High-Performance Tower in Australia

HIGH-PERFORMANCE TOWER IN AUSTRALIA _______ Close-up view of facade Shelf panel 7500mm Exoskeleton columns Vierendeel truss Aluminium carrier frame Laminated glass lites Facade typical panel Substructure diagonal columns Exoskeleton columns 7.5m 1.25m 1.25m 9m Substructure diagonal columns Exoskeleton columns Facade typical panel Superstructure slab Balcony Exoskeleton Office Type C - Landscaped park Superstructure column High rise core Office Type A Low rise core Hybrid timber high-rise structure The building design is driven by a desire to reduce the embodied carbon targeting a 50%reduction fromamore typical construction on the same site. To achieve this, it looks to maximize the use of timber within the current compliance environment for a construction start next year. Thirty-two of the thirty-nine stories will be formed from glulam and CLT using both panelized and framed construction timber structures. The tower design uses a concrete core for stability and strategically uses a steel frame exoskeleton to support fire separating levels that divide the timber elements structurally into eight independent timber neighborhoods of between four and seven stories. Low embodied carbon specification of both concrete and steel will be pursued as the design develops. Setting the target for reducing embodied carbon Calibrating the embodied carbon performance has required establishing a baseline for an equivalent typical construction. This baseline is defined as a reinforced concrete framed tower, representative of the Sydney construction market and meeting the challenging client brief and the same site condition. This has set a starting point of approximately 865 CO 2 -eq/m² GFA from which the 50% reduction target was calculated, setting the challenge of 430 CO 2 -eq/m² GFA. Using mass timber The project looks to maximize the use of mass timber in the tower replacing conventional concrete floors with timber. The office space of the habitats will be constructed with a mass timber structure consisting of glue-laminated timber beams and columns, and cross-laminated (CLT) floors. Timber elements are part of the architectural design andwill be kept exposed internally mitigating the need for carbon-heavy finishing materials. The timber structural grid is designed with consideration for efficient transportation and installation. The habitat structures repeat up the tower bringing fabrication efficiency. As the design develops consideration is being given to connection detailing with a view to future demolition and to the durability of the timber frame. Fire engineering is an important consideration for the structure as a whole but especially given the timber component of the tower. Each timber habitat is FRL 90 and divided from adjacent habitats by mega floors of FRL 120. Reducing embodied carbon in concrete through specification Followingtimber,concreteisthenextbestmajorstructuralmaterial in terms of embodied carbon available in Sydney. Its constituent components are locally sourced and cement alternatives are developing in the market. Concrete is used for the tower’s core, the slabs of mega floors and the basement levels. Both their design and specification are done with embodied carbon in mind. The project team has researched the available concrete options, both in-use and in current development. Concrete specification is driven by design and construction requirements: whilst minimizing embodied carbon, the material must maintain a high early-age strength, key for jump forming the towers central core and must achieve long-term high strengths required to resist the large vertical loads at its base. The buildings substructure – a two storey basement and concrete podium – uses post-tensioning, fairly uncommon in basement slabs, to reduce the concrete and reinforcement volumes at these levels. Embodied carbon comparisons on a number of the main structural elements of the project has shown that concrete filled steel tubes have lower embodied carbon than steel only elements and are used for this reason. Procuring low-carbon materials A considered procurement approach is part of the project strategy for embodied carbon reduction. The production of steel in Australia is particularly carbon-heavy due to the energy used to power steel production plants originating from coal fired power stations. An assessment of alternative steel procurement routes worldwide was carried out to identify more sustainably produced options in countries like Korea or Germany where the carbon footprint of steel is less than half of Australian steel. Recently, first international steal producers are claiming to decarbonize their steal production in Australia by shifting tomore renewable energy powering electric arc furnaces, probably allowing the project to source greener steal locally. With about 8,500 cubic meters of CLT and 3,500 cubic meters of glulam, the project hopes to boost the Australian mass timber market. The design team has been assessing the transportation and sustainable forestry difference between larger European timber suppliers and smaller Australian suppliers. A combination of suppliers looks likely. Tracking embodied carbon in the design The tower’s embodied carbon is tracked through the design process and has been an important consideration for the project team on both large and small scale decision making. The embodied carbon is tracked directly using Building Information Management (BIM) modelling and collecting materials quantities using embedded data. _______ Simplicity and efficiency The mega frame is supported by a central core and very few isolated columns built as concrete filled steel tube, speeding up construction programme while providing a robust and fire-resistant solution. Mega columns run all the way down