- Publication no: ABC2017-083-17
- Published: 21 April 2017
The North Island Main Trunk Line is the main railway line in the North Island between Auckland and Wellington, in New Zealand. This line, owned and operated by Kiwirail, provides key freight and passenger services along the length of the North Island. On this route 7 timber bridges located close to Taumaranui, located in the central north island, and one close to Taupiri, south of Auckland, were identified for replacement due to their age and condition.
The project was a Design and Construct project where AECOM partnered with Downer Construction to design and construct the upgrade and replacement of existing timber high risk structures to increase the reliability of the network and to support freight growth by allowing an increase in the axle load and speed.
This paper discusses the design and construction challenges faced in this project in order to meet the desired objectives set out by KiwiRail which were to provide economical ‘fix and forget’ type solutions for each of the bridge replacements, providing reliability to the network in a seismically susceptible area, and developing designs which can be constructed in short 24hr or 48hours Block of Line.
The key technical challenges which will be discussed in the paper are: Weathering steel and superstructure design, seismic design philosophy of the bridges, economical design to deal with liquefiable soil and soft soils; practical challenges during construction of the bridges in a live rail corridor and working around existing fragile structures; including staging and construction methods, and working during a 24hr and 48hr hour block-of- line.