Coates delivers tailored propping for complex car park remediation

The project

In August 2018, the owners of Westpoint Shopping Centre in Blacktown, Western Sydney, found some anomalies with the columns in the car park of their building. The decision was made to strengthen 715 columns in the multi-storey parking building by removing the existing concrete and re-casing the columns with a higher grade of concrete.

Principal contractor Construction Control engaged Coates Engineering Solutions to design and install a propping solution, as well as prop a shear wall with a lateral brace before any work could begin. The project began in February 2019 and finished in October.

The challenge

The shopping centre had to remain open, which meant Construction Control had to work on one side of the car park while 300 car parks on the other side remained open.

This required the highest standard of structural propping, to ensure the building was safe for public use while it was being remediated.   

The decision was made by the engineers to prop every column in the car park building, even though propping every second column would have satisfied the load requirements.

The project required a large number of props to support every column, at every level, and the Construction Control needed a solution that could be installed quickly so the project could be completed within scheduled to limit the impact on business owners and the wider community.

The solution

Kevin Baulch, Senior Project Engineer at Construction Control, says the decision to prop every column was the right one, considering the scope of works and the fact that the public would continue to use the building while the works were being performed.   

This included stripping the concrete from the perimeter of the 1140mm x 300mm concrete columns, and replacing it with 1500mm x 600mm concrete columns, while also replacing the 40 megapascal (MPa) concrete with a stronger 65 MPa mix.

However, the decision to prop every column meant finding the contractor with access to so many props, and with a capacity to expertly install them quickly.

"We needed a total of around 2500 props, and not many organisations held that sort of inventory," says Kevin. "The Opal Tower problems had come to light in December, and that building required a lot of propping, so the expectation was that there wasn't a lot of stock around."

Coates was initially engaged to prop four columns prior to Christmas, with a further 18 columns added early in the New Year. This equated to the installation of 616 props, 1,584 timber sleepers and 220 Universal Column grillage beams. They were installed while working closely alongside other trades and under Construction Control's strict works program.

According to Mark Hutchison, Temporary Works Engineer at Coates, the columns could carry very little weight while they were being rectified, so the engineers required significant propping around each column, creating a load-path from the third floor down through the props on each floor into the building footings/underlying strata.

The lowest level of the parking building needed six 100-tonne props for each column and the propping ratio reduced at each storey.

The impact

Kevin says the Westpoint parking building remediation was an engineering-intensive exercise, and the Coates team demonstrated their value in their ability to formulate solutions.

"Remediating is more complex than construction," says Kevin. "There were several issues with the building and we needed more than just a lot of props and a professional installation.

"We needed a really tailored response and the Coates team helped us with design and solutions. They're engineers so we could work with them on how the trickier applications were going to work."

Based on the exceptional work undertaken by Coates' installation team, Coates Engineering Solutions also secured the Block 2 installation works, which consisted of propping a further 62 columns, requiring approximately 1736 props.

With so much hire equipment required, Coates was the only company capable of designing, supplying, installing and certifying such a large quantity of props within the time frames required.

"We have a lot of specialist equipment and we have our own qualified engineers and certification process," says Mark. "We can mobilise very quickly, so in jobs where serious loads have to be safely propped at short notice, the customer can rely on us."

Kevin says the relationship with Coates was one of partnership.

"The Coates team were prepared to work on problems, conduct the planning and come up with outside the box ideas. Both organisations learned so much from this project because of the way we collaborated.

"Coates review all of their work and their work processes. It ensures that everyone is learning and you all walk away knowing how to do the job better," says Kevin.

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