Designed by Populous and JRDV Urban International, the 17,255-seat arena for sporting events (and 18,500 seats for concerts) opened in November 2021, and features clubs, suites and lounges, ten bars and concessions, a state-of-the-art sound system, an NHL locker room and player campus with a cardio mezzanine level and shoot room, and an updated sports lighting, ice mapping/projection system and 12 all-player tracking cameras.

One of the primary design goals for the 745,000-square-foot arena was to create a venue meant for hockey, rather than a building that had been adapted for the sport as had the Islanders’ previous homes. Populous created hockey-specific sightlines for fans by designing the seating bowl to be closer to the ice than an arena that prioritizes basketball. This move produced an intimate experience that allows spectators to feel close to the action on the ice.

The arena architecture also supports current needs for immersive music concerts and other performances. A 400,000-pound rigging grid can support 300,000 pounds of equipment for an end-stage or center-stage setup (versus the 100,000 weight limit of most last-generation arenas). An industry first, the interior mezzanine catwalk above event-level premium spaces offers direct access to all utilities that serve the premium spaces from above, including Wi-Fi, gas, and electric. This prevents temporary closures or damage to ceilings, walls and other infrastructure, during possible repairs. There is also direct freight elevator access from the arena floor to the catwalk for continued ease of event operations.

A high level of structural engineering was required to execute the unique space. Its super- structure’s gravity system is a steel composite beam/column system with a steel-braced frame lateral system. Four long-span roof trusses, each weighing approximately 180 tons and running 35 feet deep at the middle, support the primary roof and create a 350-by-460-foot column-free space
for the seating bowl.

“The soils in the area are native Long Island sand with a very high bearing capacity of 10,000 psf,” explains Eric Lumpkin, project manager for Thornton Tomasetti, who performed the project’s structural engineering. “This meant the arena could be founded on shallow spread footings, which resulted in significant cost savings.”

As opposed to a traditional basement wall, the team chose a 20-foot-high concrete retaining wall to structure the below-grade spaces, which allowed the contractor to backfill the wall almost immediately.

The structural engineers also decided not to place the braces for the lateral load-resisting systems in the back of the seating bowl, as is typically done, in order to avoid having braces obstruct the concourses. Instead, they located the vertical braces in stair cores and around the perimeter of the building.

“Drag struts were utilized to collect load from the inboard portion of the arena and distribute it at the braced frames in the outboard stair cores and perimeter façade line,” explains Gary Storm, a senior principal at Thornton Tomasetti.

To help enable the 150 annual events scheduled for the arena, in addition to the hockey season, full-depth infill trusses span between the primary trusses to support the rigging grid for concerts and events, and a catwalk and platform system supports scoreboards, speakers, and sporting event lights. Lumpkin explains that the full-depth infill trusses are advantageous because the bottom chord also serves as a rigging beam for concerts.

The long-span roof was designed for a centerhung scoreboard with a weight of 120,000 pounds and a 30,000-pound offset hoist to lift the scoreboard. Fully nested into a 60-by-60-foot hole in the roof, this location supports show loads for concerts positioned under the scoreboard.

In addition to supporting the large rigging loads for speakers, video boards, lights, and other equipment, the arena is designed with a robust loading dock and marshaling yard.

“From an architectural standpoint, this meant increasing the number of loading docks and ensuring that the marshaling yard is large enough to allow for the delivery and movement of freight,” says Storm. “To accomplish this, the structural engineering team had to design large column-free spaces in the marshaling yard areas.” To create these spaces, a series of 10-foot-deep, 110-foot-long trusses were built over the marshaling yard to make sure that no columns would obstruct truck access to the arena.

Pointing out that the 60,000-square-foot marshaling yard is one of the largest in the industry, Jason Carmello, a senior principal and architect with Populous adds, “the yard is covered, enclosed, heated and provides ample power/data connections for 10-plus trailers, direct access to the loading dock and arena floor via ramp and creates one of the most accessible load-in/load-out sequences in the marketplace. The arena also has direct freight elevator access from the arena floor to the catwalk for continued ease of event load-in/ load-out.”

When COVID hit the U.S. in the spring of 2020, arena construction shut down for 50 days. When work resumed, New York State’s mandatory quarantine for all out-of-state visitors prevented the Kansas City-based Populous architects from visiting the site, with the exception of two individuals who were New York residents.

Thornton Tomasetti was able to rely on local colleagues for handling any necessary site work. “Luckily, we had a great group of staff from our New York office who were able to make site visits and be the eyes and ears for the design team back in Kansas City,” says Lumpkin.

“Each night, the design team would review site photographs taken during the day in order to give real-time feedback to site staff. Additionally, video calls over smart phones with site staff became a regular occurrence to review complex conditions in the field,” he says.

Quickly adjusting to these unique circumstances, the project team began using tools like HoloBuilder, which enabled the team to get a better look at slab which enabled the team to get a better look at slab reinforcing and structural steel with the software’s high-resolution, three-dimensional images that rotate, pan, and zoom.

In response to the new health and safety concerns, the design team also modified food service operations, MEP and filtration systems, patron circulation paths with added doors and entry-egress routes.

Another interesting byproduct of the travel ban was the architects’ ability to spend time that would have been lost to travel turning around Requests for Information and Submittals at a faster pace.

Fortunately, the majority of the structural materials—mainly steel, concrete, and rebar—were procured prior to the pandemic, so contractors AECOM Hunt and Barton Malow didn’t run into any major supply-chain issues.

Though the steel design and procurement was performed pre-COVID, the fact that Thornton Tomasetti had built its own Tekla model of the steel structure allowed the engineers to fully coordinate construction drawings, connection design, and fabrication models, which sped up the beginning of the project, and ultimately helped keep things on schedule despite the shutdown.

“Our Tekla model had all of the connections fully detailed and modeled with plates, bolts, weld sizes, holes, etc.,” says Storm. “The model was then passed along to the fabricator to generate shop drawings. The greatest advantage of this delivery method is the time savings achieved by eliminating the traditional pass-off to a third-party detailer and delegated connection designer.”

he design team also utilized Revit BIM360 to generate construction drawings. With the full design team in a shared cloud model, this eliminated the need to pass models back and forth between design firms. “This is advantageous from a coordination standpoint because engineers could see any changes in real-time in other engineering and architectural models,” adds Storm.

Digital modeling technology was also used to map out installation and track as-built progress for steel erection. With these geometric details precisely established, steel elements were positioned correctly the first time. The project site also worked to the team’s benefit as the contractors had ample room for steel laydown and staging.

The cutting-edge arena also features robust Wi-Fi networks with 5G speed communications technology embedded within the seating bowl through thousands of connections, wiring and antennas. Patrons can participate in interactive events via smartphones and take advantage of convenient grab-and-go options like Amazon’s Just-Walk-Out Stations. Targeting LEED certification, the arena incorporates renewable energy, reduced water and electricity consumption, and zero waste.

Alongside the new venue are plans for a 340,000-square-foot retail and dining complex, a 200-room hotel and a new Long Island Rail Road station which ran on a limited schedule last season and will be full-service later this year. The site is shaping up to offer something for everyone, especially dyed-in-the-wool Islanders fans who will celebrate the team’s 50th anniversary this coming season, finally in an arena worthy of their enthusiasm.

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The old LaGuardia, notorious for congestion, delays, and snafus throughout the passenger experience, could be mistaken for an overscaled Greyhound station. In 2014, then-Vice President Joseph Biden, a careerlong advocate of transportation infrastructure, famously assailed it as worthy of “some Third World country.” Yet the airport that travelers have complained about for years is finally becoming one to be proud of. HOK Architects, WSP, SkanskaWalsh, and LaGuardia Gateway Partners (LGP, a private entity selected by the Port Authority of New York and New Jersey to coordinate this long-overdue project and manage it until 2050), working within spatial constraints and staging demolition and construction amid continuous airline operations (complicated by pandemic conditions), have transformed LGA’s central Terminal B into a place that can elevate spirits as well as move bodies. Its physical form evokes greater New York; its technologies address critical functional problems; and its detailing provides what its predecessor lacked: a tangible sense of place.

