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Bensonwood Builds Engineered Timber Structure for the Historic Bushnell Park Carousel

By Rick Reynolds

In Hartford, Connecticut’s famed Bushnell Park, under a giant oak tree, 48 hand-carved wooden horses, two lovers’ chariots and a Wurlitzer band organ, whirl around under a 24-sided pavilion, to the delight of children, newlyweds, and nostalgia lovers throughout the region. To add to this historic wooden carousel attraction—originally carved out of wood in Canton, Ohio, in 1914 by Russian immigrants and later moved to Bushnell Park—a new, attached, 12-sided building and extension, made with advanced, highly-fabricated Nordic Lam engineered timbers and steel, will serve as a foyer and function room in addition to housing ticket sales and concessions.

Bushnell_UPDATED TF SPECS_5.21.15_Page_1With the specs for the new building calling for engineered timbers, the on-site builder, DH Bolton LLC, reached out to Jean Marc DuBois of Nordic Lam, who in turn referred him to Bensonwood, the preferred Nordic Lam supplier for New England, to provide the material and the CNC milling. But once Bensonwood’s experience in building sustainable, wooden public buildings became known, the company was hired to fabricate, engineer, and install the FSC certified Black Spruce timber structure and multifaceted roof deck.

The challenges of the project, while many, were well-suited to Bensonwood’s Montage building methodology, where structures are first built virtually, then highly fabricated off site for rapid, low-impact installation on location. In particular, the ecological sensitivity of the site, with its nature park setting, overarching oak tree, and off-site drop-off point far from the structure, meant that neither the on-site cutting and shaping of the engineered timbers, nor the use of a crane to lift heavy prefabricated sections into place, would be feasible.”

Bushnell Park AerialTherefore, to minimize disruption to the site, segmented roof assemblies would need to be designed to lessen the load. With smaller, lighter roof components, a smaller Telehandler with man-basket could replace the heavy crane during assembly. But all this required great precision in engineering and fabrication to ensure all the interlocking pieces fit together flawlessly, as planned.

During on site assembly, the 32’ diameter, 12-sided building would have no rigidity to stabilize the 12 posts until the 12 rafters, roof system, and center locking ring, known as an oculus were all in place. Therefore, holding the heavy elements in position long enough to attach, would be tricky. Ordinarily, with the use of a crane, each large, pre-fabricated, pie-shaped roof section would be flown into place in one pick, to stabilize the structure section-by-section. But because of the great weight of the 4-inch thick Nordic Lam roof deck material and the limited lifting capacity of the Telehandler, calculations showed that multiple, graduated, interlocking, trapezoidal roof sections would need to be flown into place, one-by-one, and attached to the rafters, in order to make up each pie-shaped wedge. As is so often the case, necessity proved to be the mother of invention.”

After the timberframe and roof system are in place, the site builder will install the timber post infill framing within the plane of the structure, and to add to the thermal mass of the CLT material, a layer of rigid insulation will be attached. Finally, an asphalt roof with insulated underlayment will complete the building envelope.

With wood as the common theme throughout, the Bushnell Park Carousel project is a perfect marriage of Old World craft, New World sustainability, and the latest in 21st building science and materials, ensuring the century-old carousel will be delighting riders well into the 22nd century.