Abstract
An integral abutment bridge (IAB) is a type of bridge design that eschews the use of expansion joints and in the case of full integral abutment bridge, bearings as well. It has become an increasingly popular design choice for bridges of short to medium length in many countries, including Australia. This is because IABs avoid costly maintenance and serviceability issues arising from persistent and recurring degradation of expansion joints. Additionally, IABs are also generally found to be cheaper and faster to construct than traditional bridge design.However, IABs also experience issues with accentuated soil-structure interactions resulting in lateral earth pressure ratcheting on the bridge abutment and increased settlement bump at the bridge approach. This is largely a consequence of changes in the bridge span produced by ambient thermal variations not being accommodated by the expansion joints but are now transferred to the abutment interacting with the backfill soil. The literature review of this thesis showed that most researchers tried to study these issues through the investigation of the soilstructure interaction behaviour under the assumption of uniform annual (large amplitude) cyclic integral bridge abutment movements caused by smooth and uniform peak-to-trough seasonal ambient temperature changes. Yet ambient temperature changes are not smoothly and uniformly seasonal, not to mention that within a season there are also variations in diurnal ambient temperature causing diurnal (small amplitude) abutment movements. The effects of irregular ambient temperature changes on soil-structure interactions of the integral abutment are further compounded by short term surges in ambient temperature due to bushfire events which frequently occur in New South Wales (NSW).
This thesis studied the effects of irregular soil-structure interactions of integral abutments where very limited literature exists, including the ambient temperature surges from a bushfire event where records of integral abutment movements are not yet available. Therefore, a symmetrical three-dimensional Finite Element Model (FEM) of an integral bridge was developed and subjected to ambient temperature changes from a one-in-fifty-year bushfire event to predict the abutment movements. The effects of soil-structure interactions from irregular translational abutment movements, including those simulated for the bushfire event by the FEM, were investigated using a half-scale physical model developed ensuring the stress-strain similarity with the full-scale prototype.
The results showed that the translational movements in the integral abutment, with uniform diurnal cyclic movements would generate higher slumping and settlement in the backfill, as well as higher lateral pressure at the soil-abutment interface compared to the translational movement without diurnal movements. The bushfire event produced a surge in lateral pressure on the abutment and a jump in settlement. However, after the fire front had passed, the surge or jump representing a sharp rate of increase would stabilize to a similar rate prior to the bushfire event.
| Date of Award | 2023 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Chin Leo (Supervisor), Samanthika Liyanapathirana (Supervisor) & Pan Hu (Supervisor) |