The Port Authority’s goal for air passenger facilities, says project director Jessica Forse, is nothing less than “to make them world class and best in class.” The challenges to reach such a condition were obvious, with both landside spaces and airside operations stretched past their capacity. “Anybody that knows LaGuardia,” says Paul Auguste, HOK’s director of aviation and transportation, “knows you get in the plane and you’re sitting on the taxi lines for minutes, hours, whatever it is, trying to queue up to get to the runway.” The airport needed to replace its crescent of four terminal piers and expand airfield space for aircraft and service vehicles. Yet LGA, sandwiched between Grand Central Parkway and Long Island Sound, lacks the lateral greenfield area that other airports might expand into. Reconfiguring it was not unlike building a ship inside a bottle.

The Port Authority’s initial plan, Auguste says, called for a linear headhouse with a series of piers,
“very similar to what was there,” requiring a complex construction process that “would have made the existing operations impossible.” Instead, HOK and partners
“looked at how we could phase this to save time and money,” Auguste says;” because the crescent-shaped headhouse was there, and you need to maintain operations for departures and arrivals, we changed our design to fit the site.” HOK and partners moved the headhouse as close as possible to Grand Central Parkway, some 600 feet south; removed a 3,000-space parking garage; and created two separate concourses in the form of islands connected to the headhouse by pedestrian bridges stretching over taxiways. This arrangement recaptured about 40 acres of airside land and gained two miles of usable taxiway, allowing aircraft two paths to each of the 35 gates (instead of pulling in and backing out) and easing services such as fueling and baggage handling. The skybridges also give pedestrians a striking view of planes passing underneath as well as panoramic views of the Manhattan skyline. Terminal B is now a microcosm of New York, a city of islands linked by bridges.

Derek Thielmann, LGP’s project director for design and construction, says the revised plan meant “we could build a new headhouse without impacting traffic to the existing terminal, and then we had other real estate to the east,” where they placed a new central heating and refrigeration plant, additional apron, and a concourse, then figured out how to connect the components. “We came up with a phasing plan that basically shrunk the Port’s plan from 16 phases down to five… We were maintaining existing airport operations while we were able to construct all-new infrastructure, and our phasing allowed us to actually frontload the construction, so in the first three and a half years, we were essentially delivering about 75 percent of the project.” The island concourses allowed some construction to take place above the old terminal before demolition, saving time and costs; only one gate had to be closed at a time. The new 850,000-square-foot terminal uses 40,000 tons of steel, including nearly 10,000 pieces in the Arrivals and Departures Hall, weighing 12,000 tons (heavier than the steel in the Eiffel Tower).

“From the airlines’ perspective,” Auguste comments, “it was brilliant… one day overnight, they went from the old facility to the new facility.” Aircraft now “have multiple avenues to taxi around all the operations of Terminal B and get to the runways quicker, so we have greatly reduced the congestion; it greatly reduced the time it takes to get to the runway, so it’s going to be a win-win for airport operations, airlines, and passengers. You’ll never have those crazy 20-plane piers trying to get to the runways any more.” Interior dimensions are also generous, Auguste adds: “The old concourses were about 60 feet, 65 feet wide, with eight-foot ceilings. The new concourse has 55-to 60-foot ceilings and is 120 feet wide.” With 1.3 million square feet of new terminal space, Terminal B gives passengers on five airlines (American, United, Air Canada, Southwest, and JetBlue) a capacious atmosphere, defined by verticality (the four levels include mezzanines) and generous light wells on both landside and airside. The building’s form also “allows us to maximize the heat that’s rising up and heating all the levels, not just dissipating underneath the ceilings and in other space. So we have an atrium design that really created this efficient mechanical model.” Though airports commonly locate long walkways underground, the LGP team ruled out tunneling to the island concourses after considering site conditions. “It had a number of challenges,” Thielmann says, “just given the water table we have here at LaGuardia,” as well as maintenance. “And so we elected to go above and go high,” not only saving construction time but giving LGA an immediate pair of icons. The bridges, composed of structural steel trusses with glass curtain walls, are more than corridors; with furniture, discreet video signage, and ample headroom, they are high points in the passenger experience. “We’ve managed to incorporate some of our food and beverage offerings into both bridges,” Thielmann continues, “so people can actually sit down, have lunch, and have planes taxi underneath their feet.”

Local aerospace enthusiasts may recall Eero Saarinen’s TWA Flight Center at JFK (1962) as an aesthetic triumph with dramatic concrete forms that quickly became impractical: its gates were too small to accommodate the next decade’s jumbo jets. Here, the design is future-proofed. Skybridges A and B, spanning 500 and 450 feet long, respectively, are elevated about 60 feet above the elevated about 60 feet above the tarmac, high enough to allow not only the Airplane Design Group III aircraft that use the terminal (with tail heights 30-45 feet high, as defined by the Federal Aviation Administration) but Group IV (45-60 feet) as well. “If for some reason a Group IV aircraft got lost and was headed that direction,” Auguste says, “without any fuel in it, without any passengers in it, full air in all the tires, so it was high as it could be, it still clears underneath our bridge.”

HOK structural engineer Francesca Meola points out that a proprietary parametric modeling tool, now called HOK Stream, allowed crucial calculations within a tight timetable. “We were able to quickly generate models to understand the behavior,” she says, “and understand if the solution was cost-effective and if it was performing, not only from a structural standpoint for strength and serviceability criteria, but also for performance for vibrations, because with pedestrian bridges in particular, you have a mass of pedestrians walking at the same time.”

The vertical trusses, with a depth varying from 20 to 40 feet above an eight-foot base concealing ductwork, are connected with moment-frame beams in the vertical plane, and with horizontal bracings on the roof and in the plane of the bridge deck, for lateral stability. The chords, Meola continues, are flat built-up I sections; the diagonals combine rolled sections and built-up sections, with grade 65 steel for the longer, shallower Bridge A and grade 50 for the shorter, deeper Bridge B. Braced frames for the longitudinal direction are necessary only on the concourse side, near escalators and elevators.
“During construction,” she says, “we were actually able to time the final base connections of the front row of columns to eliminate any permanent tension in the foundations that would have resulted from the north bridge towers acting as fixed elements. The capacity of the piles in tension is like a third of the one in compression, so this strategy allowed for substantial savings in not just the superstructure but even more in the foundation system.”

The concourse roofs, Meola says, are flat on one side, “but then it folds to follow the line of sight, so we were able to follow the shape with these trusses,” four feet six inches deep and bent. In addition, “we minimize the impact of the lateral system. Everybody complains about brace frames; nobody wants columns, and nobody wants brace frames; so we were able to locate those right where we have stairs, so they will not impact on the flow of people walking, and they would not be in the middle of the structure.”

The bridges expose the trusses, clad in glass-fiber-reinforced concrete and gypsum (GFRC and GFRG), as expressions of the structure, implicitly conveying the scale, strength, and stability of the steel as well as maximizing views for departing or arriving passengers. Where the old LGA’s generic, dingy spaces compelled hasty movements, much as Penn Station brings out every commuter’s inner scurrying rodent, the new LGA’s high ceilings and graceful members impart a welcome sense of calm. The Arrivals and Departures Hall is a four-story structure
with three separate roadways for different functions, Auguste notes: ground level for buses and other high-occupancy vehicles, the second for arrivals (including conventional taxis and private-car pickup), and the third for departures. Planned before the rise of Uber, Lyft, and similar ride-hailing services, the facility relegates for-hire vehicles to the new parking garage, geofenced, Thielmann says, to prevent motorcar tsunamis in the pickup area. From entrances to gates, Terminal B is designed for intuitive movement and confusion-free wayfinding.

