Midland Line Bridge 28 “Sloven Creek”

Key Client: 
KiwiRail
Location: 
Midland Line- between Staircase and Craigieburn.
Project Scope: 

Bridge 28 on the Midland line is a 166m long bridge which has suffered from deterioration of various components through time. Replacement of the rail beams was necessary to reduce the risk of line closure due to failure.

Vitruvius’ role was multi-disciplinary on this project. Vitruvius were appointed in the Project Management role as well as survey and track alignment design.

The Bridge 28 structure has been designed with eight rail beam spans of which three of the spans were designed to flex in a dynamic behaviour.  All new rail beams were delivered on site as two pieces each. The two pieces of each new span gave the Contractor the ability to swap out the old wooden rail beams one side at a time. The benefit of this was that it gave time for rail beams to be replaced between scheduled services on the Midland line, resulting in minimal disruption to core services.

To account for the bridge structure flexing the track alignment had to be designed in two states, static and dynamic.  Vitruvius verified the design states to within construction tolerances post construction using two DX locomotives weighing approximately 200 Tonnes.