BRIDGE 52, EAST COAST MAIN TRUNK LINE
In December 2013 HEB was awarded the contract to replace Bridge 52 on the East Coast Main Trunk Line (ECMT). The bridge swap was successfully completed during a 36 hour Block of Line (BOL).
The existing bridge was constructed in the 1920s and spanned 70m across the Waipapa River in Omokoroa. Seven steel girders were supported by 3 large concrete piers and 3 sets of timber piles and piers.
In the 1990’s Smithbridge upgraded the abutments and installed new bored piles.
Novare designed the new steel ballast bridge from weathering steel, consisting of 4 spans, 1 short span at either end and 2 large 30m spans in the middle. The new spans are supported on 6 new 1500mm dia bored piles with 3 new concrete piers.
Prior to the BOL, HEB undertook 10 months of preliminary construction works, which included fabrication of new steel girders (by Eastbridge), installation of temporary staging either side of the existing bridge for access, installing 1500mm dia cased bored piles, with reinforced concrete plugs to a depth of 48m and construction of the new concrete piers.
The main 30m long steel girders were landed onto the new wider concrete piers to reduce the amount of work during the BOL. This was all completed while the rail was operational; up to 12 trains were moving through the site daily.
As the BOL date was set for early January, everything was planned and booked well in advance due to the traditional supply-chain shut-down over the Christmas period.
The rail was closed for 36 hours with 2 crews of 20 - 30 men working 12 hour shifts. The existing bridge was demolished, including taking off the rail, removing the spans, cutting the timber piles and wire sawing 30t sections of the existing concrete piers. The main girders were then craned into their final positions ready for the ballast trays.
The short spans and ballast trays were transported from the laydown yard by HEB Heavy Haulage and lifted into positon. 700 bolts and 10 sets of K braces had to be installed and tightened using the part turn method. Handrails and service ducts were installed. KiwiRail crews then installed ballast, and laid sleepers and track. HEB staff hand-mixed 80 bags of cementitious grout and installed 32 hold down bolts.
Please click here to view a time-lapse video of the complete bridge construction