Rethinking interior pedestrian traffic required a complete redesign of spaces built before Transportation Security Administration (TSA) screening became such a large and stressful component of a traveler’s experience. In the old LGA, amenities appeared in pre-security spaces, Forse recalls; one sometimes ate before passing through security, a sequence hardly imaginable in the TSA era. In contrast, the new terminal is “designed for the way air travel occurs today,” reproportioning pre-and post-security spaces to assign nearly all shops, restaurants, and services to the latter.

TSA is centralized and located off the main Departures entrance past 75 check-in counters and 105 self-service kiosks, with state-of-the-art features to smooth the process: dynamic video signage in the queuing area informing passengers of expected wait times, automated baggage screening and tub-handling technology, and 16 screening lanes. Post-TSA recomposure spaces,
a feature that few airports give adequate attention, are generous, with ample seating and tables, easily cleaned carpeting—so that, in Auguste’s words, “you don’t want to go through there like I do and feel like I need to take a shower afterwards”—and a large curtain wall. “All the time the passenger is going through,” he says, “you know exactly where you go when you’re looking through the window at the apron right out front; you have a sense of direction all the time.”

Forse notes that the Port Authority’s master plan calls for a central hall connecting Terminal B to Terminal C (privately owned by Delta Airlines and under separate renovation), with AirTrain access, another long-standing oversight.

New Yorkers and visitors have put up with disruptive site work since 2016, but we put up with the old LGA for much longer. Only time will reveal important metrics such as airline on-time performance, energy consumption, or improvements in accessibility once the AirTrain component is sorted out. Yet it is an excellent time to get used to a novel sensation: having an airport that makes us stop rolling our eyes in exasperation and start lifting them in admiration.

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The most dramatic addition is the undulating 92-foot-high glass canopy that covers the train hall. This “skylight” comprises steel diagrid members fabricated by Seele, arranged in four bulbous east– west segments supported by massive trusses from the original building: structural members that also enhance the building’s muscular aesthetics, strength- ened by new color-matched beams. An additional north-south glass vault covers a corridor west of the main hall at the center of the building between Eighth and Ninth Avenues, linking its 31st Street and 33rd Street entrances. New steel canopies at those entries are designed “to complement McKim Mead & White’s Beaux-Arts architecture,” says SOM design architect Andrew Lee, and to “reflect the language that we see in the skylight,” introducing visitors to the hall’s balanced aesthetic upon entry.

The junctures between the glass canopy and the original building’s masonry are covered by metal paneling to create seamless connections around the hall; additional metalwork includes column-cover wraps, guardrails, handrails, handrail shoes, and functional grilles that support lighting and conceal paneling.
ductwork. The uniform appearance is deceptive, because “every one of these panels and every one of these grilles is a different size,” notes Permasteelisa
director of business development William Bueso. “Every item we’re doing is a custom one-off piece made specifically for this job … the only stock things we’ve ordered are the screws, nuts, bolts, and handrail shoes.”

For Lee and his colleagues at SOM, the mission involved “celebrating the heritage of this building,” which is both an echo of the civic dignity of the original Penn Station and a no-nonsense functional facility. “It wasn’t an exactly thoroughly finished building; the inside was more of an industrial building,” Lee says. “We tried to reveal some of the existing structure by highlighting some of the articulation and the ironwork of the past rather than doing new pplications of metal… taking that language and using ornamental metals to recreate some of it in areas where it wasn’t as highly finished.”

In a transit facility, Lee adds, “finishes at the human scale have to be extremely durable and stand the test of time.” The design team selected a material palette that is “not evoking some of the connotations that stainless steel typically has; it’s very institutional… there’s a way to finish it to a higher quality that maybe leaves out some of those connotations.” With ample LED signage and video displays, at any rate, the hall hardly needs the sparkle of reflective surfaces. Lee described the paneling and grillwork as “generally very quiet…. To really tread lightly in that train hall space, so that you let the skylight and the existing structure breathe.” At staircases between the concourse and platforms, he noted, glass guardrails “minimize the kind of visual clutter that would be in a very busy space to begin with,” optimizing sightlines to the platform level and aiding navigation—a distinct improvement over the abattoir claustrophobia that has provoked complaints over Penn Station’s traffic flow for decades. A grand staircase, seven elevators, and 11 escalators expand vertical circulation options.

Like any transportation center, Moynihan is a massive job; it is complicated by its combination of existing and new structures, marrying 21st-century
steel to 1912-vintage masonry. Retrofits pose challenges that new construction does not, particularly where onsite investigations discover details that
were not apparent at the design stage. “You can’t foresee some things that are on a 67-year-old truss,” observes foreman Will Jones. “They didn’t know it
until you got inside.” Pointing during a site tour to various anomalies that the project’s design documentation did not predict—cross-bracing in old trusses; lighting wired through a truss; brackets that had to be replaced when onsite calculations revealed that a beam with attachments could not support a grille; beams that shifted when they were loaded with glass and wires were tensioned—Jones observes that a degree of improvisation goes with the territory. “One of the challenges with an existing building,” he continues, “is building things ahead of time to meet the schedule, and not quite understanding, because you didn’t have a chance to really dive into a lot of the details, how that’s going to fit on the job site. On a new building it’s a little easier to do that; on an existing building it’s harder, because you open this up and boom! I uncover this site condition.”

At Moynihan, energy-conservation features include radiant flooring on the concourse level, which will heat and cool the entire building; this required in- stalling a piping system before pouring concrete, the type of up-front investment that saves resources by heating air efficiently from beneath occupied spaces and lowering the overall volume of ductwork through- out the hall. “We underestimated the existing-building component of the project,” Bueso notes, speculating that general project cost overruns reach the 20–30 percent range—distinctly lower than found on the city’s only comparable recent transit hubs, the World Trade Center PATH Oculus and Fulton Center.

Considering its spaciousness (255,000 square feet), its expanded connectivity (creating direct station access from Ninth Avenue for the first time, along with the midblock entrances on the two cross- streets), and the relief it offers to two of the three rail systems squeezed into Penn Station, Moynihan Train Hall is a critical upgrade on all fronts. The anticipated scale of passenger traffic ensures that the project is not so much a matter of “if you build it, they will come” as “since so many of them are coming, can we build a facility they can bear, possibly even en- joy?” The hall’s balanced elements give the region’s travelers a space that respects both its own history and their dignity.

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Any supertall skyscraper is, among other things, an embodiment of optimism. Who, after the past two years, has had much room for optimism? Employment rates and commercial rental markets have taken a hit. The ad hoc shift to work-from-home has reduced demand for office space either momentarily or permanently, as workers and organizations reassess which activities do and don’t need physical presence. There will inevitably be observers who believe a major new Class
A commercial building is the last thing the city needs, and not all of them are NIMBYs.

The team that gave the city One Vanderbilt, however, is looking beyond the present and near future. The new building, they contend, is more than just a paragon of sustainability, with $17 million worth of investment in features that give it an exceptionally low carbon footprint for its scale. It emerges from a pathbreaking public-private partnership involving the City of New York and the Metropolitan Transportation Authority (MTA). And it is essential to the reinvention of East Midtown, the 78-block area that City Council rezoned in 2017 with an eye toward relieving congestion, encouraging transit use, and upgrading aging building stock. Occupying the block bordered by 42nd and 43rd Streets and Madison Avenue, and replacing the lowest block of Vanderbilt Avenue with car-free space adjacent to Grand Central Terminal, the building may be the nation’s most conspicuous example of transit-oriented development.

The neighborhood’s need for up-to-date and uncrowded space is clear. One Vanderbilt not only contributes 1.7 million square feet of commercial space but integrates on multiple levels with the terminal. “The One Vanderbilt project included $220 million in public transit improvements,” Moss says; these include a new subway entrance, a 4,000-square-foot transit hall inside the tower, and ADA elevator access to the subways and trains. “The improvements will allow for one more train to run on the congested 4/5/6 subway line per hour, which will help relieve congestion during peak hours.”

