WSP served as the structural engineer for the 57-story building owned by Alexico Group and Hines. Silvian Marcus served as principal-in-charge and Hezi Mena was the project manager.

“I was delighted to learn of the ENR-NY award,” Mena said. “This is a welcome recognition of the creative thought process, time, and effort contributed by all staff involved in the project, especially when presented by such a prestigious publication.”

To select the winning projects, industry judges evaluated nominees in 18 categories based on the ability of the project team to overcome challenges, the project’s contribution to the industry, community, safety and construction, and design quality.

Nicknamed the “Jenga Building” for its cantilevered balconies that resemble the popular stacking game, Herzog and de Meuron’s architectural design created a collection of distinctive homes stacked up to a height of 825 feet.

“56 Leonard represents a very forward-thinking concept,” Mena said. “The architect’s innovative stack of homes suggests a new way of embarking upon the idea of a vertical neighborhood in which the end user can choose his or her own unique home, albeit in the sky. No longer is the penthouse the only level that breaks from the mold of the typical floor plan; an innovation of this kind presents an urban answer to the desire for traditional home ownership that is as singular as its occupant, while reducing the footprint of a conventional community of homes.”

“Taken as a whole, each of the techniques used in the structural design of the building support not only the aesthetics and architectural intent, but also provide a cohesive amalgamation of methodologies that have resulted in a notably successful project from a construction and budgeting point of view,” Marcus added.

One of the essential structural engineering issues with 56 Leonard was maintaining comfort levels during high winds.

“Considering that the motion perceived by building occupants is linked to the peak acceleration at the top occupied floor, it was necessary to provide adequate strength and stiffness,” Mena said. To achieve this, a liquid-tuned damper (LTD) with a footprint of 32 by 36 feet, and a total height of 10 feet, was placed at the top of the building.

One benefit of the LTD was the reduction of building mass, thus minimizing the amount of materials required for the structural system. In order to provide adequate lateral stiffness and minimize architectural impact, high-strength concrete of 12,000 psi was used at the lower levels.

“Our primary studies indicated that wall and column sizes in the lower third of the building would have required a 10 to 15 percent increase in order to match the structural performance achieved from the incorporation of a damper,” Marcus added.

An interesting yet expected structural engineering challenge was the number of “walking columns” needed to accommodate the varying apartment layouts throughout the building. This challenge was addressed by introducing one- or two-story walls that transfer the load from one column location above to a different column location below.

Rectangular Vierendeel trusses spanning two consecutive floors were designed to address the numerous cantilevers in the building, some of them reaching up to 25 feet. This structural strategy avoided any impact on the architectural intent.

“We believe the design of 56 Leonard will open new horizons in terms of architectural and structural design by tackling the idea of an ‘old fashioned’ mode of home ownership within the present vernacular of luxury urban living,” Mena said.

The ENR-NY award joins a growing list of honors bestowed upon 56 Leonard since its completion in 2016. Recent awards include the SEAoNY (Structural Engineers Association of New York) Excellence in Structural Engineering award and the Concrete Industry Board Award of Merit with Special Recognition-Design.

The features receiving accolades today are what originally attracted Mena to the project.

“Not only did the aesthetics of the project pique my attention, but its inherent structural peculiarities also drew my interest,” he said. “From the very beginning, it was clear that the distinctive nature of each of the homes required the design of one-of-a-kind floor plates for each story, in addition to numerous cantilevered protrusions. It was also evident the structural design would require ingenuity, creativity and dedication of specialized resources.”

The building, which was near full occupancy just seven months after it opened, has taken its place among the most iconic structures in the New York City skyline.

“This was an outstanding opportunity to devise an innovative and creative structural system for buildings, in which stacked floor plates fluctuate substantially from story to story,” Marcus said. “The fact that we were able to devise and implement a design methodology for ‘stacked’ residences of varied geometry will surely open new possibilities for buildings with similar aesthetics.”

“The project was uniquely challenging and, ultimately, uniquely satisfying,” Mena added. “The absence of typical floors in the building provided the opportunity for a continual, intense, and focused interaction between the design architect, the architect of record and the WSP team throughout the myriad of components required by the project. This has been an excellent experience for my team members and me.”

Will there ever be another building like 56 Leonard?

“As long as there is a human desire for progress and far-reaching innovation in design, and as long as visionaries are given the opportunity to create bold new monumental structures sculpted against the sky, buildings like 56 Leonard will challenge the resourcefulness of the engineer,” Mena said. “Although 56 Leonard will surely hold its particularly unique place in the history of iconic skyscraper design, it clearly ‘ups the ante’ for the next great structural challenge.”

Big Apple’s Best

56 Leonard was one of eight WSP projects recognized by ENR-NY.

ENR-NY presented an award of merit to another WSP residential/hospitality project: 432 Park Avenue, the 1,400-foot-tall, super slender residential tower in Manhattan. WSP served as structural engineer and mechanical engineer for the 96-story skyscraper, which is the tallest residential building in the Western hemisphere.

The Arthur Ashe Stadium retractable roof in Queens won the Best Project award in the sports/entertainment and excellence in safety categories. WSP served as structural engineer for the tennis-only stadium that hosts the U.S. Open every August.

The Kosciuszko Bridge phase 1 replacement project was the highway/bridges category winner. WSP was the owner’s engineer for phase 1, which opened to traffic in April; and will be the engineer of record for phase 2 of the project, which will begin construction in the fall.

Second Avenue Subway phase 1 was selected as the airport/transit Best Project. WSP was the consultant construction manager for the subway extension and station, which opened on Jan. 1.

The Jerome L Greene Science Center won the Best Project award in the higher education category. WSP provided structural engineering services for the building for Columbia University in West Harlem.

Lenfest Center for the Arts, also at Columbia University, was the winner of the cultural category. WSP was the structural engineer for the 55,000-square-foot building and its below-grade central energy plant.

860 Washington Street received the award of merit in the office category. WSP was the structural engineer for the 10-story, 113,000-square-foot building located adjacent to the High Line Park in Manhattan.

The ENR-NY Best Projects awards will be presented at a ceremony on Sept. 27, when the Project of the Year winner will be announced, selected from the Best Project-level winners.