February 18, 2016 — The tower engineer’s workload has experienced major changes in the last 20 years. With the slowdown of new tower sales, the engineer’s work has changed from new tower design to tower modification design. In many cases, tower mods are more challenging than new tower designs because the engineer is not intimately familiar with the tower he is working on nor does he have enough information to do an analysis. The owner’s expectations to save money by modifying a tower as opposed to replacing it is a reasonable assumption, but in most cases they are in for a shock.
Many times the cost of a tower modification exceeds the cost of replacing an existing tower, but often, owners have no choice in the matter. The tower owner has to consider the loss of revenue and possibly losing tenants if they decide to build a new tower. The loss of service for the tenant and the cost of replacing antennas and rearranging lines to get back in service is very costly. And, sometimes, the local municipality refuses to allow a new tower to be built, so modifying the existing tower is their only solution.
Modification for additional loading was never given a thought in these original tower designs, so now engineers are scrambling to produce modification designs on a tight schedule and budget. Engineers are left with no alternative other than scab welding half round tubing to existing round members, welding or u-bolting on new gusset plates for mid-point bracing, u-bolting angles to the outside of the legs and an assortment of other remedies, none of which is optimal.
The modification work that is currently ongoing is realistically nothing more than a band aid on a serious wound. We don’t know for sure what the needs of the next generation of technology will bring in respect to loading, but more than likely it will increase loading and therefore require another modification. Additionally, a new generation of standards committee members wanting recognition in pride of authorship may initiate changes in the standards that result in even more alterations and modifications. Since the EIA specifications governing tower designs were adopted in 1987, the minimum requirements for the design of steel towers has been a moving target from TIA-222 Revision C to TIA 222 Revision G.
This situation is a catastrophe that needs to be fixed. Maybe federal regulations should be imposed that force municipalities to allow owners the right to replace their towers with heavier towers, towers that are designed so they can be modified for future loading. Maybe consideration should be given to reintroduce the square angle iron towers to allow easy modification. Maybe the wrap-around tower being installed over the existing overloaded tower is an option, one that has been done several times but is seldom seen.
Whatever plans the powers-that-be adopt, it needs to be done quickly. This is the American telecommunication infrastructure we are discussing here. The fact that professional organizations have allowed our infrastructure to deteriorate to this level is an international embarrassment. When it reaches a point where a website is created for the sole purpose of reporting unsafe towers, it’s time to take positive action to correct the problem.
Richard Bell is president of Bell Tower Corporation