wall, which further stressed the monopole structure and heightened the risk of damage.

A New Place to Look

Historically, the focus of mount design and analysis has primarily centered on the mount itself and the collar, as this was in line with existing industry standards. At the time, there were no established requirements for assessing the interaction between the mount and the structure it was attached to, so analysis typically was terminated at the ring mount, reflecting a gap in broader industry practices. The reason for this was the vast number of possible configurations for structures, making it nearly impossible to perform accurate calculations with so many unknown variables. For example, monopoles can vary in steel grades, tapers, sides, diameters, thicknesses, and heights, all of which can significantly impact the overall capacity of that localized attachment zone. From a manufacturer's perspective, we do not always have full knowledge of the specific characteristics or conditions of the pole on which our mounts will be installed.

Due to the lack of industry standards, the critical interaction between the mount and the monopole structure remained mostly unexamined. In response, we increased our focus on educational initiatives and embarked on developing new models and technologies to address these gaps. This area has become a critical point of focus for our engineering teams, driving them to create more innovative solutions that ensure both the mounts and their interactions with structures reduce the risk of damage and meet the highest safety and performance standards.

Additionally, we have been updating our drawings to include new guidelines and recommendations, detailing the initial and final tightening order to provide clearer guidance for installers. These updates emphasize the critical importance of equal tightening, maintaining proper distance, and other best practices to ensure secure and reliable installations.

Key Installation Observations

Proper installation is critical for the longevity and reliability of monopole mounts, as improper techniques can lead to significant issues, such as stress-induced wall deformation and connection failures. While we cannot provide recommendations for every detail of the installation process, it is generally important to maintain balanced tensioning, avoid over or under-tightening, and follow a systematic tightening sequence to achieve even load distribution.

While we can provide observations and best practices, we cannot specify exact values, such as torque values, because variables outside of our control - such as the type, condition, and specifications of the pole -can significantly impact these requirements. Instead, utilizing snug-tight methods or calibrated pre-tensioning is recommended to effectively secure joints without compromising the structural integrity of the monopole. Adhering to these general guidelines helps mitigate the risks associated with uneven force distribution, particularly in mounts subjected to environmental stresses like wind or ice accumulation.

Example of Improper Installation: Installed Too Tight & Uneven

A clear example of improper installation can be seen in the image below, which shows a Fortress® Tri-Platform Mount installed on a monopole with the ring mount tightened excessively and unevenly on one side. This improper technique caused the collar to be pulled inward, ignoring our spacing recommendations of 120 degrees between points. When we provide installation recommendations, they are based on maintaining 120 degrees of spacing for three-sided mounts and 90 degrees for four-sided mounts, ensuring equal distribution. Failure to adhere to these general guidelines can compromise the engineering integrity, potentially leading to structural damage.

Example of Improper Installation: Installed Unleveled

Another example of improper installation is when the ring mount is installed in an unlevel fashion. This misalignment results in the components not being on the same plane, which introduces prying forces on the threaded rods. Such forces can compromise the stability of the mount and affect the interaction dynamics between the mount and the monopole structure. This uneven load distribution can lead to increased stress points, potentially causing damage and diminishing the overall integrity of the installation.

Real-World Testing Results

Last year InnovX™ 2023, we extensively tested our RM3 and RM4 mounts, and at InnovX™ 2024 this year, we showcased the physical testing of our new ring FLX Series™ Ring Mount with VersaFlex™ Technology, set for release in 2025. These tests were crucial for the validation of thousands of hours of Finite Element Analysis (FEA) work and ensuring our theoretical models aligned with real-world outcomes. We found that the results were within negligible variance, effectively validating our assumptions - an outcome that was absolutely remarkable.

To emphasize the significance of this, physical testing results were within a 32nd of an inch when compared to our models and theoretical assumptions - an absolutely extraordinary achievement for our team and complete validation of our approach and assumptions.

