Entered into the LSAA 2007 Design Awards (3837) Project Category Cablenets
Entrant: UFS Australasia Pty Ltd
Client: Sydney Attractions Group
Architect: Misho & Associates/ RIHS Architects – Misho & Gerry Rihs
Structural Engineer: Fabric: Wade Consulting - Joseph Dean,
Steel: S2 Corporation Murray Allen Fabricator(s): Fabric Shelter Systems Graham Griffin
Application and Function:
Located on the eastern side of Darling Harbour the recently opened Sydney Wildlife World adds an iconic landmark to the Darling Harbour foreshore. The urban zoo is an extension to the facilities at the Sydney Aquarium. The wildlife park has been created to accommodate Australian wildlife in as natural an environment as possible to give short stay Sydney visitors exposure to the unique Australian fauna and floor.
The function on the tensile roof structure designed and constructed by UFS was to:
1. Create and Architectural Focal point as specified in the design brief
2. Contain the animals (mainly birds) within the buildings open air upper level exhibit area
3. Keep rodents such as Rat out of the exhibit areas
Design Brief
The architects design brief was to produce a building that would attract attention and excite the imagination, curiosity and emotion about what was inside, while complementing the Sydney Aquarium. The inspiration for the roof structure was from an organic arch but the inspiration on how to achieve it was drawn from the skeletal frame of a python. During the design phase Misho saw the skeleton on a visit to Sydney’s Taronga Zoo. Observing the python’s skeleton, Misho reflected on the way the snake’s frame was flexible enough to accommodate a swallowed kangaroo and, once devoured, return to its original size.
UFS’s design brief was to take the Architect unique concept and make it work incorporating the following design points
1. The unigue roof shape as drawn by the architect was to be maintained - every arch was a unique parabolic curve
2. The steel frame was to be as light weight as possible to minimize the visual impact
3. The steel frame was to be supported horizontally by a grid of near invisible stainless steel cables, no structural steel ties between arches allowed
4. The entire roof structure was to be cladded with a tensioned very fine woven stainless steel mesh that to our knowledge had never been applied to a tensile structure project.
Once UFS was contracted to design and construct the roof UFS’s design team put the wheels in motion in order to determine the best way to detail and build the project. Below is a list of the key design tasks and solutions UFS conducted and brought to the project
1. UFS Commissioned Robert J. Roy BE MengSc PhD MIEAust CP RPEQ - Consultant and Educator to determine wind drag co-efficients of the Zoomesh by testing it in a wind tunnel
2. Once the drag coefficients were determine UFS was able to offer the client a clear span design deleting the previously documented internal tree supports, this was a major advantage for the client and the overall design of the project
3. UFS conducted detailed stretch testing of the mesh to determine the required compensations for patterning
4. UFS undertook extensive research into the best way to fabricate tension and fix the Zoomesh to the steel frame.
5. UFS built a full scale prototype of a section of the roof for viewing and approval from the client and architect
Structural Systems
Method of Arriving at Final Solution:
Over a 6 month period numerous design meetings, extensive testing and prototyping took place in order to arrive at the final structural and detailed solution
Design Loading:
Design loads in accordance with AS1170 - plus point loads every metre along the under side of each arch able to support 1.2kn for a rope access worker
Ground Conditions:
Ground conditions were not applicable to the roof structure as it was attach to the top of the 1st floor external walls. We had to work to the geometry and RL’s governed by the building below
Geometry:
Geometry was a major design issue that took a long time to resolve; the reason being was that the initial 3D geometry was formed using parabolic curves for each of the 35 unique arches. Structural Steel can not be rolled to form a parabolic curve; instead sections of steel with differing radius’s had to be used. UFS carefully re-modeled the roof frame using straight sections at the beginning and end of each arch and sections with differing radius’s to form the shape of the roof.
Structural Systems:
1. Arches constructed out of CHS tube diameter 219 and 273
2. Arches are connected using a machined Diablo connection with a cover plate fixed to make the arch seem continuous with not connections
3. 316 Stainless guy cables provide the structural support for each arch terminating at each end of the structure into the concrete support structure
4. Custom Alu extrusion used to fix each fabric panel to arches
5. Membrane plates and catinery cables at the end of each mesh bay
Materials
Structural Steel Frame - CHS steel Arches were used as provided the most efficient material to span the required distances and aesthetically are pleasing.
316 Stainless cables swaged onto 316 fittings were used for there resistance to corrosion and tensile strength
316 Stainless membrane plates used for there resistance to corrosion and strength
316 Stainless Zoomesh was used as it was a nominated product nominate by the architect,
Custom Alu Extrusion anodized to 20um clear
Custom Made Keder out of Europe was using to provide the required warranty under the contract
Fabrication
Zoomesh Fabrication: The roof sheets were patterned from electronic geometry, each subpanel cut to size using a plotter, sewed together, custom Keder fitted then rolled onto a core for freight and ease of installation
Construction and Maintenance
Construction:
Installation was an incredibly complex operation that required both coordination with the
main building contractor and coordination with the contractors fitting out the exhibits.
Each arch was lifted into position in sequence with the tress that weighed up to 10 tonne.
Maintenance:
The maintenance required for the roof structure is very minimal as the 316 Stainless mesh
lets the water through and dirt / dust does not sit on the mesh. The steel is hot dip
galvanized, linished, wip blasted and coated with a high build polyurethane coated that is warranted for 15 years, therefore also requires very little maintenance
Costs: Approx $1.7M
