Assessment of a retrofit solution for the Avondale Road Bridge, Christchurch, against lateral spreading

Major earthquakes provide an invaluable source of case studies. One of their applications is to improve the design of structures to make them safer. Such is the case of Avondale Road Bridge in Christchurch, New Zealand, which was affected by the 2010-2011 Canterbury earthquake sequence. A typical 1960’s bridge, it was struck by four main earthquake events within a period of ten months. These events induced lateral spreading of various amounts at the river banks, ultimately damaging the piled abutments beyond repair and resulting in excessive damage at its approaches. A new design was subsequently proposed to retrofit the bridge, by replacing the damaged abutments and foundation, while preserving the rest of the structure. In order to study the retrofitted bridge’s behaviour under similar earthquake activity, key bridge parts were modelled at small scale for centrifuge testing. The model was designed, manufactured, assembled and tested at the University of Dundee (UoD) centrifuge facility. It behaved very satisfactorily, indicating that the retrofitted bridge foundation would not be damaged in a similar destructive sequence in the future. The findings were compared to another centrifuge test of the original bridge design under the same earthquake shaking, which replicated the original damage mechanisms accurately.