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Toledo Zoo Elephant Exhibit in Ohio by JDI Group
July 11th, 2012 by Sanjay Gangal
Article source: Bentley Systems, Incorporated
The Portico Group (Seattle, Wash.), the lead architect on the Toledo (Ohio) Zoo Elephant Exhibit Renovation Project, contracted with the JDI Group of Holland, Ohio, to engineer the structural elements for an elephant shade structure. The man-made tree not only had to withstand wind forces and snow loading, but also the impact of a full-grown bull elephant ramming the trunk.
JDI’s structural engineers might have posed the question this way: If an angry 14,000-pound elephant rammed its head against a 40-foot artificial tree, how much force would the elephant exert on the structure? Of the 98 loading combinations analyzed during the design of shade structures for the Toledo Zoo elephant exhibit, that particular criteria was not found in the ASCE 7 Standard for Minimum Design Loads for Buildings and Other Structures.
“We analyzed many combinations of wind loads and wind in combination with snow loads, as well as seismic loading,” said Frederick Quinn, senior project manager at the JDI Group. “We had one load case—elephants—not covered in ASCE 7.We came up with scenarios for the behavior of the elephants by working with the zoo and their team of experts familiar with elephants.”
The man-made shade structures are part of a $14 million expansion of the zoo’s elephant display designed by the Portico Group. The structures were a practical alternative to live trees, which elephants quickly destroy by digging aroundthe base, eating the roots, and stripping the bark. The sturdy steel structures, constructed entirely of weathering steel, have tubular steel branches covered with netting to simulate leaves. The structures also support hoists suspended from the branches to dangle hay-stuffed barrels and other enrichment devices. Zookeepers can raise and lower the hoists and swap out various entertaining contraptions to keep the elephants occupied.
The shade structures are designed to withstand elephants leaning on them, rubbing against them, pushing on them with their forefeet, and head-butting them from a running start. The branches are high enough to be out of reach of the largest elephant, which may well be Louie, a seven-year-old youngster expected to be one of the biggest elephants on record at the zoo. When he is full grown, Louie should be able to reach nearly30 feet high when he stands on his hind legs.
Members Subject to Complex Forces
To perform the structural analysis, JDI imported Portico’s AutoCAD 3D geometry into RAM Elements. RAM Elements provides quick, reliable tools for specific structural tasks. It is the only structural engineering software system that offers finite element analysis plus stand-alone or integrated design tools all in one low-cost, easy-to-use package.
“It worked very efficiently,” Quinn noted. “We were able to bring all the node points and the total 3D configuration into RAM Elements, add the loading criteria and member sizes, and create the load combinations.” The analysis was complex because of the angled branches and numerous cantilevers and projections, and the structural elements were subject to flexure, compression, and torsion.
Load criteria for elements such as wind and snow were fairly straightforward. Elephant loads were deduced with the help of zoo management, which advised on such criteria as animal weight and the speed at which they can move. “We had to consider a potentially angry elephant,” Quinn said. “They are very intelligent animals, and the likelihood of ramming their heads into the structure is low, but we had to consider that possibility. How fast would an elephant be moving and what load would the elephant impart when it rammed it? That factored into the calculations.”
After adjusting the structural supports to withstand even an angry elephant, the final design was still in line with the aesthetically proportioned artificial shade tree envisioned by Portico. It was the size of the branch-like members that required some adjustment to support the simulated leaf fabric under snow and wind loads. “Aesthetics played a factor. The architects wanted it to look a certain way, so we played around with the member sizes quite a bit,” Quinn said. Even so, the framing ended up slightly larger than anticipated, but still within budget.
Quinn explained: “RAM Elements gave us a very economical design. For some of the members, we had to skinny down the dimensions to meet the architect’s requirements. Using the software, we could tweak the design very efficiently. We could increase other member sizes to redistribute the load, and take the load off certain elements to get the sizes down. RAM Elements made it very efficient and easy to do, and it was quick. You could run the analyses in a short period of time. If you had to do it by hand, it would have been a nearly impossible task.”
Two structures are now shading elephants in their expanded digs, completed in early 2010. Two more structures will shade the cow pen, which started construction in late 2010. A fifth, more petite structure will shade the rhino exhibit when it is renovated in Phase 3 of the improvement program, scheduled for completion in 2012.
The new elephant exhibit offers a state-of-the-art home for Louie, his mother Renee, and adult female Twiggy. The first phase has now been completed, and the three elephants are exploring its features and taking advantage of the enrichment opportunities that are provided throughout the facility—including the man-made shade.
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Category: Zoological Park
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