Foundation is set, bring in the beams
Building on foundations
In July, HEB Construction began installing the 152 spans that make up the superstructure of the Te Whau Pathway sections currently under construction. Superstructure means the elements of a boardwalk span that are constructed above the foundations. This includes beams, blockings and decking. Span refers to the distance from one set of piles to the next, it is like a section of a bridge.
Each span contains 6 prestressed pre-cast concrete beams (or ‘girders’) made by running steel strands through a mould and pre-stressing them. Pre-stressing means pulling on the strands and stretching them tight like a rubber band before the concrete is poured. After the concrete has set, the strand is released and the stress is transferred into the beam. This gives the beams extra strength and means they can cover a greater distance between piles than they would if they had not been pre-stressed.
Did you know the Auckland Harbour Bridge has nine spans?
The beams are connected by cross members (sturdy braces or reinforcements) called blockings which are bolted through the beams to create the supporting layer for the decking panels to go on. There are eleven blockings per span, so 1672 blockings will be used in the current construction areas. The blockings are fabricated locally in Henderson by local supplier Manson Engineering.
120 African elephants
There are 912 beams to be made for the current construction areas. Each beam weighs 890kg, that is a total of 811,680kg of beams or 120 African elephants! The girders are being fabricated off-site by HEB Construction’s precast division. Girders are cast in sets – four at a time – 228 castings to complete these sections of the project.
As at 31st of July 2024, 78 beams and 143 blockings had been installed. 214 beams had been cast.
Te Kōwhai Nui in place and ready to go
In case you missed it, Te Kōwhai Nui, our travelling gantry, has also now been lifted onto the pathway on the Bridge Ave to Roberts Road connection.
Background to Te Kōwhai Nui
Full-sized travelling gantries are popular in large-scale bridge construction. Te Kōwhai Nui is a mini travelling gantry that has been scaled down to fit, move and turn on the 4-metre wide Te Whau Pathway superstructure with minimal impact on the Whau River. Freyberg Community School students named Te Kōwhai Nui in 2022.
In this video from May 2024, HEB Construction engineer Tim Pervan talks about the mechanics of Te Kōwhai Nui in the video below.
