In last Friday’s story about a tower collapse that occurred two years ago in Lincoln, NE, “New Steel to Rise at Collapsed Tower Site,” we quoted the Lincoln Journal-Star story saying the reason for the structural failure was never determined. Not so.
Actually, two towers went down, the other was KHGI-TV, owned by Gray Television. An engineer with Sinclair-owned KFXL said the failure was due to anchor shaft corrosion.
He also said a tower crew was scheduled to climb the tower that same day only 35 minutes after the failure occurred.
“Unfortunately, this mode (underground and undetected corrosion) of failure happens more often than reported,” said Dave Davies of DKD Engineering. “Most reports reference broadcast towers. But cellular towers typically go under-reported,” he said.
As the incidence of this type of failure increase, Davies said the authors of the TIA-222-H standard address this problem in three separate sections of the new standard governing the design and analysis of towers.
- TIA-222-H: Section 14.4: Guy Anchor Shafts (page 14-1)
Guy anchor shafts with steel in direct contact with soil shall be assessed in accordance with a corrosion management plan based on site-specific corrosion conditions.
- TIA-222-H: Annex J: Maintenance and Conditional Assessment (page J-1)
For guyed masts, prior to climbing, the condition of the guy anchor shafts with steel in direct contact with soil shall be assessed in accordance with the corrosion management plan for the site prior to maintenance and conditional tower assessment.
- TIA-222-H Annex A: Guy Anchor Shafts (page A-5)
The interval and extent of inspection of guy anchor shafts with steel in direct contact with the soil shall be in accordance with a corrosion management plan established by the owner. Depending on corrosiveness of soil and based on site-specific corrosion conditions.
- The mentioned Corrosion Management Plan consists of Inspection, Remediation, and Maintenance. It is the tower owner’s responsibility to enact and complete the CMP prior to allowing personnel to climb the tower.
- The TIA-222-H Standard became effective January 1, 2018 and is part of the IBC 2018 code. However, it must be accepted on a state by state basis which is an on-going process, according to Davies.
“The contained Corrosion Management Plan will certainly be beneficial to the tower industry as it increases the tower owner’s due diligence requirements to maintain a safe work environment for tower crews,” Davies said.
August 6, 2019