Barangaroo Cultural Centre, Sydney, Australia
How a range of Ancon shear load connectors and locking pins contributed to the build of the cavernous new Cultural Centre at Barangaroo Point, Sydney, Australia.
Lend Lease has installed 1,300 slab-to-slab connectors from Ancon in the suspended post-tensioned concrete floor of the stunning Barangaroo Cultural Centre in Sydney. Use of these products at the temporary movement joints, in place of traditional pour strips, has significantly accelerated the build programme, saving both time and money. The design uses a combination of Ancon DSDQ double shear dowels and Ancon ALP locking pins to accommodate the initial shrinkage of the concrete and then allow the joints to be locked preventing further movement, whilst simultaneously transferring high shear loads in both the locked and unlocked state without the need for additional mechanical supports.
Barangaroo Cultural Space
On the banks of the world-famous Sydney Harbour, the development of a landmark 22-hectare site known as Barangaroo is taking shape. On completion of this project, not all of Sydney’s iconic structures will be above ground.
Hidden below the surface of the new Barangaroo Point, will be a giant subterranean ‘cultural space’. Measuring some 140 metres long, 50 metres wide and 18 metres high, illuminated by skylights set into the landscaping above and featuring a dramatic sandstone cliff face along one full side, this breathtaking space will be available for multi-functional use.
As expected with such a distinct project of this scale, a number of engineering challenges have arisen. These include the design of the enormous suspended concrete floor of the void, which must not only be strong enough to withstand the demands of the completed public space, but also the weight of the construction activities involved in the creation of the colossal green-roof which soars above the void and will form part of the park itself.
The roof comprises 300 precast concrete bridge segments. Each segment is 30 metres long and lifted into position by a 450 tonne crane standing on the suspended post-tensioned floor slab.
Issues with Pour Strips
A key design consideration in any post-tensioned concrete slab, where long uninterrupted spans can be achieved, is the accommodation of normal concrete shrinkage. This has traditionally been accommodated by leaving 1 metre wide ‘pour strips’ or ‘delay strips’ in the slab. These strips are filled once movement has stabilised, typically 1-2 months after the first pour, providing the desired continuity to the slab.
Although common, these strips are not ideal, as they require the slabs to be propped from below. This restricts site access and delays construction work and follow-on trades both above and below the slab while the mechanical props are in place.
Benefits of ‘Lockable’ Connectors
Dowel Bars transfer load across joints in structural concrete and are used with a sleeve component to debond the dowel where movement is required. Ancon developed this principle further by engineering a dowel which could be locked after an initial phase of movement.
Ancon’s ‘Lockable' range was developed specifically for use at temporary movement joints in post-tensioned concrete. These products accommodate initial concrete shrinkage and are then securely locked, mechanically and chemically, preventing further movement taking place.
The original Ancon Lockable Dowel, launched in 2009, transfers shear load in both its locked and unlocked state while the Locking Pin, a recent extension to the Ancon range, is ideal for applications where tension loads are high and there is a requirement for a joint to be locked but the shear load can be accommodated by other means.
On the Barangaroo cultural space, Ancon Locking Pins were used in conjunction with Ancon DSDQ double shear dowels; the first enabled the joint to be quickly and cleanly locked after movement, while the latter carried the high shear loads without any requirement for additional slab supports. Together, these products provided the quickest, safest and most cost-effective solution for this unique application.
Aaron Blanchard, Lend Lease Project Engineer, said:
Prior to Ancon’s involvement, our design was for a delay strip. This design would have slowed us down as we had a set date to install the roof. By using Ancon’s products, we were able to eliminate the pour strip, and saved time on our program. We were able to accelerate the program by 50-60 days, which obviously also has significant financial implications.
Locking Pins comprise a pin and a sleeve component. The pin is manufactured from coil bar; one end features a hot forged head which increases its resistance to tensile forces and the other end features a notch to accept the Ancon locking plate. When installed in the heavy duty injection moulded L-shaped sleeve, the pin is cradled to ensure even distribution of the high strength, cementitious, non-shrink Ancon grout poured from the top of the slab. The sleeve is ribbed on the outside for increased bond with the concrete and features indentations on the inside to maximise grout bond.
The Ancon DSD is the original two-part, double dowel, high load shear load connector; specific to the ‘Q’ version used here, the dowels fit in cylindrical sleeves contained within rectangular box sections to provide movement in two directions.
Both products allow some lateral and rotational movement in addition to longitudinal movement in the initial phase.
Installation & Performance
Reflecting on this part of the project, Lend Lease Site Engineer, Mike Cummins, said:
We’ve had no problems with the slabs. They stood up to the weight of the cranes during the roof installation and we’ve had plenty of trucks on them since with no adverse deflections. For our purposes it worked exactly how we wanted it to and locking the joint up was really quick and clean.
When it opens to the public in mid-2015, Barangaroo Point will provide an attractive new vantage point from which to take in the atmosphere of Sydney Harbour, while the awe-inspiring cultural space below, with a floor area of up to 20,000 sqm, will provide the flexibility to house almost any future event.
Concrete structures are designed with expansion and contraction joints to allow movement to take place.
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