One of the building’s distinctive qualities is its deference to other elements of its neighbor- hood. “A major challenge was to design a super-tall structure
that would not overshadow, but complement, its neighbor Grand Central Terminal,” Severud’s Daniel Surrett says. By convert- ing a block of Vanderbilt Avenue to a 14,000-square-foot plaza, redistributing space from motor vehicles to pedestrians and trees, One Vanderbilt increases safety while giving people more room to move and breathe. Its facade rises two stories west to east along its south face to expand views of Grand Central beneath its signature oblique cantilever and orange soffit. Jules-Félix Coutan’s sculpture Glory of Commerce (1914), showing Mercury, Minerva, and Hercules surrounding Grand Central’s exterior clock, is no longer obstructed from the west by a Modell’s Sporting Goods.

With tapering trapezoids, One Vanderbilt loosely resembles an update of the diagrams that Hugh Ferriss drew to illustrate the principles of New York’s 1916 zoning law, the regulation that established setbacks admitting light to the streets throughout Manhattan’s business districts. Ferriss’s sharp pyramidal forms were a transitional condition, an abstraction to which orthogonal wedding-cake setbacks aspired. One Vanderbilt dares to literalize such geometries, suggesting a tall ziggurat or, in the uppermost segments, a craggy iceberg. These nonorthogonal volumes and oblique load patterns called for careful handling by the structural engineers, whose close involvement with the designers from early stages resulted in time- saving, problem-solving measures on multiple fronts.

“Three faces of the building step outward at the fourth floor, including the southern face,” notes Moss. “Cantilevered trusses are provided to pick up columns at the fifth floor, while the outer regions of the fourth floor are hung from the top chord of the cantilever. As you move toward the east of the building’s southern face, the transfer trusses become shallower, allowing the structure to fit within the angled facade profile. The uplift forces in the back spans of the cantilever trusses are resolved by connections to the core shear walls.”

The prominent notch in the east facade is achieved by sup- porting perimeter columns on cantilevered steel trusses and plate girders that are tied back to a robust concrete core. Truss members are custom-fabricated out of ASTM A572 Grade 50 plates up to 8 inches thick and welded together, since the load demands exceed the capacity of standard rolled shapes. The plate girders are fabricated out of the same material and sizes. Connections
at truss panel point nodes were built up out of laminated plates seam-welded together. In some instances, forces at nodes were so great that isotropic solid steel forgings with the greatest dimension exceeding 8 feet were necessary to transfer them.

Many of Midtown’s older commercial buildings have 20×20-foot column grids, considered obsolete by tenants who prefer open floor plans. In One Vanderbilt, Surrett says, “there are no perfectly vertical steel columns in the building below the highest occupied floor, and an effort was made to keep the corners of the structure column-free.” End connections of beams were designed to resist the lateral ‘kick’ forces induced by the slopes of the columns. The outrigger trusses on dedicated mechanical floors tie the perimeter columns to the core to engage them in the lateral sys- tem and effectively create a wider base to resist lateral shears and overturning moments. Outrigger trusses were skewed slightly along the four sides to hit shear wall intersections and provide the most direct load path possible. Column-free beam spans approach a maximum of 70 feet. Vibration of the floor systems was considered extensively, and in many instances controlled the de- sign of floor beams over strength or deflection.

Severud’s Edward M. DePaola points out several benefits of the non-orthogonal design. “The slope of the façade is always on the main axes of the building (either north-south or east-west), so floor spans remain consistent on every floor. The taper results in less width of building surface (sail area) with height.” Because wind pressures are larger on higher floors, these reduced floor areas result in less wind-shear force on the building. Midtown’s density can contribute to complex wind patterns as prevailing southwest winds move around other build- ings; the design/construction team conducted wind-tunnel testing, using “a ‘proximity model’ that takes into account the sur- rounding neighborhood, the low and tall buildings, the avenues and the streets, so everything that may affect wind loads on the building [is] taken into account…. Together with the architect, we were able to ‘notch’ the corners of the tower. That shape helps break up the eddy currents that form downwind as the air mass travels past the building. The spire used the same concept,” says DePaola.

Vibration from below posed a potential challenge for a building married to a major transit node, but “the mass of the cast-in-place concrete foundation walls and concrete core provide vibration and sound mitigation such that isolation pads in the foundations are not required,” Surrett notes. DePaola points out that the only line adjacent to the property is the 42nd Street Shuttle between Grand Central and Times Square; vibration analysis indicated that the low-speed S trains, which stop west of Madison Avenue, have no impact on One Vanderbilt. Metro North tracks are also far enough away to have no effect. Another stabilizing element is a 520-ton tuned mass damper at the top of the building, which moves out of phase with building deflections to reduce wind-induced accelerations and increase comfort for occupants. “It is tuned to match, as closely as possible, the building frequency and period,” DePaola says; its tuning makes it effective during one-year and ten-year storms. The damper’s effect is sufficient, Surrett observes, that “space at the top of the building, with amazing views, may support uses as sensitive as fine dining.”

KPF architect Andrew Cleary, speaking at an American Institute of Steel Construction panel in September 2019 shortly after One Vanderbilt topped out, noted that after breaking ground in October 2016, the project progressed ahead of schedule and under budget. Real-time parametric analysis accounted for much of this performance: using Rhino, Revit, Grasshopper, the model- ing program Tekla, and Thornton Tomasetti’s proprietary collaborative BIM system Konstru, the design process determined pre- cise details such as exact beam lengths, bolts, and welds earlier than on conventional design- bid-build projects. Modeling allowed early coordination of all subcontractors and prevented onsite clashes. “If we catch one hitch that typically would happen during construction, we’ve paid for these guys to come in early,” Cleary noted; “if we catch two, we’re ahead of the game.”

One Vanderbilt is a structural hybrid with a steel frame and concrete shear walls. In a departure from routine practice, the light steel frame was erected first along with the main framing; the concrete core followed, about 10 floors below the steel, with the pouring of the floors. Moss describes “a lateral system that allowed for steel construction to be up to 12 floors ahead of core shear-wall construction. The steel members were designed to fit within the shear walls. We added shear studs to the steel members, allowing the shear walls to engage the embedded steel structure. This construction sequence required additional steel tonnage, but it allowed for a faster construction cycle.” DePaola credits firm founder Fred N. Severud with the steel-first erection sequence—“the Severud system, I like to call it,” keeping different trades from holding up each other’s progress.

Planning the steel and concrete operations required detailed advance measures. “Mechanical couplers for rebar splices were utilized in lieu of lap splices extensively to reduce congestion between the steel frame and the rebar and minimize” the thick- nesses of the shear walls,” Surrett says. “Strategically placed copes and holes were provided in steel beams and connection plates to allow the continuity of vertical and horizontal reinforcement. Add to that the accommodation of shear wall penetrations for MEP distribution in and out of the core, and you have quite the puzzle to solve. Design concrete compressive strengths were up to 14,000 psi, and lab test results consistently exceeded expectations. One notable accomplishment was pumping over 4,000 cubic yards of concrete into the building’s mat foundation in a continuous pour in sub-freezing temperatures.” The 27-hour operation in February 2017 was one of the largest single pours in the city’s history.

The process, which DePaola likens to “a ballet,” has yielded a building with a well-integrated aesthetic presence as well. The oblique-angle motif of the cantilevered south facade is matched by ventilated spandrel panels at each floor, including 34,845 glazed white terra cotta tiles molded with an identical angled pattern rising left to right; upper unoccupied segments near the spire pick up the same motif, complicating the building’s verticality with a consistent visual rhythm. The facade includes 8,743 curtain-wall panels in 1,060 different configurations, composing 753,500 square feet of curtain wall.

