However, the bridge wasn’t comprised completely of GFRP. Composite components serve as the primary structural skeleton, while a stainless steel mesh acts as the cage material that connects to GFRP. The 2 x 2-inch woven stainless-steel grid used for the gorilla habitat is a conventional material for zoo enclosures, Doudican says.
The floor and two mechanical doors also are made from GFRP. The floor needed to support the weight of a typical male gorilla. Mokolo, the only male at the zoo, is a silverback gorilla weighing in at about 400 pounds. Advantic and the zookeepers chose 1½-inch DURAGRID® HD-7000 grating from Strongwell, featuring glass-roving and glass-mat reinforcements and a synthetic surface veil for strength and corrosion resistance. The densely packed core of continuous glass rovings gives the bar strength and stiffness longitudinally, and the continuous glass mat provides strength in the transverse direction and helps prevent chipping, cracking and lineal fracturing, according to Strongwell.
Constructing the habitat with composite materials also had an added benefit for the zoo: It contributed to the welfare of the gorillas. For instance, installation time was about half the time it would take to install a comparable steel structure. “That’s less time the animals in the enclosure had to be removed to another space,” says Doudican. “That does a lot for animal stress and welfare.”
It also meant installers spent less time at the installation site than they would have building a stainless steel structure. This is helpful because their presence can sometimes distress the animals.
Advantic designed and fabricated the enclosure in its own shop using the stock components it received from Strongwell. “We professionally engineered, fabricated and pre-assembled the FRP and steel components of the structure and mechanical systems,” says Doudican. “Construction speed and efficiency greatly improve total installed cost, so we worked with the install team to kit the structure in modules like packaging an Ikea set. Then we loaded it in the truck and re-erected it at the zoo.”
The bridge is now in place and used daily by the gorillas to move from one part of their enclosure to the other. And, of course, they often stop at some point along the way to interact with viewers and gaze out at the zoo from their elevated position.