Bridges

Currently, seismic design of bridges in Australia is carried out in accordance with Section 14 of AS 5100.2:2004. The design process is similar to that in AS 1170.4:1993 but focused on bridges rather than buildings. Some of the design parameters used in AS 5100.2 directly reference AS 1170.4:1993. However, due to the update of AS 1170.4 published in 2007, the references in AS 5100.2:2004 are now out-of-date. This paper discusses the work carried out under Austroads Project TS 1599 Guidelines for Seismic Design of Australian Bridges as detailed in the project report. The project reviewed current design codes and highlighted updates required to Section 14 of AS 5100.2:2004 to accord with AS 1170.4:2007. AS 5100.2:2004 uses the principles of the conventional Force-Based Design Method (FBDM) with generalised acceleration spectra to determine the relevant seismic actions. Project TS 1599 provides an alternative approach, using the principles of the Displacement-Based Design Method (DBDM). The DBDM assesses the effects of seismic events by considering displacements and strains of the deformed structural elements in contrast with the FBDM approach which only considers forces and subsequent design action effects. The DBDM enables designers to predict a structure’s behaviour and/or damage from the design seismic event, and provides a tool to check whether a structure can be exempted from specific seismic design provisions. The project also reviews the current seismic detailing provisions in AS 5100.5. The outcomes of the project will be submitted to Standards Australia for incorporation into the revision of AS 5100 currently underway.