Developer SL Green is a believer, not just an investor: the firm is moving its own headquarters into the build- ing. They and other tenants will enjoy a 30,000-square-foot amenity floor with a 145-person auditorium, lounge, boardroom, and outdoor terrace, among other perks. On the 59th floor, an observation deck designed by Snøhetta, The Summit at One Vanderbilt, includes two glass ledges above Madison Avenue—a view to rival KPF’s other recent vertiginous project, the Edge at 30 Hudson Yards.

The supertall category attracts reflexive skepticism in some quarters, especially in the wake of Hudson Yards, where ten-digit public expenditures aided luxury- level private interests without arguably creating corresponding civic benefits. In the case of One Vanderbilt, however, skeptics will need to consider nuances and recognize the details of the public-private negotiations. Approval did not come easily here. In return, the city gets some badly needed transit upgrades, ample property taxes, the addition of a pivotal location to the local reservoir of vehicle-free space, and a model for the continued greening of future skyscrapers—plus a resounding rebuttal to those who believe New York’s glory days are behind us, that the future has no room for the exhilaration of thousand-foot views.

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The parametric steel-and-glass structure atop the neo-Georgian shell’s brick, limestone, and terra-cotta tracery is a stylistic surprise but, to some observers, incongruously harmonious. Todd Poisson, partner at BKSK Architects, recalled the extensive historical research that led to the design after owners Reading International, a theater/real estate firm, invited architects to reimagine Tammany Hall. Recalling the competition brief, Poisson says, “They wanted to move away from the name Tammany, which referenced the Lenape chief Tamanend,” a clan leader of indigenous peoples from the northeastern woodlands. But he and his colleagues took a contrary approach— “Why don’t we re-embrace the name Tammany in a way that they wouldn’t expect and look at Tammany’s history?”—and won.

The architects consulted with the Lenape Center on questions of cultural authenticity and developed a parti that would replace the building’s “pretty tepid slate hip roof” with a dome evoking not only a turtle shell rising from the sea (an image from the Lenape narrative of the North American continent’s creation, and the icon of Tamenend’s clan) but also the domes that were common in Georgian and neo-Georgian design. The Tammany Society’s previous headquarters on 14th Street was domed, Poisson noted, and in England and the U.S., “there were some references we found that got their domes 100 years after they were built…. Using that as inspiration, and other classical domes throughout the history of architecture, we modeled our dome to honor Tamanend with a little organic source material,” commingling Lenape and English heritage. Only this dome would be executed in steel and glass.

A structure driven by such symbolism required exceptional precision in design and construction. Stefan Zimmerman, senior branch manager at the Würzburg, Germany, branch of Josef Gartner GmbH, a member of the Permasteelisa Group, pointed out that the roof is a true free-form design, not a pure dome based on fixed circular radii or ellipses. “This means that every single member is different in shaping and different in geometry, different in angles,” Zimmerman explains. “So the individual surfaces of the canopy have been broken down into triangles.” Such a geometry, he adds, “creates angles between the tubes, it creates angles between the nodes, it creates torsional twists for the tubes, which all need to be accommodated in the node points.” The tubes are relatively simple with a 90-degree end connection, and the complex node points are CNC-machined. Wrapping the dome frame above an arched pediment at the 17th Street entrance created particular geometric challenges. None of the glass is curved; the precise design and machining generates the appearance of curvature with large numbers of small straight steel members, joined at approximately 1,000 node points, supporting triangular double-pane insulated glazing units (IGUs), each combining SGG Cool-Lite Xtreme and Parsol Grey glass panels by Eckelt. “The upper dome glass on the fifth and sixth floors has a darker tint to address glare and thermal comfort, while the lower hipped roof zone glass is slightly clearer, as it is a clerestory glazing for the fourth floor, and is partially shaded by the terra-cotta sunshades,” says Poisson.

Because of fire-protection regulations, Zimmerman says, “the wall thicknesses of the steel are higher than they would have needed to be for structure and for deflection requirements.” The dome is fully self-supporting, and a new concrete liner wall at the perimeter takes the steel structure’s entire load, with no columns touching the steel structure and no internal loading onto the floor plates. The unique shapes of all components called for exceptional logistical control on the job site, along with caution in packing and handling.

Prefabrication of tubes and nodes at Gartner’s German factory included steel lettering to guide assembly. A system of offsite storage and regular shipments to “feed the site with the demand for the next two, three days” overcame storage limitations at the tight downtown Manhattan site.

Rayhaan Nagrath, project manager at Gartner’s New York office, points out that the dome includes areas with two roof types, designated RT1 for the dome and “bull nose” (a protruding segment atop the western facade toward Union Square) and RT2 for the lower perimeter glass. “The bull nose breaks up the two systems,” Nagrath notes, “and the frames for the RT1 and the RT2 are constructed differently.” The RT1 frames include a node system, connecting node to node with horizontal purlins, with a hole in each node as a modular design feature allowing optional mountings, while RT2 frames are composed of purlins without nodes. Purlins include bolts for sprinkler attachment. Support brackets separated from the steel allow the entire structure to move under wind loads, preventing bending and glass breakage. Steel fins placed strategically 11⁄2 inches above the glass articulate the form to help create a dynamic image from the street, and act as a net to disperse snow loads and prevent unexpected avalanches. A hip-roof segment below the dome uses terra-cotta sunshade panels in multiple shades of gray, helping control solar gain and providing visual variety.

“We really wanted to be harmonious with the landmark base building,” Poisson comments. The fins “serve as further articulation of the shell, to make it more harmonious with the scale of both the stonework of the base and the tracery of the window mullions and muntins, especially at the second floor. There’s a balcony with doors with beautiful tracery muntins above it, which we replaced in kind. So we were inspired by the details of the existing building for the scale and detailing of the dome. We wanted to have enough articulation so it did not appear alien.”

After factory pre-assembly of the RT2 frames, installation of both the dome and the terra-cotta panels proceeded from the top down. The total assembly uses approximately 50 frames and 300 purlins to support its 800 glazing units; “pretty much every aspect of this job is unique,” Nagrath says. With its custom components and a high degree of structural interdependence, plus limited space for shoring points during construction because scissor lifts needed room to move, tolerances throughout the frames had to be extraordinarily tight, meticulously checked, and adjusted at each step. The pace of construction, he reported, was “about a frame a day, plus some time for all the intermediate purlins,” plus the glazing, averaging 13 glass units per seven-hour workday.

This painstaking process has yielded a building that has begun garnering honors before even opening, winning an AIA-New York QUAD Design Award in 2017. Zimmerman notes that Tammany may be a difficult precedent to replicate elsewhere. “This is more like a piece of art than a real building envelope,” he says, and he knows of no comparable domes in New York. But the sentiment behind it is one that could inspire architecture the world over; it has restored one of New York’s long-neglected treasures to the public eye.

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Designed by Dutch architecture firm Mecanoo in collaboration with Beyer Blinder Belle Architects & Planners, the project aimed to add 35 percent more public space to the building, which receives approximately 1.7 million visits every year. The MML was originally located within a former 1914 department store, which it occupied in 1970, and its interior retained many of the spatial constraints and systems of the retail space, including varying ceiling heights, an escalator, and poor ventilation.

One initial focus for Mecanoo founding partner Francine Houben was an opportunity to design a contemporary complement to NYPL’s Stephen A. Schwarzman Building (SASB), located across Fifth Avenue from SNFL. (Mecanoo and Beyer Blinder Belle have collaborated on programming and design across both locations.) That building, designed by Carrère & Hastings and opened in 1911, shares a Beaux-Arts style with neighbors on Fifth Avenue, and the architects used that influence along with neighboring copper clad mansard roofs, as a jumping off point for the SNFL’s signature rooftop design. The other major goal of the renovation was to make use of an unusual floor plan, which had one long leg between 39th and 40th streets where the department store’s loading dock had been.

