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. The project began in February 2019 and finished at the end of October.
The Westpoint Shopping Centre had to remain open, which meant the principal contractors – Construction Control (construction Company) – 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 structural props consisted of structural members to support loads during construction. In this instance structural back propping was required to support the permanent structure whilst the rectification works were undertaken. 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 principle contractor needed a solution that could be installed quickly so the project could be completed within scheduled time.
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 whilst 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 Baulch. “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.”
Baulch says Construction Control contracted Coates Hire to design a propping solution, and to also prop a shear wall with a lateral brace before any work could begin..
The lowest level of the parking building needed six100-tonne for each column and the propping ratio reduced at each storey.
Baulch says the Westpoint parking building remediation was an engineering-intensive exercise, and the Coates Hire team demonstrated their value in its ability to formulate solutions.
“Remediating is also more complex than construction,” says Baulch. “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 Hire 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.”
Mark Hutchison, Coates Hire Engineer – Temporary Works, says the parking building remediation project was all about safety and efficiency – the columns had to be rectified so that the car park could be re-opened as quick as possible to limit the impact on the business owners and reduce the negative impact on the wider community that used the shopping centre. .
He says 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 3rd floor down through the props on each floor into the building footings/underlying strata “The structure had to be made safe for customers while the works were completed,” says Hutchison. “The car park was being used by shoppers while it's being repaired.”
Coates Hire 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.
Hutchison also states that based on the exceptional work undertaken by the Coates Hire Services installation team, lead by Installation Manager, Neil Gujare, Coates Hire Services also secured the Block 2 installation works which consisted of propping a further 62 columns, requiring approximately 1736 props.
Hutchison says that with so much hire equipment required, and such a delicate job while the car park remains operational, Coates Hire was a perfect fit for the project and 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 Hutchison. “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.”
He says the project numerous stages of rectification work, most of it requiring tailored solutions.
“There was nothing off-the-shelf about the project. There was a lot of small, niggly problems, which is a normal challenge for rectification work.
“It’s a good feeling knowing we have the specialist equipment, the expertise and reputation to create a safe work area for our customers.”
Kevin Baulch says the relationship with Coates Hire was one of partnership.
“The Coates Hire 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,”
Baulch says one of the lessons he learned from Coates Hire was the power of reviewing.
“Coates Hire 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.”
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