passing through the mass timber habitats. _______ Low carbon mass timber frame The office space of the habitats will be constructed with a glue-laminated timber frame and cross-laminated (CLT) floors exposed internally creating a low-carbon and pleasing environment. Timber frames are designed for disassembly and re-use, ensuring a long-term carbon sequestration. _______ Concrete core and basement levels _______ Steel mega frame _______ Timber habitats and exoskeleton _______ Facade support by exoskeleton _______ Facade framing flat arrangement _______ Facade framing curved arrangement The facade concept was developed aiming to create comfortable indoor environments for Atlassians with sustainability inmind. Creating naturally ventilated spaces for comfort and wellbeing was a key driver which led to a typology that allows to negotiate and optimize several ambient parameters such as daylight autonomy, thermal comfort, glare, and shading, all of which influence the overall energy demand of the building. The energy concept with its gradient zoning is addressed by a layered approach to the building envelope. This allows to achieve occupant comfort with natural ventilation through the office facade and a buffer area between the outer and the inner envelope in the park spaces. The outer facade in the parks functions as a barrier for rain and wind, whilst the inner facade to the meeting and workspaces forms the functional thermal envelope. Based on the unique structure of the building, which results in a multi- storey atrium space at every habitat, providing the opportunity to bring nature and the related comfort into this office building, the facade has to be supported from the exoskeleton to avoid additional substructure. Continuingtheconsciousnessaroundtheuseofresourcesintotheenvelope design, the structure is integrated into the facade which supports itself between exoskeleton columns. Each facade unit functions as a Vierendeel truss, using both the three-dimensionality and the height of the panel to be structurally very efficient and reduce the use of material leading to a reduced carbon footprint compared to more conventional approaches in which substructure and facade are separated. The geometry also forms a shelf which provides passive shading and allows for the integration of photovoltaic panels. The diagram is reporting numbers for scope Cradle to Gate (A1 to A3) for one of the evaluated scenarios for SSDA submission. The process of reducing upfront embodied carbon emissions for the Atlassian Central project has three parts which share their logic with the standard sustainability concepts hierarchy knowas “Avoid-Reduce-Reuse-Recycle”. Baseline. Unique site constraints make it unreasonable to compare the Atlassian Central projects against standard commercial tower structures in Sydney. A baseline building reflective of the project’s constraints was considered – sited above a retained heritage building next to a train station – requiring a raised first floor and a transfer structure. Estimates of the Baseline at this stage put it around 850-875 kg CO 2 -eq/m² GFA. Design. Embodied carbon is reduced through design decisions on material selection, substitution, or avoidance. Changing habitat floors from concrete to mass timber offers a significant reduction, by locking carbon into the structure and avoiding the use of emissions-intense steel and concrete. Such design initiatives have reduced the upfront embodied carbon to around 650-700 kg CO 2 -eq/m² GFA. Material procurement. Embodied carbon can be significantly reduced by adopting a considered procurement strategy, key to achieve the 50% reduction target. As an example, Australian steels have an embodied carbon two to three times higher than steel imported from other parts of the world having a greener grid, newer and more efficient smelters and higher recycled material content. Procurement optimisation could put the upfront embodied carbon emissions at around 300-350 kg CO 2 -eq/m 2 GFA which is tremendously low for a project of this kind in this location. _______ Embodied carbon analysis _______ Sustainable facade design _______ Hybrid Structure: a solution for mass timber in high-rise A steel and concrete mega-frame with podium floors every four stories provides the primary structure, and a fire compartmentation between the habitats. Mass timber floors installed in between are treated as independent 4 storey buildings from a fire perspective. _______ Functionality of external envelope _______ Typical habitat axonometric partially exploded “We have developed an innovative new approach to designing tall towers using a hybrid structure where the volumetric mass is timber. This approach significantly reduces the embodied carbon of the tower by up to 50% when compared to traditional tall building construction, setting a new sustainability standard for tower construction in the future.” ____ _______ _______ __________ EOC Co-founder and director James O’Callaghan “What excites me most about the Atlassian Central project is that the client, as owner-occupier, has been unconstrained by the usual industry benchmarks and they’ve set big hairy audacious goals. In particular, the target to reduce upfront embodied carbon emissions by 50% is industry leading for a high rise tower of this kind and requires innovation that hasn’t yet been seen in the market. The property industry is quite sophisticated and has been able to get their head around net zero carbon when it comes to operational energy but net zero carbon materials are a new frontier; the next and necessary phase of decarbonisation and I’m thrilled to be working with Contractors and Suppliers that are innovating in this space” ____ _______ _______ __________ LCI Principal, ESD, Matt Williams STRUCTURAL CONCEPT, MATERIALITY AND EMBODIED CARBON