“We came up with the idea of the Long Room, named after the library of Trinity College in Dublin,” says Houbin. This solution allowed the architects to use the oblong floor plate to create completely browsable and accessible stacks for the library’s 400,000 books and other materials. To house that much media, the team that included Silman as structural engineer devised a plan to create five floors where there had previously been three. “We really wanted to use the columns,” comments Houben, referring to the building’s structural steel frame. The solution was to cut a triple-height void into the floor slabs, 31 feet wide and rising 85 feet from the second story to an abstract ceiling artwork by Hayal Pozanti to echo the famous muraled ceiling of SASB. Now, this linear atrium separates three floors of flexible, daylit reading areas on one side and five levels of book stacks on the other, an efficient solution to balancing the need for a browsable collection and the library’s desire for more public reading room space. Through SNFL’s 40th Street windows, passers-by can see the northern end of the book stacks, visible as a continuous vertical wall of book spines welcoming them to browse.

This alteration required the demolition of the third and fourth floor slabs at the east side of the building, which Silman replaced with four new framing levels for the stacks. The floor slabs adjacent to the Long Room were removed at consecutive levels to create a multi-level open space. Bridges connect the main floor levels to the tiered levels of the Long Room. Another two voids in the ground-level slab, which required simply subtracting the existing floor plate, supply natural light to the lower floor, which houses a Children’s Library and Teen Center.

“The subtractions ended up being more complicated than the additions in a sense,” says Elizabeth Leber, the partner in charge of the project for Beyer Blinder Belle. She describes how one of the more complex aspects of the project was the design of the new floor slabs for the Long Room. Those five floors were constructed with a long-span corrugated metal deck that is perforated for improved acous- tics. “It does all of the work in a very shallow depth and air gets distributed along the walls so we don’t have the drops of ductwork,” says Leber. “It’s a quiet detail and it was down to inches. The whole concept of the Long Room hinged on getting this to work, and therefore the capacity of books.”

Another behind-the-scenes effort to make the Long Room concept come to life involves fire prevention within the vast void space. Because New York building code defines any void that connects more than two stories as an atrium, the design team devised a solution to integrate automatically retracting shutters that can close off the fourth floor. In the event of a fire, that curtain drops down and the void becomes a two-story opening.

Upon entering the library, visitors encounter an internal street that runs from the Fifth Avenue entrance to the welcome desks. The building’s existing structural steel columns became a dramatic element, painted in dark brown and uplit to guide visitors into the library’s public spaces. The columns are also used to structurally hang expansive work and display tables throughout the space. An existing mezzanine level was completely reshaped and hung from the level above using structural rods and columns.

Houben and team knew that no transformation would be complete without making a public facing gesture on the building’s exterior as well. Noting that city rooftops in the United States are often dedicated solely to mechanical equipment, Houben says, “I really wanted to use the roof.” With a design fondly named the Wizard’s Hat for its green chapeau-like form visible from the street, SNFL’s rooftop now supports a flexible 268-occupant conference and event center. An L-shaped roof terrace runs above the 40th Street and Fifth Avenue facades and includes a roof gar den and indoor café.

Silman designed reinforcements of the existing roof framing at various locations to support the loading of the new vertical addition. The new addition itself was designed on a platform of new steel supported on new columns that align with existing column locations. To allow for longspan spaces, the steel-framed addition has columns spaced 20 to 60 feet apart. The floors and sloping roof are supported primarily by a combination of steel brace frames, moment frames, and trusses, concealed within the finishes and the mechanical service levels above. The mechanical levels and the amenities below are topped with the hat, which reaches 184 feet above street level and is clad in factory-painted aluminum panels to mimic the patinated copper roofs of two 1904 Beaux Art rooftops visible from the terrace.

With new sightlines across Fifth Avenue to the Stephen A. Schwarzman Building and surrounding skyscrapers, the SNFL branch is perhaps more at home among its neighbors than it has ever been. Though the library had undergone small renovations in the past, the architects and patrons agree that the building, benefitting from the design flexibility of the original building’s steel frame, is finally living up to its full potential as a community hub. “It didn’t fully become a library until we did this renovation in a sense, though culturally it was beloved,” says Houbin. “It is a testamentto how an older building can be reimagined.”

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In the two years after Columbia dedicated the Manhattanville property in fall 2016, the university constructed three buildings and an outdoor plaza in quick succession. The newly opened Henry R. Kravis Hall is part of the campus’s most recent growth spurt. Designed by Diller Scofidio + Renfro (DS+R) in collaboration with FXCollaborative, the 11-story structure further embodies Columbia’s commitment to community integration, thanks to a scintillating facade that reveals the comings and goings of students and faculty.

Kravis Hall is one of two buildings that make up the new home of Columbia Business School. It faces the eight-story David Geffen Hall, also designed by DS+R and FXCollaborative, across a one-acre park designed by James Corner Field Operations. The pair of buildings comprises 492,000 square feet in total.

According to DS+R associate principal Miles Nelligan, Kravis Hall’s facade is the outgrowth of Columbia Business School’s desire to buck another tradition of higher-education buildings, namely the separation of faculty offices and student spaces. Inspired in part by guaranteed public access to the ground floor, Nelligan recalls that the design process “started with some very passionate conversations about breaking down spatial and population hierar- chies; we were encouraged early on to integrate all the school’s populations into one project.”

To ensure that students and professors would commingle outside of the classroom, the design team organized Kravis Hall into alternating floors
for learning and faculty use. Arup, which consulted on the project’s structural engineering, envelope, and facade, devised a so-called skip-truss system
to support that configuration. The overall building structure comprises ASTM A992 Grade 50 beams fastened to steel columns on composite floors, with webs placed throughout the grillage for additional bracing; the webs greatly increase in frequency on faculty floors to support the classrooms and other wide-open spaces on student floors.

“There was an architectural interest and a client interest in shuffling the buildings into layers. We thought it would be interesting to do the same with the structure,” says Arup principal Dan Brodkin, who adds that modular, highly partitioned faculty offices lent themselves to nesting within the more robust structure. Columns are typically W34 sections; beams range from W12s to W30s; and W10s, W12s, and W14s make up the webs. The system ties into the steel of an underground structure that had been commissioned separately.

Recognizing that professors or students could sequester themselves even in a layer-cake scheme, DS+R and FXCollaborative also pierced the building with two visually distinctive staircases whose landings are surrounded by multipurpose spaces. “This was a reaction to how and where education takes place in academic buildings, which is not only in the classrooms.

It’s about interactions, the time outside class, the group work, the socialization,” Nelligan says of transforming conventional circulation into a verti- cal quadrangle. The routes inserted along Kravis Hall’s west and east elevations are respectively earmarked for faculty and student movement. Because students tend to linger on campus despite not having a domain to officially call their own, landings that radiate from the student stair are especially commodious.

Both the alternating floors and unifying stairs are legible to passersby. Faculty floors are wrapped in a curtain wall whose vision glass includes a white ceramic frit on the exterior, which lends the surface a milky quality while modulating incoming daylight for the perimeter faculty offices. Student floors are finished in transparent glass planes that are inset from the floor plate’s edge. The two stairs employ the same code, moreover: the faculty stair is expressed on the west elevation as a fritted-glass plane that zigzags among the horizontal wedges, and clear inset glass wends up the east elevation to reveal the student stair. As Nelligan puts it, “The building is very honest about what’s going on inside.”

That the facade steps in and out alongside the alternating floors confirmed the need for Arup’s skip-truss structure, says Jeroen Potjer, a senior structural engineer at the firm: “We couldn’t place columns directly at the perimeter, because of the layered composition. The skip system is always perpendicular to the face, to accommodate those long cantilever conditions of approximately 12 feet.” Arup also conceived a “ladder-truss system” to support those areas of glass that span multiple stories. In these places, two parallel ASTM A500 rectangular HSS are set in from the facade, and the tubes link via horizontal elements.

