Construcciones Yamaro: Behind tilt-panel construction
As tilt-panel construction has become more common on Australian sites, Hobson Engineering has focused on the fastening systems that sit behind it.
Hobson Engineering’s range of fastening systems has grown over recent years, extending into a wider set of applications. That expansion has brought the company into more safety-critical areas of building, including precast and tilt-panel construction.
The development has followed demand, with tilt-panel construction increasingly used across Australia’s industrial and commercial sectors, as well as residential projects.
Valued by developers and contractors for speed, cost efficiency and durability, tilt-panel construction uses precast concrete panels to form the primary walls of a structure. As the name suggests, these panels are cast flat on site, then lifted or tilted into a vertical position and temporarily supported with props. From there, they are either bolted together or tied across the structure using roof beams between opposing walls, with anchors fixing the panels back to the ground to complete the structural system.
There are also applications that sit outside tilt-panel construction in a strict sense but follow a similar approach. For example, part-height precast panels, also referred to as dado walls, are often lifted into place, anchored to the ground and braced back to steel columns to form the lower portion of warehouse walls below sheet metal.
Gavin McPherson, lead engineer at Hobson Engineering, has seen first-hand why the method has gained traction across Australia.
“The biggest advantage of this method is the economics, and particularly the speed of construction,” he says. “Traditionally, you might be using steel cladding for the walls, fixed to steel girts. That means you need to erect the steel frame first, install the secondary support frame, sometimes adding extra battens, and then screw the sheeting on. With tilt panels, you are lifting a single wall element into place instead. That makes erection much quicker.”
For McPherson, that efficiency goes a long way to explaining the method’s uptake in recent years. Durability comes into it as well. Steel cladding often brings ongoing maintenance, whether through repainting or the replacement of sheets and fixings over time. Precast panels, by comparison, can be painted or left plain, and are designed for longevity.
Fasteners become critical in two main areas of tilt-panel construction, beginning with temporary bracing during erection, where brace anchors are used. Many of the components associated with precast panels are standardised under AS 3850. Hobson Engineering supplies brace anchors that comply with that standard, allowing panels to be temporarily restrained under high loads.
“You will usually see this where the precast panel is standing upright and angled braces run back to the slab or strip footing,” says McPherson. “Our anchors are designed for anchoring into slabs or footings in those situations.”
The company also supplies brace pins. The braces themselves are telescopic, with a smaller tube inside a larger tube and holes drilled through them so the length can be adjusted. The pin is used to set and lock the correct brace length. At the panel end of the brace, a flange bolt is typically used to restrain the brace back to a cast-in ferrule in the precast panel.
The second area is permanent structural connections. In this space, Hobson Engineering has introduced precast panel clips to clamp precast panels, or dado walls, back to steel columns, along with angle brackets used to connect panels at corners, either panel-to-panel or back to other structural elements.
“Precast has been on our roadmap for a long time,” says McPherson. “Over time, we have built the confidence to offer these solutions, continuously expanding our range. When we bring a product to market, it is because we are confident it complies with all relevant standards and meets the performance objectives it is designed for.”
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This conviction is vital in such a safety-critical application. Precast panels often weigh 10 tonnes or more, and any failure in connections can be catastrophic. McPherson points to an incident in Melbourne in 2005 as a reminder of what can go wrong.
“Something in the temporary restraint of the panel, whether it was the footing, the bracing at the base, or the fixings to the precast panel itself, caused a panel to collapse onto a Ford Falcon, completely flattening it,” he says. “It’s an example of the major damage that can occur, both to assets and human safety.”
Because of that risk, the restraint of precast panels is tightly controlled. AS 3850 specifically covers precast restraint, and authorities take a close interest in how these systems are designed and installed.
“There was also a case involving the bolts used to connect into the precast. Mild steel 4.6 bolts were originally specified, but they were changed to higher-strength 8.8 bolts. The tightening torque used was incorrect, and because the torque was too high, it fractured the ferrule in the concrete. When wind loads were applied, the connection failed,” says McPherson.
For engineers specifying fastening solutions for tilt-panel applications, compliance and verification should be key considerations. McPherson says confidence comes from knowing a product has been properly tested and performs as claimed, with clear alignment to the relevant requirements.
Hobson Engineering places particular emphasis on testing, especially where local standards diverge from international practice.
“For example, a lot of effort went into the testing we carried out on brace anchors to meet the Australian standard,” adds McPherson. “That standard is specific to Australia and does not really exist in the same form internationally. Even where overseas products appear similar, and in some cases may even be the same product, the testing requirements are different to what international suppliers are typically familiar with or have tested their products against.”
He believes responsibility sits with everyone across the supply chain, with no single party able to treat compliance as someone else’s problem. As a supplier, Hobson Engineering’s role is to provide the correct, compliant products.
It also sits with purchasing teams, site teams and the engineers who are designing the systems and checking the installation. Everyone involved needs to understand what is being used on the project and make sure it is suitable for the application.
In precast, McPherson acknowledges that differentiation is not always obvious. Many suppliers offer similar components, which can make the market difficult to navigate. Hobson Engineering’s response has been to focus on practicality, making it easier for customers to source compliant precast components alongside the rest of their fastening requirements.
“Growth has been a big focus over the past 12 months, particularly around expanding the range,” he says. “We have moved into areas like collated screws, made a push into lifting, material handling and load restraint, and precast is the next area of focus.”
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