West Gate Bridge: mobile bridge inspection platform

Melbourners 2.5km long West Gate Bridge includes two concrete box girder approach viaducts, 871m and 670m long, and an 848m central steel box girder portion over the Yarra River. Prior to the recent strengthening project four travelling gantries were permanently suspended off the steel spans for maintenance and inspections and there was no provision for access to the outside of the concrete spans, although a variety of temporary measures had been adopted from time to time. As part the strengthening project, which included the addition of a fifth lane to each carriageway, the gantries on the steel spans had to be replaced. Instead of replacing them with new suspended gantries, the decision was made to procure a Mobile Bridge Inspection Platform (MBIP) that could be used for the full length of the bridge. The MBIP is the biggest of its kind in Australia and includes a 20m long telescoping platform that can be extended under the bridge as far as the centreline of the bridge soffit. The MBIP stands on the roadway adjacent to the outer barrier. This paper summarises the investigation that lead to the decision to adopt an MBIP rather than permanent suspended platforms.