Temporary Works Okahu Viaduct
Temporary Works State Highway 1 Puhoi to Warkworth, NZ.
TGE used advanced modelling to develop temporary crane platforms.
The Contractor elected to lift the bridge girders from a temporary causeway across the marine sediments rather than launch the bridge from the abutments. This required a series of complex lifts, sometimes using two cranes in tandem picking large girder beams, moving, slewing and luffing them into place at reaches of over 30m.
The lifts required the largest crawler cranes in New Zealand, operating on a platform of hardfill overlying seven metres of very soft marine sediments.
TGE were asked to evaluate the feasibility of lifting the girders without installing piled-crane platforms through the causeway into the underlying bedrock.
A load test was carried out using stacks of crane counterweights. The settlement of the stacks was used to calibrate a 3D finite element model which calculated deflections and safety factors for each lift. The methodology was independently reviewed resulting in a permit-to-lift provided by TGE for each of the 14 lifts required to build the viaduct.
