By the National Precast Concrete Association Australia

As road and infrastructure projects multiply across the nation, there’s a high demand for products with higher-than-usual lead times for precast concrete pipes and other stormwater products. But when inferior, untested products are unknowingly used, there can be a drastic negative impact on the lifespan and structural integrity of the project.

When it comes to construction projects, the devil is in the detail – that’s why the usage of properly tested and quality products is essential.

According to National Precast CEO, Sarah Bachmann, inferior products like raw cast liners are on occasion being substituted for their superior alternative, spun reinforced precast concrete liners. “It is concerning that some authorities are installing the inferior alternative, unaware of their actual performance,” Ms Bachmann said.

Unlike spun liners, raw cast liners do not comply with AS/NZS 4058 Precast concrete pipes (pressure and non-pressure), a typical requirement of roads’ authority specifications. Raw (or dry) cast liners are not spun, use very little reinforcement (or fibre reinforcement) and are typically untested and not manufactured to ISO 9001 accreditation.

A WA-grown solution

Located in Australind, Western Australia, National Precast Master Precast member MJB Industries has made the manufacture and supply of Class 2 spun liners a priority in its new pipe plant.

Its original bidirectional pipe plant is currently operating at full capacity, with a production schedule booked months in advance. MJB Director, Kim Hovey, said the new plant’s first priority will be to produce spun liners, stockpiling them for current and future orders.

“Our second pipe plant will be operational in the third quarter of this year and will greatly increase production output and reduce lead times,” Ms Hovey said.

“Our spun liners are made to meet Main Roads Western Australia Specification 405, which require precast liner segments to be manufactured to AS/NZS 4058.” Ms Bachmann said that there are a limited number of manufacturers able to produce these spun liner products in the West.

“Other manufacturers of raw cast liners – that do not conform to AS/NZS 4058 – are not an equivalent alternative and do not meet Main Roads Western Australia specifications,” Ms Bachmann said.

Education is key

Ms Bachmann said this is an industry-wide issue that requires better understanding by everyone involved in roads and infrastructure projects. “Compliance to Australian Standards and specifications is imperative for the longevity of our roads networks and I’m pleased to say that our Master Precasters, like MJB, ensure they do just that,” Ms Bachmann said.

Why continuous Teeroffs?

Continuous Teeroff beams are typically used in the construction of long-span bridges and other large infrastructure projects and are more efficient for elevated motorways, which are necessary due to the increased urbanisation of cities and the frequent requirement to construct bridges and motorways over existing infrastructure. Their specification has become increasingly common in Western Australia, primarily in response to project specific constraints such as limitations on pier widths and structural depths, and heavily loaded edge beams on Single Point Urban Interchange (SPUI) bridges. The beams have been used in Perth’s $1 billion Gateway WA project that upgraded the road network around Perth Airport, the Reid Highway Duplication over the Mitchell Freeway, and the northern section of NorthLink WA. Similar in shape to standard Teeroffs – with a horizontal top flange and a vertical web – they are designed to be much longer, often spanning hundreds of meters. They are typically constructed as simply supported, with a link slab providing a continuous concrete running surface without any intermediate deck joints. Their main advantage is their ability to support very heavy loads over long distances without the need for intermediate supports. This is achieved by joining multiple beams together with a series of welded or bolted connections, creating a
continuous beam that can span the entire length of a bridge or other structure.

Case study: efficient road construction using continuous teeroffs

Key facts

  • Project: Bunbury Outer Ring Road (BORR)
  • Location: Western Australia
  • Client: Main Roads Western Australia
  • Construction: South West Gateway Alliance consortium (Acciona, NRW Contracting, MACA Civil, AECOM and Aurecon)
  • Master Precaster: Australian Precast Solutions

The Bunbury Outer Ring Road (BORR) project is south-west Western Australia’s largest ever infrastructure project and was first proposed in 2009, with construction beginning in 2016.

The new 27km, four lane ring road – that connects the Forrest Highway with Bussell Highway – consists of dual carriageways, roundabouts, and overpasses. The project is being constructed by the South West Gateway Alliance consortium, comprising Acciona, NRW Contracting, MACA Civil, AECOM and Aurecon.

It forms part of the post-COVID-19 recovery infrastructure programme, with 80 per cent of its $852 million cost being funded by the Federal Government, and the remainder coming from the State Government. The BORR is set to improve access to Bunbury and other regional destinations in Western Australia’s south-west.

Reduced onsite works and costs, and increased safety, are evident in this Western Australian motorway, due to the use of 139 precast concrete Teeroff beams that have been manufactured with strict quality requirements.

As a National Precast Master Precaster – and like other Master Precasters – Australian Precast Solutions has been independently audited by National Precast Concrete Association, to not only ensure its quality systems are being implemented on a daily basis, but safety and environmental systems as well.

Weighing a huge 191t and measuring 41m long, the Teeroffs are 2.2m deep by 4.5m wide, and were manufactured for the project at the precaster’s newly built and commissioned factory in Bunbury.

Of the project’s $852 million cost, around $450 million is being spent with local south-west businesses and $30 million on First Nations businesses, with First Nation employment a priority.

The project is also an example of sustainable infrastructure development, designed with environmental considerations in mind, featuring wildlife crossings which allow animals to safely cross the road without endangering themselves or motorists.

When complete, the Bunbury Outer Ring Road will be a vital artery that connects the city’s northern and eastern suburbs with the South West Highway, easing traffic congestion and reducing travel times.

As well as improving access to Bunbury and other regional destinations, it will also alleviate the convoluted previous freight network that impeded freight and transport efficiency.

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