Princes highway upgrade Berry to Bomaderry
SUMMARY Project: Princes Highway Upgrade – Berry to Bomaderry
Builder: Downer Seymour Whyte Joint Venture (DSWJV)
Architect and Engineer: Arcadis
Client: Transport for NSW
Location: New South Wales South Coast
Description: The installation of weathering steel girders on a challenging site called for an experienced approach to materials and processes.
CONTEXT
The $450m Berry to Bomaderry Princes Highway upgrade is a 10.4 km stretch of road that includes two new bridges.
Strongs Rd, in Jaspers Brush, is a 55 m-long single-span bridge.
Pestells Lane, in Meroo Meadow, is a three-span bridge with a total length of 100 m.
The client, Transport for NSW called for flexible engineering and rapid construction solutions, to reduce disruption to motorists
SOLUTION: WEATHERING STEEL
Steel was chosen for the girders to satisfy the complex geometries and long spans involved, resulting in a lighter structure. Weathering steel (known as REDCOR) was specified to reduce maintenance over the 100-year life of the bridges. Weathering steel requires no painting, which on conventional steel structures is reapplied every 25-30 years. But it does require careful installation to preserve its unique appearance and structural integrity.
6 massive trough-shaped girders made up the design for the 2 bridges. They were constructed from 15 prefabricated sections, each measuring 2 m wide and up to 40 m long and weighing up to 50 tonnes. The 15 sections, made by Civmec, moved under police escort from Newcastle some 300 km to the work site. There, they were all craned into position in just one night, thanks to an innovative temporary support system developed by Riddwood.
RIDDWOOD CONSULTING ENGINEERS
Riddwood was asked to develop a temporary restraint and positioning system, allowing the crane to release the girders before jacking and assembly got underway.
A LOW-COST, LOW IMPACT AND EFFECTIVE IDEA
In consultation with the builder, Riddwood developed a three-part solution for supporting and positioning the 15 steel parts while the 6 girders were assembled.
The first part was a series of heavy duty shoring towers that could take the weight of the steel and allow work to proceed in safety. Key to this was establishing a sound foundation that could be overlaid by subsequent roadworks.
The second part used temporary cradles to prevent the steel sections from moving after they were released from the crane. The site’s proximity to the coast meant that high winds had to be anticipated in the design of the temporary supports.
The final element was a set of button jacks positioned on the towers and the girder beds. The jacks provided the means to locate the steel sections into final alignment
The use of hired proprietary systems over bespoke tooling kept the client’s costs to a minimum, without compromising the safety or effectiveness of the project.
OUTCOME
Key to the success of this design was Riddwood’s experience in both temporary and permanent construction works.
The modular nature of the towers and cradles suited a site that offered limited manoeuvrability.
The girders were released from the crane quickly, reducing the overall lift time and minimising disruption to motorists. Moving each section required less than nine minutes of traffic disruption per girder.
The girders were all placed using stop-go traffic control, reducing the need for a road occupancy licence for the duration of the lift.
The overall speed of the lift saved the client significant money in crane hire fees.
The choice of hired components over custommade structures resulted in limited waste of materials and budget.
The temporary support and cradling system absorbing the mass of the girders enabled work to continue in safety over ensuing months.
The temporary works designs did not over-stress the permanent structural elements.
Once the bridges were complete and the temporary support system removed, there was no visible evidence of their use.
Riddwood Managing Director, Conor Martin said “We optimised our design of the temporary structures by first taking the time to understand the bigger picture.
Our extensive knowledge of proprietary materials and equipment reduced the client’s requirement for capital expenditure and produced a higher value outcome.
It’s an example of a company being big enough to deliver on major projects, but small enough to care.”