ARCH7162
BARANGAROO TOWER T WO
STRUCTURES AND CONSTRUCTION HIGH RISE ASSIGNMENT BEN ALLEN z3420517 HAYDEN CO‘BURN z3377204
TABLE OF CONTENTS
EXECUTIVE SUMMARY
PAGE 5
WHO/WHAT/WHEN
PAGE6
WHY BARANGAROO?
PAGE 7
HISTORY
PAGE 8
STRUCTURAL PHILOSOPHY
PAGE 9
FACADE SYSTEM
PAGE 10
TYPICAL FLOOR PLATE
PAGE 14
SERVICE INTEGRATION
PAGE18
STRUCTURAL IDEALISATION AND ANALYSIS
PAGE 20
EXECUTIVE SUMMARY This report has been undertaken to determine the structural philosophy, composition and assembly of Barangaroo Tower 2. The method of analysis begins with a qualitative assessment of the structural methodology and materiality employed in the project: progressing into a quantitative evaluation of the structural performance of the tower under nominated loads. The results are exhibited graphically to indicate the variation in stresses across an entire frame.
The report is limited in its scope and only attempts present an idealized structural assessment of Barangaroo Tower 2. The assessment is guided by an attempt to understand how the structural philosophy and performance is informed by the architectural design intent.
001. // WHO/WHAT/WHEN The Barangaroo precinct is an extension of Sydney’s CBD along the western foreshore at Millers Point. The site area of Barangaroo is 54 acres, which is divided into Barangaroo; South, Central and North. Barangaroo South will adopt the same scale, height and density as the existing CBD, it will host Barangaroo Tower Two. Barangaroo Tower 2 is one of three homogenous towers that will deliver approximately 320,000 sqm GFA of unique harbour front office space. Rogers Stirk Harbour + Partners designed the masterplan for Barangaroo, including the initial design of the three Barangaroo towers. Beyond the masterplanning stages Lendlease was engaged to collaborate with Rogers Stirk Harbour + Partners to ensure the project adhered to the relevant Australia standards and to assume the responsibility for documentation and coordination. The construction of tower two commenced in 2012 and has been completed in 2016. The Barangaroo masterplan will be continually implemented until the expected completion date of 2024.
ARCHITECT
ROGERS STIRK HARBOUR + PARTNERS // LENDLEASE
LOCATION
SYDNEY CBD WESTERN FORESHORE
TIMEFRAME
2009 - 2016
HEIGHT 178M
CLIENT
NSW GOVERNMENT // LENDLEASE
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BARANGAROO TOWER T WO 002. // WHY The decision to study and assess Barangaroo T2 was driven by the prominence and immediacy of the development. The Barangaroo towers were designed to achieve extensive sustainability targets whilst also focusing on maximizing the leasable GFA available, these factors coupled with the scale and economics of the project will inevitably inform the structural composition of the tower The Barangaroo towers are an interesting study in structure defined by economics. The towers structure needs to be designed to satisfy the construction buget whilst also permitting an expansive leasable floor area with minimal obstruction to views. Balancing cost and economic potential is a vital skill for contemporary high end architectural development.
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003. // HISTORY The name Barangaroo is taken from the name of a prominent Cammeraygal woman who played an important role in the relationship with British Colonisers in the late eighteenth century. Prior to settlement, the Barangaroo site and the great Sydney CBD area formed part of the territory of the Cadigal people, who are the traditional owners of the Sydney city region. The area was utilized for fishing and hunting for up to 15,000 years before European settlement. In 1900 the NSW government seized the Barangaroo site to develop shipping infrastructure to allow international trade. The site operated as a shipping port for over 60 years until the density of the city began to inhibit the ability to run heavy rail into the port. In 2003 the NSW government announced that the disused shipping port would be transformed into a new urban precinct. Subsequently in 2005 an international competition was held and won by Hill Thalis Architecture + Urban Projects, Paul Berkemeier and Jane Irwin Landscape Architecture. The concept plan was approved in February 2007.
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STRUCTURAL PHILOSOPHY The Barangaroo development has been conceived as a project that changes the way the residents of Sydney work, live and play with a strong emphasis on a public waterfront renewal program. Beyond the urban public spaces and sustainable design the Barangaroo towers are driven by the economic reality that almost all commercial development faces; maximizing leasable floor space and securing tenancy. The economic situation dictated the form and structure of the Barangaroo towers. The original proposal by Rogers Stirk Harbour + Partners called for two towers rather than three, however this meant each tower was significantly larger than the three built towers and was not compatible with the Australian tenancy market. The Barangaroo towers are marketed as having expansive floor plates, generous ceilings and commanding views. These characteristics are only possible due to the rigid core structural system and tapered columns that allow for an open, adaptable leasable floor plate with generous views. The design of the floor plates and positioning of the columns maximizes the daylight potential of each floor.
