Slope no problem

The construction of a steep, long-span bridge in eastern Australia required its structural bearings to be designed for installation at a very high gradient.

The New England Highway in New South Wales, the inland alternative to the Pacific Highway between Sydney and Brisbane, crosses challenging terrain in places – not least at Bolivia Hill, where the highway traverses a particularly adverse landscape. A new bridge is currently being constructed to enable traffic to pass through this area much more safely and quickly, and the local terrain has left its mark on the bridge’s design. The cast in-situ concrete box girder bridge, constructed by the balanced cantilever method with a superstructure depth of up to 8.5 m, has a main span of 150 m and outer spans of 80 m and 86 m respectively. Added to these impressive dimensions and the lack of symmetry is the bridge’s enormous gradient of 8.2% from one end to the other – an exceptionally high slope for a major road bridge of any kind.

In order to support the superstructure at its ends, where its design requires movements to be accommodated, large structural bearings were required – and these had to be designed to be installed at the same gradient as the bridge’s surface (thereby avoiding lifting/lowering of the superstructure as the bridge expands/contracts, which would form a step in the driving surface at each end). Structural bearings of the RESTON®SPHERICAL type were selected for use – a type that can accommodate very high rotations and offers especially high strength and durability. To meet the project’s requirements, these structural bearings were designed to carry a normal load of 11,500 kN and to accommodate either unidirectional or multidirectional movements. The spherical bearings were equipped with anchor plates for easier future repair or replacement, and with an inclined transition plate beneath each bearing to enable it to be installed on a horizontal substructure.

Testing of the bearings has now been carried out, at a gradient of 8.2% from horizontal, at mageba Australia’s in-house nationally-certified testing laboratory in Sydney – verifying that these optimally selected bearings will perform as expected when installed at such a high slope in this impressive structure.

Bridge designer: ARCADIS
Contractor: Georgiou-SRG JV
Bridge owner/Client: Transport for New South Wales (TfNSW)

Representation of how the Bolivia Hill bridge is expected to look when construction has been completed

©NSW Government

Longitudinal drawing of the bridge showing its very steep slope of 8.2 % from one end to the other

Design representation of one structural spherical bearing type, showing the steep slope of 8.2 % at which it will be installed

Lower part of one spherical bearing during assembly, showing the high gradient provided for by its design

Fabrication and assembly of the bridge bearings was carried out in mageba’s Shanghai factory

Testing of a bearing, at the applicable gradient of 8.2% from horizontal, at mageba Australia’s in-house NATA-accredited (ILAC MRA) laboratory in Sydney