Fabricated metal structures support life-like environments

January 2012 - When visitors step into the Spirit Forest at The Chickasaw Cultural Center, Sulphur, Okla., they are transported instantly into a mature woodland humming with the sounds of wildlife. Here the rhythm of time cycles from daylight to sunset and starlight in just 20 minutes with the help of theatrical lighting and sensory effects. What most visitors don’t realize is the life-like flora and fauna is anchored by a skeleton of steel.

Designed by Hilferty and Associates, Athens, Ohio, and built by ThemeWorks Inc., High Springs, Fla., the Spirit Forest covers 2,500 sq. ft. and is the largest exhibit at the Cultural Center. ThemeWorks is a custom fabrication shop that combines a full range of services with the capabilities of artists, craftsmen and technicians to create engaging experiences at theme parks, zoos, museums and other attractions.

Steel support
“According to the center, Chickasaws traditionally believe that humans, animals, birds and smaller creatures of the forest are interconnected with each other and the rhythms and cycles of the forest,” says Ryan Kremser, senior project manager for ThemeWorks. “The idea of the exhibit was to communicate the strong spiritual connection that the Chickasaw people have traditionally felt with the natural world.”

The design concept for the exhibit included a cave that would take the place of a conventional entrance to the forest. “We wanted visitors to be struck with the size and scale of the forest environment as they emerged from the cave,” Kremser says. ThemeWorks’ task included designing a structure that could support several tons of artificial rock overhead.

“With years of experience in building similar exhibits, we start each project with a pretty good idea of what type of reinforcement will be necessary,” says Kremser. “We develop a proposal that details what we feel is a reasonable fabrication approach. Then we enlist the help of a structural engineer to analyze our plans, calculate loads and verify that the materials and design we want to use are up to code. We used 6-in. mild steel square tubing to construct the main support structure for the cave.” ThemeWorks can sometimes prefabricate framework at its shop in Florida. The framework for the cave was fabricated on-site because of its large size.

Realistic fabrication
The cave’s tube steel structure supports a hollow shell of artificial rock. ThemeWork’s skilled artists start to bring the rock shell to life by using hand tools to bend steel rebar into a wireframe grid that closely approximates the shape of finished rocks. As the work progresses, artists refer to a scale model of the completed cave to ensure the desired look is achieved.

Angle iron connects the rebar grid to the tube steel structure. Next, a mesh of metal lathe is attached to the rebar grid. Concrete is applied to the grid and sculpted to realistically mimic natural rock. The metal mesh supports the concrete while it cures and provides additional reinforcement. After the concrete cures, the “rocks” are painted and details like simulated moss are added for extra realism. “The walkways for the forest needed to be more substantial because rebar alone can’t carry the volume of traffic moving through the exhibit,” Kremser says. Steel tubing created the framework for the winding walkway. Corrugated steel decking, cut-to-size, was bolted to the framework before receiving a layer of concrete. The concrete was textured to look like compacted soil. Rock outcroppings were constructed with the same method used to build the cave. Fiberglass trees were bolted to metal risers for elevation and stability.

This recipe of steel tubing, rebar, metal mesh and concrete is used by ThemeWorks in a variety of applications from theme parks and zoos to places like the National Museum of the Marine Corps, near Quantico, Va. “Concrete can withstand a lot of compression but it has very little tensile strength,” says Kremser. “Instead of flexing, it breaks. By embedding steel in the concrete, we add tensile strength. The mixture gives us a tremendously strong material.” At the Marine Corps museum, a snow-covered battle scene covers steel and mesh instead of soil and rock.

For certain applications like SeaWorld’s Discovery Cove, Orlando, ThemeWorks had to exchange mild steel for stainless steel and plastic mesh for metal lath. “Stainless steel rod was used to form the grid foundation for rock formations near the dolphin lagoon,” says Kremser. “It is critical to use non-corroding materials in the presence of saltwater.”

For Kremser, the role of metal fabrication in creating realistic themed environments is essential. “Our team’s ability to work with metals is crucial to our company’s capacity to craft these environments because we rely on metals to do the heavy lifting,” he says. FFJ