Q & A With American Tower: Revision I, the Latest Update to TIA-222, a Vital Standard for the Telecommunications Industry

What is TIA-222?

The Telecommunications Industry Association (TIA) is an international standards-developing organization, accredited by the American National Standards Institute (ANSI). The TIA supports various initiatives through nine engineering committees and is the administrator for a number of U.S. Technical Advisory Groups, including TR-14. The TR-14 committee leads technical changes and develops the TIA Structural Standard for Antenna Supporting Structures, Antennas, and Small Wind Turbine Support Structures, also known as TIA-222. This tower standard debuted in 1959, with the latest update, Revision I, taking effect on January 1, 2024.

What types of businesses and organizations serve as members of the engineering committees supported by TIA, specifically the committee that worked to develop Revision I?

Representatives from tower owners, mount and tower manufacturers, and national mobile network operators, along with other consultants, were on the committee that worked to develop the updated standard. 

Why is Revision I important for the telecommunications industry?

TIA-222-I reflects information from the previous revision—Revision H—and offers further updates based on the latest industry knowledge and supporting references, such as the American Society of Civil Engineers (ASCE) 7-22, to uphold the safety and integrity of tower structures. In recent years, as wireless network equipment has evolved and become larger and heavier, instances of mount failures leading to tower damage have been increasing across the industry. This latest revision builds upon the importance of mount analysis to ensure the reliability of tower structures and the equipment connected to them. The criteria set forth in this revision also influence the calculation of equipment loads for tower structures, which can impact capital and operational costs, profitability, and service quality for end customers.

Can you describe the level of change Revision I is bringing, when compared to the previous revision of the standard, Revision H?

While Revision I takes into account the industry technology and information advancements of today, it isn’t bringing the same level of change complexity as Revision H brought to the standard in 2018. This revision is designed to keep pace and align with changes presented in the ASCE 7-22, Minimum Design Loads and Associated Criteria for Buildings and Other Structures, and the International Code Council (ICC) 2024 International Building Code (IBC). 

What are some of the key changes established in Revision I?

Several sections were updated in this revision. For loads, there are updated exposure and topography equations, updates to seismic load calculation, and tornado and fatigue load considerations that have been added. When considering existing structures there is clarification on changed conditions; a requirement for full, comprehensive structural analysis; relaxed tolerances on guy wire tensions and plumbness for monopoles; and drones/UAS (unmanned aerial systems) have been added as an acceptable method to collect data. Regarding mounts, mount-to-leg interaction calculations, a mount post-modification inspection requirement, and rooftop mount reference and design criteria have all been added.

Can you expand on the updates related to mounts?

Absolutely. The changes outlined in Revision I impact how mounts are considered, what a mount analysis should include, and when mount analyses are required. Conducting a mount analysis, whenever there is a changed condition for the appurtenance mounting system, previously became an official requirement under Revision H. In Revision I, there are additional requirements, including:

• Evaluation of the Mount-to-Tower Interaction (MTI) is now a required analysis; this is an evaluation of the local stresses on the tower at the specific locations where the mount interfaces with the tower.
• Mounts located on alternative infrastructure, such as buildings, water tanks, and electrical transmission towers, had been differentiated from mounts located on traditional macro cell towers; there are now separate loading considerations specific to mounts located on these alternative infrastructures defined. 
• Mounts must now be inspected whenever a new mount is installed or an existing mount is structurally modified; this is commonly referred to as mount Post-Modification Inspection (PMI).
• Periodic maintenance/condition assessments for mounts are exempt from the new standard requirements, as the expectation is that when the new mount PMI requirement is followed, additional inspections should not be necessary to ensure the safety and condition of the mount.

You mentioned one of the changes in Revision H, the previous revision of TIA-222, was the requirement of conducting a mount analysis when there was a changed condition for the appurtenance mounting system. What does a mount analysis entail?

A mount analysis is a structural analysis of the appurtenance mounting system to confirm it is structurally sufficient to support the proposed equipment configuration. This important analysis can identify any fit-up issues with the structure and serviceability concerns (i.e., does the mount design, or the way the equipment is installed, make it likely the mount may deflect in such a way that Radio Frequency (RF) performance will be negatively impacted?); determine the site-specific installation configuration of the mount and the antennas it supports; and confirm the impact of the mount on the structural capacity of the asset.

Is there new guidance on defining structure classification and ice loads, and can you elaborate on updates to wind loads?

In general, structure classification, known as Risk Category, remains identical from Revision H to Revision I. The same methods and recommendations which identify a structure as Risk Category I, II, III, or IV still apply.

Regarding ice loads, the maps detailing ice thicknesses have reduced in some instances, based on additional available environmental data. Generally, this results in lower load demand on telecommunication structures, specifically guyed towers. 

For wind loads, there are a few changes in Revision I that will impact telecommunication structure design and performance. Specifically, the equations modeling topographic features (i.e., large hills, ridges) have been changed and, in some cases, require more detail. However, these changes only apply to new structures.

Wind loads from tornados are included in Revision I, but are only applicable for Risk Category III and IV structures. Generally, this will only have an impact to areas in the Central U.S. It’s important to note, tornado-related loads are addressed for survival of structures near tornado impact, not to withstand direct tornado-level wind loads.

Also, direction is provided regarding the use of wind tunnel and computational fluid dynamic-derived loads. This is relevant as many wireless equipment providers are now doing this research/testing and making this data available.

Fatigue loading considerations are now included, which can impact monopoles. The fatigue provision focuses on connections that are prone to fatigue-related failure, such as base plate and anchor bolts. Fatigue checks are optional, but if incorporated in the analysis could result in less computational overall load demand on the structure.

How are seismic designs affected by Revision I?

For seismic design, the design loads were updated to be consistent with recommendations from ASCE 7-22. While the design equations applied do differ in some aspects from what was used in Revision H, the resulting impact on telecommunication structures is largely the same. Basically, this means wind and ice loads will still almost always result in higher loading on the structure vs. earthquake loads.

How can someone access a copy of TIA-222-I?

You can purchase a copy of TIA-222-I on the TIA website: https://tiaonline.org.