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6 & 8 Parramatta Square Post-Tensioning and Load Transfer Systems

Delivering advanced post-tensioning solutions for one of Australia’s tallest commercial towers.

The 6 & 8 Parramatta Square development is a defining feature of the Parramatta CBD skyline — a 55-storey, 243-metre commercial tower forming part of one of Australia’s largest urban renewal precincts. The structure incorporates post-tensioned floor slabs and a complex outrigger truss system, requiring innovative engineering solutions to manage load transfer between the tower’s upper and lower levels during construction.

Interspan’s Role

Interspan delivered 700 tonnes of Strand post-tensioning across all 55 floor slabs, and both horizontal and vertical bar systems to support the outrigger structure.

Vertical bar post-tensioning: 57mm diameter bars installed through the outrigger zone.

Horizontal bar post-tensioning: 75mm diameter bars connecting outrigger beams to the building core.

To optimise program efficiency and site logistics, Interspan prefabricated reinforcement cages with integrated PT bars off-site, enabling direct installation on-site and reducing critical path time.

Additionally, Interspan supplied and installed 16 flat jacks (1,000mm diameter) to control and transfer loads from the upper levels into the outrigger beams, ensuring a precise and predictable load path in accordance with the structural design requirements.

This project showcases Interspan’s capability in delivering integrated design, engineering, and construction solutions for complex high-rise structures.

Project Details

General contractor:  Built Obayashi JV

Customer/Owner: Walker Corporation

Designer: BG&E

Work Period:  2019-2022

Solution: Post-Tensioning, Jacking works, Bar post-tensioning

GLOBAL LEADER IN SPECIALISED CONSTRUCTION SERVICES

Interspan delivers efficient, durable and sustainable solutions across bridges, tanks, buildings, ports and energy infrastructure — helping clients optimise structural performance, reduce costs, and lower embodied carbon in construction.

Our expertise spans post-tensioning, structural strengthening and specialised concrete technologies, applied across both new and existing structures.

By integrating engineering design, construction methodology and material efficiency, we deliver technically robust outcomes that enhance safety, service life and overall project value.

EXISTING STRUCTURES

External post-tensioning is a proven active strengthening method for upgrading existing structures, including bridges, buildings and tanks. It involves installing prestressing cables or bars outside the structural section, guided by deviators along the most effective load path.

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Replacing bearings and expansion joints is essential to restore performance and extend the service life of ageing bridges and civil structures. Upgrading these components restores the structure’s ability to accommodate movement, rotation, and stress, improving durability and long-term serviceability.

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Jacking and structural monitoring are both critical parts of any safe load transfer process and require expert engineering guidance.

Interspan designs custom solutions for diverse projects where precision loading/unloading and monitoring of structural elements are required.

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Forensic services are often utilised to assess potential compliance issues between the approved structural documentation and
the built structure. We utilise both non-destructive and destructive testing methods to understand the composition of existing structures.

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Over the last decade, Interspan has developed proven epoxy-based, retrofitted Tendon Truncation procedures that ensure post-tensioned tendon forces can be safely transferred into the remaining structure.

Our teams have decades of experience with post-tensioned structures, and we know how and where to use truncations as well as how to install them safely.

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We have significant experience with structural grouting, and our pumps can mix and place proprietary grouts with or without cementitious or epoxy-based aggregate.

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Corrosion is one of the most common and expensive durability issues stakeholders encounter in both building and civil structures.

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We understand structures. We know why they crack and how to fix them. Our experienced teams design custom solutions to address any kind of crack that emerges. Typically, a crack is the symptom of a problem, not the cause.

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We promote innovative, proven solutions utilising various CFRP-based strengthening techniques depending on the nature of strengthening required for your project. Our knowledge and experience in this area are second to none, and we’re extremely proud of the work our teams do every day.

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We provide solutions for all types of concrete repair. Whether it is due to deterioration, carbonation, damage, or defective concrete, we put forward a remediation solution to ensure the section’s durability and strength are fully reinstated.

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NEW STRUCTURES

Innovative construction methodologies enable works to be completed outside the critical path in a safe and controlled environment. This approach reduces project costs and schedules, improves safety, and minimises disruption.

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Interspan has extensive experience in the supply and installation of post-tensioning works in bridges, using state-of-the-art equipment to apply uniform stress to the separate strands of the tendon simultaneously.

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Lifting and jacking operations are essential when prefabricated elements or existing structures need to be moved, raised, or installed with precision.

These techniques reduce reliance on heavy craneage, minimise risks, and enable construction in challenging environments or tight timeframes.

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Stress bar post-tensioning systems provide a cost-effective solution for applying post-tensioning forces to short, straight tendons without requiring any profiles.

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Through effective design, post-tensioned slabs enable material and embodied carbon reductions versus a conventionally reinforced slab, while maintaining the inherent benefits of concrete construction.

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