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Safeguard OSH Solutions - Thomson Reuters

Safeguard OSH Solutions - Thomson Reuters



Safeguard Magazine

Needles in concrete

An apparently simple solution required laboratory testing before it could be approved. Then it won an award. PETER BATEMAN reports.

Some clever design thinking early in a high-risk project’s life resulted in a world-first outcome which significantly reduced safety risk and increased productivity – a result which saw the project win the safety category at this year’s NZ Workplace Health & Safety Awards.

The project for the Fulton Hogan John Holland Joint Venture went by the name of the Wellington Traction Overhead Systems Renewal, which translated into English meant renewing the 80-year-old electrification of 35km of rail corridor in the Wellington metro area. The old timber masts carrying the infrastructure were to be replaced with steel reinforced concrete foundations and galvanised masts. The risks? Working around existing high voltage infrastructure, and working alongside freight and commuter trains. In other words, high risks.

Project manager Graham Bradley says the old method of creating concrete foundations was problematic. It involved placing reinforcing cages up to six metres in length into holes dug by auger, but there were issues with that traditional method: unforeseen ground conditions meant the cage provided was often unsuitable and had to be replaced with another of different length. Also, the process required an electrical spotter to observe, as well as a train spotter (yes!) to ensure the cage was not slewed into the path of an oncoming train while being lowered into position.

“Though we are off track there is a possibility the chain may break and the cage falls over. We have to stop work until the train is completely clear, and for almost ten minutes prior to the train coming.”

THE SOLUTION

During the design phase the team came up with another idea: using a relatively new form of steel fibre reinforcement and doing away with the reinforcing cage altogether. Bradley knew about the fibre because he’d used it in a project for his engineering degree ten years earlier at Monash University, where the competition was to make the strongest beam with the lowest weight.

“We were in the lab and it was the first time I’d seen these fibres. They have an amazing structural capability. We came second. Ours was the only beam that didn’t break. It’s a fond memory because it gave us a good result for the semester.”

As it happened the project’s consulting designer, from Wellington engineering consultancy Novare Design, had some experience of using the fibres in a house slab and was a big advocate for them. A design for a new foundation method was produced – “it’s like putting a bunch of needles into the concrete” – which resulted in a foundation of the same or better strength as the old method but without using the massively obstructing reinforcing cage, and could be delivered in a small bag to the concrete pouring truck. And then the real work started. How to get this new concept through the approval process?

“We believe it’s the first time it’s ever been done, for the railways and in that type of construction. That’s why it took eight months to get all the risk reviews and producer statements.”

A patient and supportive client – KiwiRail – and much collaboration was required to get the perfect solution that was easy to build and met all the structural requirements. Then, in order to get producer statements signed off, the team took the idea to the University of Auckland with templates and examples for testing.

“The independent design review was reluctant to sign it off because there was no case for it previously, so we got the lab tests to prove the numbers our designer had come up with.”

THE OUTCOME

Bradley says the new method has been fantastic for both safety and productivity. Man hours have been reduced by half, the machinery required has been much reduced, and all the risks associated with dragging around large cages next to trains and in a high-voltage electrical environment have been eliminated.

“It’s made the job a lot more streamlined. It’s a very good solution and we’re pretty proud of it.”

The new method even costs a little less. Each cage costs $500 to $600, while the new fibre-reinforced concrete costs around $100 per cubic metre, and on average each pole requires about 4.5 m3 per pour, so it makes sense economically even before taking into account labour savings. Bradley says the designer reckons the result is superior too, with a more durable and stronger foundation.

INTEGRATING DESIGN

Apart from the success of the method, Bradley says there is a further lesson to be drawn from the project: the importance of incorporating design thinking early in any construction job so that safety risks can be built out before work begins.

Most tendered jobs require a tender to be submitted in four weeks, which he says isn’t enough time to allow the design collaboration required to produce an excellent outcome.

In this case, the designer was running workshops with the Joint Venture team. “That’s where a lot of risks can be taken out. If you can get those two parties working together you can make all sorts of strides. Once you’re building it, it’s too late.”

He describes the solution as “out there”, and acknowledges the good fortune in having a client willing to embrace change and patient enough to wait while the new design was approved.

“The more time you can put in, the better. It just changes a lot of things and produces multiple outcomes.

“It’s value for money and a safer way for our workforce.”

PETER BATEMAN

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