‘The prospective tenants did not want to consume that many square meters in one building. It was just too lumpy, too expensive and too hard to get away completely. There’s a whole lot of economics in it – if you’re in New York, maybe it is a different deal. But here in Australia 50 – 75,000 sqm is optimum for a floor NLA.’ - Graham Jones, Principal Architect at LendLease.
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FACADE SYSTEM The façade is the most visually striking element of the Barangaroo towers and serves to distinguish the three towers. The façade is designed to respond to the unique solar conditions of each aspect of the tower, considering the sun path, solar harvesting and diffusion opportunities to promote regulated natural light across the façade. Light was mediated through the use of blades, fins, sun shelves and louvers that vary relative to the solar requirements of the aspect. The façade consumed a large portion of the budget, diverse façade treatments that are fixed externally is a time consuming and costly exercise. The exposure to uninhibited winds demanded that the facades were given appropriate structural consideration to deal with the high wind loads. The curtain wall system is fixed into the cantilevered slab with rigid aluminum attached to provide stiffness, the slab is thickened at the edge to increase strength. \\ The façade also incorporates nano-technology, employing engineered glass with tints to improve clarity when exposed to sunlight.
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CONFIGURATION 1
For intense solar exposure, predominently on the eastern and western facades that recieve direct light at a low angle.
CONFIGURATION 2
Employed on the northern facade and at high levels on the southern facade.
CONFIGURATION 3
Predominantly used on the northern facade. The sun shelf repels direct northern sun which sits high in the sky.
CONFIGURATION 4
Allows ample solar penetration without direct light. Sunlight is directed into the ceiling and diffused.
CONFIGURATION 5
The open facade allows maximum daylight penetration and is only used in spaces that do not recieve a great deal of sunlight, such as the lower floors on the south side.
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RESPONSIVE FACADE SYSTEM The facade is diversified depending on the solar conditions of the aspect. Southern aspect recieves no direct sun and as such has the most permeable facade systems to maximise day light. The eastern and western facades recieve direct low sunlight and are fitted with the greatest facade protection.
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FACADE VARIATION The facade is not required to provide any structural benefit to the tower, beyond the given rigidity that it brings. The freedom of the facade allows for the intense diversity of facade treatments and allowed the architects to allign facade performance with the environmental and comfort targets of the development.
STRUCTURAL EXPRESSION The column and suspended slab structure with core allows for a structure free facade. The high strength concrete columns can achieve the same structural results with less visual instrusion. The columns taper as the floors increase to ensure the visual impact of the structure is not unnecessary or excessive.
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T YPICAL FLOOR PLATE
COLUMN AND SUSPENDED SLAB STRUCTURE WITH DUAL CORE CORE
COLUMN AND SUSPENDED SLAB -
The central core is concrete construction with 300mm planar concrete walls providing rigidity to the structure. The central core includes fire stairs and building services. The external core houses 43 lifts which service specific floors of the tower to reduce congestion.
The tower is supported by a column and suspended slab system. A typical floor plate is a 450mm pre-stressed reinforced concrete floor. Columns taper as the height increases. The ratio of the concrete also reduces at the top of the tower. Graham „ Jones, the principal architect as Lendlease commented that The bottom concrete is 100MPa but the top is pulled back to about 50MPa“. The cantilevers beyond the columns are restricted to 4m as to reduce the need for a beam which would add cost and time to the project.
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SERVICE CORE
1000mm DIAMETER COLUMN LIFT CORE
1350mm DIAMETER COLUMN
1500mm DIAMETER COLUMN
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PODIUM PLAN The podium level is an extended floor plan with a triple height clearance. The columns continue into the podium and provide structural support to the floors above. The extend floor plate and roof structure is supported by smaller column sections that run along the perimeter of the tower.
PODIUM SECTION
The core provides structural support for a number of gantrys. The column and suspended slab structure with dual core keeps the podium level rigid and carries loads down which allows the podiums perimeter structure to remain slender.
