Bridges

The replacement of the aging railway bridges in the existing railway network will always result in disruption to rail operation and inconvenience to the commuting public. The construction time has also been a major constraint to the design, and so are the construction procedure and timing. This essentially means that the design solution has to lead to a fully prefabricated construction without any in situ concerting works. Furthermore, in many cases geometric constraints add another challenge to the designer and constructor because the requirements for headroom clearance under the bridge (in the case of a road overpass) and horizontal clearances adjacent to the track have increased since the time the existing bridge was constructed. The required structural depth of the replacement bridge may also need to be greater than that of the existing bridge since the design live load has considerably increased. Raising the existing rail levels to accommodate additional structural depth and headroom clearance will result in track work on both approach ends and thereby increasing the work during a weekend shutdown. In many cases along the metropolitan lines, the bridges are located very close to the station platforms and consequently it is not possible to raise the track levels.This paper presents the design innovations used in the design of Victoria Street and Langridge Street replacement bridges on the South Morang line in Melbourne, to enable both bridges to be replaced within weekend rail shutdowns. The presented solution is relevant to the case of these bridges but it could serve as an example to other bridge replacement projects.