A transformer fire at a wind farm in New Mexico damaged the foundation of one of its wind turbines. After taking the tower out of service, the client hired Barr to evaluate the fire damage and determine its effects on the foundation’s structural integrity.
Our inspection and analysis of the foundation’s concrete and the steel anchor rods began with a survey of engineering literature for guidance on the permanent effects of fire on structural steel performance. This directed our plan to assess the effects of the fire on the anchor rods.
We worked with a subcontractor to visually inspect the foundation concrete of the wind turbine pedestal and perform materials testing. The subcontractor conducted concrete coring and petrographic analysis. The inspections showed evidence of charring on the pedestal concrete nearest the fire. The petrographic analysis found that while the outer surface of the concrete pedestal suffered thermal cracking, the fire had induced no chemical change. We tested the anchor rods using tension testing and a second method that involved use of a surface-hardness tester to estimate the anchors’ tensile strength. Our research, testing, and analysis indicated that the anchors could be reused with no expectation of reduced performance and that the concrete pedestal suffered no degradation from the fire.
We recommended cosmetic repairs, original grout removal, and clean-up of loose concrete and other debris. After these repairs were completed (and the transformer was replaced), the client placed the turbine back into service without incident.