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SER VICE INTEGRATION The core that runs externally along the northern faรงade contains 3 banks of 8 lifts totalling 24 lifts and serve the three portions that make its height. The core that runs centrally within the floorplate configuration is divided into two flanking fire stair cores, and a dedicated service channel which houses all of the electrical and communication conduits, hydraulics, HVAC, exhausts and other services demanded of a world class high rise tower. An essential service lift also runs within this central core. The plant rooms are situated at the three hips that separate the building into thirds. This allows for external ventilation through louvre panels and cooling without unwanted exhausts on tenancy levels. The 16 compressors that power the services throughout the building are positioned in the basement, which further frees up any potential Net Lettable Area which was an important driver of the design throughout the project. An innovative solution to heat removal within the building, a liquid cooling system was integrated into the structural system (core and slabs) and circulates the surrounding cool sea water through the building, extracting unwanted heat from within, which reduces the demand of energy.
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SERVICE PATHWAY
CORE CONFIGURATION
Grouping the services has three benefits. 1. Services can be delivered more efficiently. 2. Frees up the remaining floor plate for leasable area with preferential views. 3. Creates a rigid core.
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IDEALISATION & ANALYSIS
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The Lift Core and Service core (which includes fire stair boxes) are idealised as shear planar elements, and as such are cross-braced to depict this. Large pilons are driven down 30m until hitting bedrock to anchor the tower and provide lateral support to resist high wind loads at 43 storeys. This large piling is also to hold the tower down, as the basements are excavated below the water table and acts as a tub which has a tendency to become buoyant. In discussion with John Carrick, we were advised to apply pin joint restraints where the pilings terminate and where they transition to columns at basement slab. These columns continue the height of the building and support large reinforced concrete floor spans and a cantilever of 4m, idealised as rigid joints. The columns diameter steps down at every third of the building from 1500mm through to 1000mm, to respond to the reduction in axial compressive load due to the static gravity loads. Due to the large diameter of the columns, in the discussion with John Carrick we were advised to idealise the columns as welded beams (1200WB455) to work in Multiframe.
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SECTION 1
SYSTEM
AXIAL LOAD
BEND
DIAGRAM
DIAGRAM
DIAGR
DING
SHEAR FORCE
DEFLECTION
RAM
DIAGRAM
DIAGRAM
ACTION EFFECT
LOAD PATH
DIAGRAM
DIAGRAM
COMPARISON OF CROSS-BRACED CORE The cross-braced core resists deflection by up to seven times compared to an unbraced-core, emphasisng its purpose beyond a shaft for services.
ACTION EFFECT
LOAD PATH
DIAGRAM
DIAGRAM
Concrete beams within the floor slabs are nominally 420mm within the column grid, however thin out to around 275mm at the perimeter to engage with the cantilevered ring beam which bears the structural façade elements. In discussion with John Carrick, our concrete beams and columns were translated to steel members to react more comprehensively within Multiframe; as a rule, the members’ depth was rationalised at 2/3rds to become a steel member. Therefore, the concrete beam of 245mm becomes 180UB22.2, while the concrete beam of 420mm becomes 250UB37.3.
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H
M
As can be seen from the section 1 deflection diagram, the tower experiences approximately 1000mm of deflection under a 4kN/m UDL wind load (combined with a 5kN/m gravity load). This load becomes more apparent the higher the tower reaches, and it is essential for a core to resist deflection. Without the rigidity of the core/s, the tower deflects around seven times as much.
SECTION 2
SYSTEM
AXIAL LOAD
BEND
DIAGRAM
DIAGRAM
DIAG
DING
SHEAR FORCE
DEFLECTION
GRAM
DIAGRAM
DIAGRAM
17.00.06.0 C:\University\Year 1 - Sem 2\ARCH7161 - Advanced Construction and Structures\160702 - Multiframe\Barangaroo_3D.mfd
Sections
250UB37.3 200UC59.5 180UB22.2 1200WB455 310UB46.2
Patch Material (No Material)
y z
x
NOT FOR COMMERCIAL USE
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REFERENCES
ONLINE http://www.barangaroosouth.com.au http://www.barangaroo.com/discover-barangaroo/ http://www.rsh-p.com/projects/barangaroo-masterplan/ http://www.barangaroo.sydney/about/history/ http://thehoopla.com.au/barangaroo/ INTERVIEWS Interview with Graham Jones, Principal Architect at LendLease
THANK YOU.
BEN ALLEN z3420517 HAYDEN CO‘BURN z3377204