Entered into the LSAA 2016 Design Awards (Cat 4, Large Fabric Structures #4114)

Entrant: Fabritecture (Designer and Installer)

Location: The Esplanade.   Completed: 2016

Client: Scentre Group (Westfield)

Team:  Scentre Group (Westfield), Wade Design, Textile Fabrication Services, Fabritecture 

 Application

Statement architectural fabric structure with complex steel geometry and state-of-the-art LED lighting system as part of a $670 million redevelopment of Pacific Fair Shopping Centre on the Gold Coast.

Description

The project was part of a $670 million redevelopment of the Pacific Fair Shopping Centre. Our project scope involved the complete design and construct (steel and fabric) of an architectural feature roof to cover the resort area of the shopping centre.

The project was designed to be a key architectural feature for the resort area of the Pacific Fair upgrade. The resort roof provides a functional weatherproof aesthetic feature that covers the first level promenade while leaving the ground level centre open creating a bright and airy space. 

The structure is located at the Pacific Fair Shopping Centre in Broadbeach on the Gold Coast.

Design Brief

The purpose of the project was to develop Pacific Fair as the ‘crown’ shopping centre on the Gold Coast. Pacific Fair is now home to the most uniquely innovative architectural fabric structure on the Gold Coast.

The client requested the fabric structure to be a statement feature to the resort area with a dia-grid style roof and lots of curvature as the main design principles. Angled Y columns required specific locations relating to shop fronts. The latest paint system, Quantum FX was also applied to the columns

The fabric was required to be highly translucent, as the area below needed to have a bright, airy ambiance whilst still providing shade and weather protection and longevity with low maintenance.

Structural System

Geometry: We were involved in the design of this project in the concept stage in 2013. From the outset, the Westfield Creative wanted to push the boundaries of the geometry. To explore different options, the geometry was modelled using Grasshopper Parametric 3D modelling software. Two options were finalised, being the Wave Orthogonal and the Wave Diagonal. Fabritecture completed preliminary engineering on the fabric and provided advice on the build-ability of each design. The Wave Diagonal was deemed to be beyond the boundaries of steel fabrication possibilities and the Wave Orthogonal was selected. This design comprised of the following:

• Outer Perimeter 3D curved edge beam - 363m long
• Outer Edge 3D curved edge beam - 265m long
• 80 curved rafters spanning from inner to outer edge
• 316 Struts connecting the rafters in 4 rings
• 198 Diagonal struts to create the dia-grid
• 18 Full height Y columns supporting the inner and outer edges
• 19 other support points around the outer edge comprising of 1-3 support struts

By far the most complex challenge geometry wise is the inner and outer edge. These are created using a large number of tangential curves (40 for outer edge and 41 for the inner edge) which, when connected together, create the undulating curved geometry required. The entire structure was modelled in Teklar and AutoCAD and then fed back into the clients master revit model to do a final check for geometry and clashes. Fabricating the steelwork for the roof posed a major risk for the project. To overcome this challenge, the entire roof - excluding column - was trial assembled during fabrication in sections. Each section was surveyed after trial assembly, and cross-checked against the theoretical geometry using the 3D model.  After fabrication, the steelwork was painted and then loaded into purpose-built cradles for freight to site. The 200 tonne of steel was delivered to site to match the installation sequence in 27 cradles.

• Patterning: The architect required that the seams in the roof match with the steelwork ring beams. To achieve this we used 9 concentric seams lines that were aligned parallel with the struts connecting the rafters. This resulted in 10 patterns per bay with a total of 790 different patterns.
• Details: The architect did not want to see any connections in the steelwork throughout the roof. The only allowed visible connections were pinned connections at the base of some outer struts. To meet this requirement all connections were designed to fit within the overall shape of the member and then sheet metal cover plates were installed to conceal the connections. Approximately 1,400 cover plates were installed in total.
• Drainage and Guttering: 300 half round gutters were to be installed on the inner and outer. This posed a challenge because 300 half round sheet metal cannot be rolled. To overcome this, the gutter was fabricated in approximately 900mm lengths that join of a gutter bracket, creating a faceted gutter. A best fit method was used and each gutter section was 3D modelled and shop detailed. Each section is a wedge shape in plan to allow for the change in angle at each bracket. The gutter feed water into downpipes which are fabricated and concealed within the columns that are plumbed directly into the stormwater drainage system.
• Installation Method: Particular emphasis was placed on the installation being perfect due to the resort roof being a ribbon ring structure. There was a highly technical process followed during the installation of the steelwork to ensure that structure met at the join accurately to complete the ring. To achieve this, all lifts, connection points and landing points (i.e. columns and base plates and primary lifts) were carefully surveyed prior to being put into place. The edge beam was also surveyed throughout the whole build to ensure a successful join. The install team were very particular to be sure the process was followed throughout the install. The end result was very satisfying with only 2 struts being half a bolt hole out. An intricate temporary bracing system was provided as an engineering solution to assist the install. This was required for all of the columns to control where the structure was positioned during installation, but before completion. This limited the dynamic movement of the structure during installation.
• There were a lot of other trades sharing the same site with limited access as the site was basically enclosed by the existing infrastructure of the shopping centre. This made an already complex installation methodology even more complicated.

Materials

Chukoh FGT-600 PTFE was the chosen fabric for the resort roof. PTFE was the preferred fabric as it offered the necessary translucency and longevity, and paired well with the LED lighting system. Tensile strength and a 20 year manufacturer’s warranty were also factors.

Fabrication

A complete trial assembly of sections was provided in the factory prior to installation. This was primarily due to the extreme complexity of the technical geometry of the steel.

The paint system on the steel is a Dulux Quantum FX protective coating, providing a metallic finish with a semi-gloss coating.

• Diablo connections and cover plates
• Lighting system and hydraulics

Collaboration

An integrated fall arrest system has been incorporated into the design of the roof structure for inspections and maintenance systems as required.

The resort roof is 5,400m² and took approximately 11,000 man hours to complete.

Cost and Conclusion

The Pacific Fair Resort Roof project is valued at AUD$4,000,000

The final steel link-up was almost perfect at only 7mm out, which was an incredible success for the installation! The client was very happy with the outcome. The project exceeded the needs of the brief, and resulted in being awarded another million-dollar shopping centre redevelopment project with the client.

The resort roof incorporates a state-of-the-art LED system capable of illuminating the structure in both solid and alternating colours. There is also a flowing gutter system to the edge beam that follows the system on both sides. The project exceeded the needs of the brief, and resulted in being awarded another million-dollar shopping centre redevelopment project with the client.

Ref: sliders/DA2016/Cat4/4114 DP ID 231