Tiger-Strong Materials

Designers of a new tiger enclosure have employed the latest in metal-mesh technology to keep wild animals at a safe distance, yet close enough to smell.

In the past, many exhibits at zoos were prime examples of the ‘starchitecture’ of their day. The Zoological Society of London (ZSL) is home to a number of celebrated buildings that house animals with the architecture and visitor as the clear beneficiaries. Famous modernist architect Berthold Lubetkin’s penguin pool for example, with its playful, iconic penguin slide, is among the many well-known structures at the ZSL that are of architectural interest but have struggled to adapt to modern animal welfare standards – as the goofy antics of penguins on a concrete slide attest to. But today, with many habitats and species facing extinction along with animal welfare concerns coming to the forefront, the focus has shifted. Where once the brief for a new animal enclosure might have focused on creating an architectural masterpiece, the focus is now on fostering the best possible environment for animal husbandry, welfare and conservation with the architecture and engineering delicately balancing these essential considerations against the experience of the visitor and the realities of an urban setting.

The ZSL’s new tiger enclosure began with the development of a brief for a Sumatran tiger habitat that includes tropical foliage, heated rocks, tall trees and high feeding poles for climbing and a custom-built swimming pool. One of the most important aspects of the brief is the requirement that the enclosure covering 2500 square meters of exterior habitat is transparent. The transparency of a tiger enclosure is certainly for the benefit of the visitor wishing to view the tigers. But more importantly, the transparency of the enclosure allows the tigers to have access to an expansive, outside territory. In this exterior territory, the tigers will be able to carry on with the activities they are accustomed to in the wild, such as surveying the horizon. Except of course that the realities of this urban zoo mean the horizon happens to be the vast expanse of prime real estate otherwise known as Regent’s Park.

The ZSL’s brief was entrusted to Wharmby Kozdon architects in collaboration with structural engineers Dexter Associates and specialist subcontractor Base Structures. The resulting enclosure is a nearly transparent, free-form roof that is a feat of engineering, design and materials science. It is made possible by new computer technologies that are capable of calculating complex geometries as well as an ultra strong and ultra lightweight mesh material called Woven 316 Stainless Steel Mesh, or simply ‘Zoo Mesh.’ Unlike a standard square-shaped mesh that hangs straight to assume its dimensions, Zoo Mesh is a rhombus-shaped weave that is able to distort in both horizontal and vertical directions. Like the fabric of a dress, this mesh is pulled tight in tension to accommodate the organic shapes of the proposed enclosure’s footprint. 3D computer calculations and modelling technologies made it possible to ensure the mesh achieved its required strength while minimizing the dimension of the mesh’s stainless steel wires and maximizing its aperture opening. The resulting stainless steel wires of the mesh are 3mm in diameter with a remarkably open aperture – or gauge. The combination of thin wires and an open gauge results in a mesh that looks like a nearly transparent net, draping to accommodate the complex, organic shapes that flow beneath. But at the same time, this mesh is immensely strong. It is able to withstand both the full impact of its inhabitants (an average tiger exerts nearly 500 kilograms per square centimeter) and 100-year weather conditions including snow loads.

The mesh supports the four poles that hold the structure, which reaches 17m in height in order to provide plenty of climbing opportunities for the tigers. Without the mesh, the poles would fall down (and vice-versa of course). Specialist subcontractor Base Structures had the large pieces of mesh cut to fit like the fabric of an enormous dress and brought to the site. They were then stitched together with the same 3mm diameter wire they are made of. The mesh is ultimately held in tension by the poles, which are simply pushed into the ground. In certain places, the remarkably open gauge mesh is all that keeps human and animal apart. In other areas, the mesh connects down to timber and glass, allowing visitors to come face to face with the tigers.

We think this metal mesh material is fascinating not only for its flexibility and strength but also for the architectural statement it makes. In this case, the material strives to accommodate the animal, creating a modern enclosure that is responsive to the natural behaviors of the Sumatran tiger. The material allows the architecture to literally – and justifiably – become almost invisible.

Sources:

Photo Source: © ZSL London Zoo. For more information about Tiger Territory, please visit: www.zsl.org

For more information on Base Structures, please visit www.basestructures.com