Developers of the new MGM Resorts International casino under construction in Springfield, Massachusetts, wanted to create a structural system that could be erected quickly with low structural loads to save material costs. To meet these needs, they specified a shallow steel frame supporting Girder-Slab D Beams and precast concrete hollowcore.
The $950-million facility will contain dining, retail, and entertainment services and is being developed on 10 acres of land heavily damaged by a tornado in June 2011. The plan includes a revived Main Street area with tree-lined streets and entertainment options, centered on the hotel and casino.
Hollowcore Benefits
“The hollowcore/girder-plank system offers a lighter superstructure than other options,” says Eric Nelson, vice president of Tishman Construction. “This resulted in lower column loads and smaller foundation systems. It also increased clear floor-to-floor dimensions, because the D beam is within the depth of the plank.”
It also sped up construction and produced a high-quality result, he notes. “It allowed materials to be cast in a controlled environment offsite, reducing congestion and easing logistics on-site, while provided good QA/QC as a PCI-certified precaster.” Fabcon Precast fabricated and erected the hollowcore plank.
The components consisted of 119,000 square feet of 8-inch-thick, 4-foot-wide planks along with 183 pieces (encompassing 21,000 square feet) of 8-inch-thick solid prestressed slabs used at the perimeter to handle side cantilevers, special shapes and circular areas.
Fabcon worked with Tishman Construction, the construction manager, on a design-assist basis and worked closely with Berlin Steel Construction Co., which manufactured the steel components and erected them and the precast concrete units. Prior to finalizing the design, the team considered several options, including steel frame, cast-in-place frame, and variety of alternative foundation systems.
The façade consists of a stick-built rainscreen system with a variety of finish materials, including glass-fiber reinforced concrete, fiberglass reinforced plastic, thin brick, fixed windows, stucco, and storefront systems. The façade is tied back to the girder-plank system at the perimeter wet-cast planks, which were used to achieve radiused profiles and address irregular geometries.
The building’s large footprint and prefabricated components allowed for a continuous erection schedule from west to east, with almost no downtime for the tower crane. “Weather was the greatest variable, particularly as it related to the grouting operation,” Nelson says. Erection of the precast concrete hollowcore plank proceeded two levels above the highest grouted level, with temporary enclosures and heat required in some cases.
The erection process took approximately 20 weeks in all, with the plank installation accounting for about eight week. An Ardex V1200 nonstructural floor-leveling material was applied to the precast concrete hollowcore plank after installation. The casino’s opening is planned for September 2018. |