Effects of bushfire on soil-structure interactions of the integral abutment

Many parts of the world including Australia are increasingly prone to bushfires because of hot and dry climate made worse by climate change. Integral bridges in bushfire-prone areas are at risk of bushfire outbreaks which generate large and rapid ambient temperature increases. As is well known, integral bridges are designed without any joints on the bridge deck to avoid recurring maintenance problems caused by bridge joints, but the consequence is significant, thermal movements of the bridge deck will be transferred to the end abutments, which interact with the adjacent backfill. In the event of a bushfire, the thermal movements of the end abutments that are normally in response to cyclical diurnal and seasonal ambient temperature changes will be significantly accentuated. The soil-structure interactions of the integral abutment subjected to the effects of bushfires are not well understood and have received little research attention despite their potential to cause negative impact. Therefore, this study has conducted physical modeling to simulate the soil-structure interactions under a critical bushfire scenario to investigate the stress ratcheting on the abutment wall at the abutment-backfill interface. The physical model was designed to maintain the same strain and stress levels as a 1.92 m high prototype integral abutment. The study provided interesting insights into the immediate and residual effects on the lateral pressure acting on the integral abutment during and after the bushfire event.