The project team then engaged W&W Glass in design-assist to create Kravis Hall’s communicative skin. “Design assist helps us with constructability and installability,” W&W project manager Ryan Malynn says of the delivery method, which inserts manufacturer feedback early in the design process. Malynn adds, “Because this building has a lot of unique setbacks and deep soffits, we were more in control of how our steel connected to the structure.”

After performing its own load analysis, W&W worked with Arup to introduce kicker angles and other stiffening techniques, so that Kravis Hall’s structure could support the company’s preferred configurations and connections. In parallel, W&W determined to execute the faculty facades as unitized curtain walls. Meanwhile, the transparent glass of student floors are stick-built window walls that have their own structural steel support system at the head and concrete curbs at the sill. “Because of the way every other floor steps back, every single floor has its own starter track,” Malynn also notes of the alternating systems. (Storefront glass wraps the ground floor.) All standard systems absorb thermal, seismic, and differential movements of approximately 1 inch, according to Malynn’s fellow project manager Matthew Keefe.

The stick-built walls are hanging systems, in which the steel head dead-loads the panels. Keefe points out that W&W also had to take into consideration large live load and drift movements, given that the three east-facing walls abutting the student stair span two or three stories. The company responded by adding aluminum-clad, ASTM A500 50 KSI rectangular HSS mullions to the glass, setting them into the starter tracks with base anchors. The mullions were set in section and spliced in the field.

“It was quite a road to travel, to create a system that can adapt to all these bespoke situations,” Nelligan says of W&W’s efforts. Of making build- ing activity and the urban context visible to one another overall, the architect adds, “at Columbia Business School, you know you’re in New York.”

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By September of 2018, the fast-tracked project was complete. Rather than try to expand the foot”print of the existing Collegiate Gothic-style build”ing, MBB designed an efficient and complementary structural steel addition, joining the two structures with a shared core. (In 2019, the architects mod”ernized classrooms and upgraded systems in the 1923 building.) “You try to build as economically and quickly as possible and steel enabled us to do that,” says Jeff Murphy, a founding partner of MBB. “Instead of having an extensive basement, we chose to do a small basement for some of the mechani”cals, but by and large we built this slab on grade. It was really just steel going into footings on most of the building.”

The new five-story, 97,000-square-foot addition contains classrooms, cafeterias, a gymnasium, and instructional and health space, helping to disperse the school’s 2,000 students and serving as an im”portant community hub and social services provider. “One of the things that was pretty compelling about the project is that this part of Queens is in dire need of school seats,” says Murphy. The elementary school was one of the worst and most visible victims of overcrowding—a result of the closure, demolition, and consolidation in the 1970s of nearly 100 public schools in New York City as the population dropped and the city’s finances tanked. When enrollment began to climb again in the 1990s, the school con”struction budget couldn’t keep up. When Murphy’s team began its design process, P.S. 19 had been using dilapidated 20-year-old classroom trailers located on the former playground to accommodate the diverse student body.

In order to speed up construction of the new building, MBB chose a precast panelized facade clad in brick. Canted windows appear to match the scale and fenestration pattern of the 1923 building with the addition of exaggerated precast concrete frames. One of the biggest challenges of the project, according to Geoff Smith, an associate with structural engineer Silman, was the connection of the precast facade panels to the structure—the engineers had planned for them to hang column to column, bracing back to the slabs. But due to a mix-up with the manufacturer, the panels had to be braced back to the steel structure. “So the steel had to be reanalyzed for torsional [stress],” says Smith. In addition, the structure had to be oversized to sup”port the weight of the panels’ brick cladding.

But perhaps the most challenging constraint was the fact that the north elevation of the new building is adjacent to the elevated, rumbling 7 subway line along Roosevelt Avenue. This made erecting the steel structure a laborious process, says Murphy, requiring flagmen provided by MTA and specialized staging. “They had to have [steel members] on the street, ready to go up, but in between when trains were running,” he adds. A robust acoustical treat”ment of northern elevation included a baffle wall and STC-rated windows, allowing students to see, but not hear, the passing trains. Murphy and his team then placed the most active programs to the north, such as the cafeterias, stairs, and open-air play roof. “One of the things that the teachers and staff were so delighted with is that we were able to make the noise go away,” says Murphy.

The cafeteria in the old school building was cramped and poorly planned, so part of the brief for P.S. 19’s addition was two generous, column-free dining rooms. The architects placed these on the ground floor, adding a band of glazing that creates a friendlier and storefront-like interface with the busy neighborhood. A playground on the roof of the northernmost cafeteria has a steel frame enclosed with steel mesh. This area required the design team to perform vibration analysis because it cantilevers from the building below.

Three oversized steel stairs—on either end of the new building as well as in its center—were another major design element, helping to choreograph the 2,000 students through three lunch periods. “We ended up having to make the connection to the new building through a stair in the old building,” says Murphy. “That switchover had to be done in a weekend. The new stair in the new building could be used right away as we decommissioned the stair in the old building.”

Murphy’s team brought warmth and cheer to the addition with pops of color for orientation, wood ceilings in the lobby and corridors, and wood-clad seating niches in hallways for studying and social”izing. A bright mosaic mural in the lobby depicts nearby Flushing Meadows Corona Park, the site of the 1939 and 1964 World’s Fairs.

Together, the two buildings feel like a cohesive whole, and give students, teachers, and staff the space they need and deserve after decades of neglect. The massing, scale, and materiality of the addition are a pleasing foil for the 1923 school build”ing. “We showed deference to the old building, but we tried to make the new building express today’s values and technology,” says Murphy.

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Moving patiently between tasks, getting the details right efficiently, and taking the time to explain them to visitors, Davis typifies the personnel working on this project: on top of his game, at ease with the complexities of the job. His and his colleagues’ expertise is part of the reason One Vanderbilt is ahead of its projected schedule and under budget. (Demolition at the site began in 2015, the groundbreaking occurred in October 2016, and the topping-out date was originally set for January 10, 2020; the team reached that milestone on September 19, 2019, and estimates for the temporary certificate of occupancy now run from August to October 2020.) As the key factor making this pace possible, says Edward DePaola, president and CEO of Severud Associates, ‘I think it’s a combination of the right design and construction team,’ and ‘they’ve got to put the best people on it…. It’s real dedication and the ability to think and perform way beyond what’s normal.’

Coordinated design and construction planning, DePaola points out, sped this project from the outset. As he and others noted at a panel discussion about One Vanderbilt for the American Institute of Steel Construction (AISC) on September 26, this was neither a design-bid-build nor a design-bid project, but what he calls ‘just an enhanced design with detailing.’

‘The project wasn’t simply fast tracked; it was ‘faster’ tracked,’ said KPF’s Technical Director, Andrew Cleary. Since the Project schedule required early bid sets to be issued well in advance of a more typical fast track timeline, the design team worked with Tishman and detailers from the major trades during the early design phases to expedite development of a coordinated parametric model. ‘If we identified and resolved one conflict before construction began, we were able to justify the price of the detailers being engaged pre-award.’ Cleary noted. ‘If we resolved two conflicts, we were already ahead of the game. The fact that a project of this complexity has repeatedly achieved all the major construction milestones on time is a clear testament to the tight collaboration that the Design and Construction Teams forged from the outset of the design process.’

General contractor Tishman hired independent detailers for each trade before subcontractors were on board, DePaola recalls: ‘We had a structural steel Tekla modeler working for Tishman, actually building the Tekla model as we were designing…. We supplied only up to Revit; we gave them Revit information; they did Tekla, which is much more accurate than Revit as it relates to exact beam lengths [and] ability to put all the bolts and welds right into the model.’ When Banker Steel and other contractors came on board, the Tekla model saved them all months of work. ‘Steel was going to be fabricated,’ DePaola says, ‘so that [the other subs] had to be thinking of things a year in advance of when they normally would, and everybody pulled their weight.’

