Title: Mitigating Bond Deterioration under Cyclic Loading and Water Exposure
Author(s): Tomohisa Saito, Nobuhiro Chijiwa, Hiroo Shinozaki, and Mitsuyasu Iwanami
Publication: Structural Journal
Appears on pages(s): 17-30
Keywords: anchorage performance; bond deterioration; cavitation; epoxy resin; erosion; fatigue; water; wedge effect
Several cases of premature damage of wind turbine tower foundations constructed using the anchor-ring method have been reported to cause towers’ uplift. Sludge buildup (in the form of crushed concrete) was evident along the periphery of the damaged base towers and was found to originate mainly from the concrete-steel interface around the steel anchor foundation that is embedded in concrete, due to the cyclic movement of the anchor steel and the
induced water pressure at the interface. This study experimentally investigated possible repair and reinforcing methods to mitigate this problem. Cyclic load tests were carried out on three steel anchor mockup specimens. In the first two specimens, the anchor steel was retrofitted with a nonshrink mortar and epoxy resin, respectively, whereas in the other specimen, the anchor steel was further restrained against uplift by additional anchorage bars. The results indicate that the non-shrink mortar was not effective in preventing water ingress into the interface and could only delay the extent of concrete damage and the progress of bond deterioration during cyclic loading. Epoxy resin was found to perform much better in this regard. In addition, the epoxy layer could also help to dissipate the induced bearing stresses under cyclic loading, thereby making it the best candidate for repair and reinforcing materials in such applications. The use of additional anchorage bars was also found to be effective, although it still requires additional measure to prevent moisture ingress.