The Russell B. Aitken Seabird Aviary, Bronx Zoo

The Russell B. Aitken Seabird Aviary at the Bronx Zoo had been in existence for more than a hundred years when in the early spring of 1995 the old building collapsed as its steel-pipe structure failed under the weight of an unusually heavy snowfall.
The Wildlife Conservation Society voted to commission a new aviary, which would be based on the existing site, emphasizing a program design that would be thirty percent larger, more interesting to visitors, and more conducive to the requirements of its permanent inhabitants - the birds.
To maintain historical continuity and make the most of existing features, much of the old false rock work was incorporated into the new design, as were the mature, dense trees that surrounded the site. The 3,000-square-meter building is situated within a sinuous, concrete perimeter wall that in parts is submerged below ground, though it emerges at each end to accommodate cave-like entrances. These are important design features that maintain the illusion, despite the enclosing mesh, of a completely unrestrained external environment. The achievement of this design requirement has been assisted by the specification of an extremely fine- one-millimeter-diameter wire rope, which has been woven into a 25-millimeter grid.
Though the new building is both visually and environmentally transparent, it had to resist snow loads and wind loads. The net is supported by 300-millimeter-diameter steel arches, two of which spring from a single base forming a diagonal pattern on plan. The net acts in unison with the supporting arches using double-curved shapes to provide a rigid structural system.