Your Council

Milson Line overbridge seismic assessment

Wednesday January 15 2014

Council has completed initial investigatory work on the earthquake risks to the Milson Line overbridge.

The overbridge was constructed in 1928 as part of the early stage work on the Milson Railway deviation that was completed in 1959. The overbridge was widened in 1964 to add footpaths and service ducts to both sides of the bridge.

Consultant engineers from Opus International Consultants inspected the bridge and completed an assessment in August 2011. That report identified that the bridge has the capacity to withstand earthquake forces up to a 100 year return period event in the longitudinal (end-on) direction only. An earthquake force of that magnitude arriving in the transverse (side-on) direction could damage the structure and make it unserviceable.

Opus recommended an option that would address the risks for an earthquake force in the transverse direction. Improvements were estimated at $725,000.

Council has considered that report and the likelihood of receiving funding support. A recommendation has been made to not proceed with the strengthening work at this stage as the repair work would only marginally alter the structure' s ability to withstand an earthquake and strengthening work would not substantially change the risks to the community.

Further consideration will be given to replacing the structure as part of the review of Council's Asset Management Plan.