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Engineered Solutions: Rising to the Challenge of Multi-Story Construction

Parul Dubey on April 6, 2020 - in Articles, Showcase

Sponsored by: New Millennium Building Systems

Long-Span Composite Floor Systems Meet the Various Demands of Low-Rise and Mid-Rise Structures

Multi-story construction projects often introduce multiple challenges. Whether it’s new construction or a renovation, choosing the right long-span composite floor system can solve a wide range of demands typical of mid- to high-rise multi-story projects. 

A long-span composite deck floor system supports the cantilevered floors of a 12-story luxury condominium project in New York City. The bustling area on the Lower East Side limited use of a portable crane to once a week and required on-time steel deck deliveries.


The Need for Space

The challenge was three-fold for a recent 12-story luxury condominium project in New York City: zoning height limitations, a neighboring building’s air rights and a narrow side street access point.

Located on the city’s Lower East Side, the condo building first needed access to the air rights above a neighboring pawn shop. Once that was secured, architects were able to realize their cantilevered design using a deep-ribbed composite deck floor system.

As the building increases in height, it increases in square footage thanks to cantilevered floors that extend a minimum of 15 feet over the adjacent building and cover a total of 50,000 square feet. The deep-ribbed composite floor supported the complex design in two ways: The system can span up to 22 feet unshored, easily accommodating the overhangs, while avoiding space-robbing steel beams, supporting columns, lateral bracing and the overall weight associated with those elements.

“With span-to-depth ratios equaling those of traditional cast-in-place concrete and hollow-core plank, a long-span composite system featuring deep-ribbed composite helps make steel frame solutions affordable and the design aspirations of architects possible,” says Marty Williams, design development manager for New Millennium Building Systems.

Getting to the jobsite was a peripheral problem. The narrow side street limited use of a portable crane to once a week and required carefully planned on-time steel deck deliveries.

The Need for Speed

Known as “the oldest race track in America,” Saratoga Race Course in Saratoga Springs, N.Y., needed a jolt of modernization. Track leadership decided in 2018 to add a new three-story, luxury trackside viewing and hospitality structure—and they wanted it ready for the 2019 season, leaving 10 months for construction.

The 1863 Club project broke ground Sept. 3, 2018; its target deadline was end of June 2019. Construction would need to be as swift as the horses that compete on the historic track. With the tight deadline in mind, the design team selected a lightweight, deep-ribbed long-span composite floor system that could be erected quickly.

Structural framing began in late November 2018. At the end of January 2019—just eight weeks later—work crews had the entire facility framed and ready for further construction.

How did the long-span composite system win? Deck panels were fastened to the beams using a quick two-bolt connection. A side-lap tool created a proprietary connection that led to rapid installation of the deck panels. The steel-and-concrete frame required no fireproofing. Its lightweight panels could be placed quickly. The deck’s long spans meant less time erecting support columns.

It was a photo finish: The project wrapped up just in time for the 2019 season.

The ability to quickly erect the lightweight deep-ribbed composite deck for Saratoga
Race Course’s new 1863 Club helped push the project over the finish line on time.


To avoid damaging this historic New York City factory being converted to condos, floor deck panels were delivered through the building’s windows, then carried into position without using heavy equipment that could damage wood columns and beams earmarked for preservation.

The Need for Integration

New York developer Metro-Loft had a vision to turn a former factory built in 1883 into luxury condos. Preserving the charm of the historic structure while updating it for modern living was a challenge.

The seven-story mid-rise was showing its age. The sagging wood floors required replacement, but the developer wanted the wood beams and columns to remain. A deep-ribbed long-span composite system was brought in to address both issues. It works with any beam or wall-bearing support system, including the aging yet usable original wood beams.

Workers replaced the wood floors with the deck in stages. Floor deck panels arrived via just-in-time deliveries to eliminate the need to brace adjacent walls. The deep-ribbed composite’s thin-slab attributes—up to 50 percent thinner than alternative floor systems—allowed the developer to achieve dramatic ceiling heights and incorporate radiant heating in the floors. 

The accompanying article was developed as an introduction to the category of long-span composite floor systems. A deeper analysis of these systems, in the form of a PDH article, is available online.

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