These comprehensive testing efforts, which combine advanced simulations with physical validation, have greatly enhanced our modeling techniques. This integrated approach not only reinforces the quality of our products but also guides future engineering solutions, ensuring that we continue to meet the highest safety and performance standards in the field.

For more details on this testing, please view our webinar titled “Mitigating Monopole Stress: Next-Generation Mount-to-Tower Technology,” available in our webinar library. For more details on this testing, please view our webinar titled “Mitigating Monopole Stress: Next-Generation Mount-to-Tower Technology,” available in our webinar library.

Our Solution: Dynamically Conforming Ring Mount Technology

As a result of thousands of hours of analysis, testing, and refinement, our new FLX Series™ Ring Mount, featuring the patent-pending VersaFlex™ Clamp Ring technology, is now in production. Available in both SD and HD versions, this mount is designed to replace our standard-duty LWRM and UQB4 ring mounts. The innovative design features pivot points between the rods for a better snug fit, minimizing shifted loading. This advanced technology dynamically conforms to the pole, pivoting around it with a round-on-round configuration, significantly mitigating pole damage.

By adapting to the unique characteristics of the pole, the FLX Series™ ensures a secure and balanced installation, enhancing structural integrity and reducing the risk of localized stress. For further details on how this design mitigates damage, see our latest webinar linked above. The mount is constructed as a single weldment, contributing to its higher D/t value.

Proven Unprecedented Performance

During the recent NATE show, we conducted physical testing on the SD version and found it could withstand up to 9,000 pounds of force—nearly double the capacity of the LWRM. Remarkably, there were no local effects observed; beyond a certain point, the entire pole moved as a unit. This result represents unprecedented performance. After removal, the only signs were slight surface scratches, with no local failures—an outstanding achievement that showcases the reliability and resilience of this new design.

Our extensive Finite Element Analysis (FEA) work, backed by thousands of hours of dedicated effort, has been unequivocally validated through rigorous real-world testing, achieving alignment within a 32nd of an inch. Our analysis demonstrated that the load capacity for specific regions correlates with the D/t ratio (diameter of the shaft to wall thickness), showing that higher D/t ratios generally result in lower pole capacity. Updated engineering documentation now reflects this understanding, presenting capacity values based on D/t ratios.

The culmination of this research and testing is our newly developed FLX Series™ Ring Mount, which represents a transformative leap in our mounting technology. This optimized design, based on comprehensive research findings, not only sets a new standard for performance and reliability but also serves as a foundation that informs and guides future designs.

Looking Ahead

The development and validation of our new mounting technologies underscore our commitment to enhancing the safety, reliability, and performance of telecommunication structures. Through thousands of hours of dedicated analysis, Finite Element Analysis (FEA) modeling, and comprehensive real-world testing showcased at our InnovX™ events, we have made substantial progress in understanding and mitigating the unique challenges monopoles face under modern loading conditions.

Our new FLX Series™ Ring Mount, featuring the patent-pending VersaFlex™ Clamp Ring technology, embodies the culmination of these efforts. This breakthrough design adapts to the specific characteristics of each pole, mitigating damage and ensuring secure, balanced installations that exceed current industry standards. The integration of these advancements not only reinforces our products’ durability but also sets the stage for future innovation and design improvements.

Addressing the challenges posed by modern network demands is an industry-wide endeavor that requires collective collaboration. The valued contributions from organizations like the Tower Industry Foundation (TIF) play a pivotal role in pushing the boundaries of what’s possible in mount-to-tower dynamics. We invite you to explore our webinar titled “Mitigating Monopole Stress: Next-Generation Mount-to-Tower Technology,” for deeper insights into our findings and advancements.

Together, as an industry, we are committed to advancing toward safer and more resilient telecommunication infrastructure, capable of supporting the networks of today and tomorrow.

Joseph Trimble

Joseph Trimble graduated from Purdue University-Northwest with a Master of Science in Mechanical Engineering in 2016. While a graduate student, he worked as a researcher utilizing numerical methods such as finite element analysis for structural and fluid dynamic analyses.