This advantage required unprecedented earlyphase coordination, beyond what many teams could handle. Mechanical engineer Christopher Horch of Jaros Baum & Bolles (JBB) recalls the extensive revisions addressing intertwined architectural and business concerns. As a spec developer building, One Vanderbilt needed extreme flexibility from the MEP standpoint, depending on which tenants would sign on, now or in the future; as a major tower located next to Grand Central Station, it needed to preserve sightlines and street-level plaza space. The electrical transformers are located alongside the large chiller plant and other major MEP systems on the 12th floor rather than at sidewalk level, and KPF designated a 5-foot plenum on the perimeter of mechanical floors (the fourth, fifth, and 12th), along with vertical intake/ exhaust slots by Permasteelisa rather than conventional large gray louvers, so that these floors would visually read no differently than office floors by day or night. With all of those moves, square footage for MEP was squeezed.

Consequently, Horch says, ‘during our schematic design phase, they were changing the building almost on an hourly basis,’ at one point increasing floor-tofloor height by 2 feet at the 12th floor. ‘It was a big change, but it was able to be absorbed, because we were only in DD [design documents], and those things get flushed out over time. If we had not done that level of detailing, we would not have caught it until construction, and it would have had a major impact on the schedule and cost.’ The efficient procedure also gave bidding contractors such confidence, he adds, that ‘the bids came back … within a few percentage points of each other on all trades from an MEP perspective, which is also unheard of.’

‘When Tishman put this out for bid, they gave them the Tekla model for the whole building,’ DePaola says, ‘with a handful of typical connections throughout the building, but with the bottom six levels detailed, and they said to the bidders, ‘This is it, guys. If you can’t do these details, if you’re going to come back and say you want to change X, Y, and Z, you’ve got to tell us how much longer that’s going to mean to your schedule, compared to if you took it exactly the way we gave it to you. And speak now or forever hold your peace.” The contractors made the commitment, enduring weekly meetings for a year and a half, locking in details down to the level of coordinating structural steel and ductwork in elevator lobbies. ‘We were asking them to commit to that geometry when they were in DD, and most architects wouldn’t even be thinking about the lobby elevators until near the end of construction documents.’

One Vanderbilt is a hybrid building with a concrete core and a steel frame around its perimeter. It thus needed to solve the recurrent problem of steel and concrete components rising at different speeds. DePaola recalls other projects that had to give concrete contractors a head start on steel contractors, leading to scheduling challenges as well as structural ironworkers safety objections to working below another trade. Here, Severud drew on its experience with Philip Johnson and John Burgee’s IDS Center in Minneapolis (1972), a pioneering project in steel-first construction, to erect steel ahead of rebar, interior and exterior formwork, and concrete shear walls. ‘We worked out a different type of form system, so that the inside is a climber and the outside is handset,’ DePaola recalls. ‘On this job Navillus did the concrete, and they were right there; we never slowed down. Everything worked like clockwork.’ The project’s foundation work included a 4,200-cubic-yard single continuous pour in February 2017, a 27-hour operation that marked the largest such pour in the city’s history—’like somebody coordinated a ballet,’ DePaola told the AISC audience.

One Vanderbilt will be New York’s fourth highest building (after One World Trade and two ultrathin residential buildings under construction on 57th Street). Its adjacency and underground connection to Grand Central make it the ultimate in transitoriented development—particularly when the Long Island Rail Road enters the station under the East Side Access plan a few years from now—as well as a high-visibility emblem of the newly rezoned Midtown East commercial corridor. Though any commercial building on this scale attracts scrutiny over pedestrian traffic, shadows, and aesthetics, One Vanderbilt’s design respects its Beaux Arts neighbor and its street-level neighborhood, forgoing maximum square footage in favor of a tapered form admitting light onto the street and the new car-free Vanderbilt Plaza, attaining a floor-area ratio of 30 (and realizing higher target rents on high floors to offset area sacrifices, based on view analyses from real-time parametric analyses and drone photographs; ‘once the leasing guys saw this,’ Cleary said, ‘you could hear the breath getting sucked out of the room’). The building looks to be a model of 21st-century integrated management as well as advanced thinking in design, sustainability, and habitability. When it opens next year, its managers won’t be the only ones whose breath is taken away.

Editor’s note: This is the first in a two-part series about One Vanderbilt’s construction. The second part will appear upon the building’s completion.

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The chief reason the 1955-vintage Tappan Zee Bridge (TZB) was financial. It was the closest site to the city outside a 25-mile radius from the Statue of Liberty; by law, any bridge within that area would be within the Port Authority’s jurisdiction, meaning New York and New Jersey would split the toll revenue. Gov. Thomas Dewey preferred to direct that stream toward the newly created authority for the New York Thruway. Hence, drivers got a bridge that sent them over the water for three miles but kept the tolls in the state.

Engineered with ingenuity and frugality during a Korean War-related materials shortage, the TZB used a military structural technology known as Phoenix caissons, a series of eight buoyant concrete breakwaters set in riverbed rather than on rock, the brainchild of chief engineer Emil Praeger. The TZB was planned to last 50 years and was showing its age well before the 2007 collapse of Minnesota’s I-35W bridge focused national attention on decaying infrastructure. Originally designed to carry fewer than 40,000 vehicles per day, it was averaging 138,000 by the early 2000s (roughly the same capacity as the deadly I-35W bridge), and its nonredundant design meant that failure of any member could put the entire bridge in danger. Construction attorney Barry LePatner, author of the infrastructurehazards exposé Too Big to Fall (Foster Publishing, 2010), referred to the TZB as the “scary of scaries.” With its narrow lanes and no shoulders, by 2007 it also had over twice the average collision rate per vehicle mile as the rest of the Thruway system.

Its replacement, the twin-span Gov. Mario M. Cuomo Bridge, represents a different kind of innovation. It couldn’t have moved closer to the city—the site is effectively locked in by approaching roads and regional development since the fifties—but its design and construction reflect the dramatic progress in
the field and the evolution in civic priorities since the Eisenhower era. Each span has four lanes for general traffic, a breakdown/emergency shoulder, and a dedicated bus lane; the westbound (northern) span also gives pedestrians and cyclists a 12-foot shareduse path with six overlooks offering river views.

Like many striking bridges built in recent years (including, locally, the new Kosciuszko span featured in Metals in Construction’s Spring 19 issue), the Cuomo Bridge uses a cable-stayed design, once arresting, now nearly as familiar as it is economical. The project’s innovations are in realms beyond the striking aesthetics: ease and pace of construction, Intelligent Transportation Systems (ITS), structural health monitoring (SHM), and attention to long-term environmental effects. The site’s multiple challenges have once again been mothers of invention.

“The iconic Governor Mario M. Cuomo Bridge is a state-of-the-art transportation facility that will meet the needs of Hudson Valley residents and visitors for the next century and beyond,” comments project director Jamey Barbas of the Thruway Authority. “This landmark crossing symbolizes New York’s resolute commitment to transforming and modernizing its infrastructure.” Fast-tracked as a High Priority Project by the Obama administration, it has carried full bidirectional traffic since September 2018.

For a project of this scale, after issuing an RFP in 2012, the New York State Thruway Authority chose a design-build strategy and a multidisciplinary consortium, Tappan Zee Constructors (TZC), comprising engineering and construction firms Fluor, American Bridge, Granite Construction Northeast, and Traylor Brothers, along with design firms HDR, Buckland & Taylor (now part of COWI), URS (part of AECOM), and GZA. (The TZC project team collectively contributed some of the information for this article through the Thruway Authority in lieu of personal interviews.) It is one of the nation’s largest design-build transportation projects, marshaling this method’s efficiencies to overcome the site’s unique challenges.

The Hudson Valley’s geology called for extensive geotechnical studies, including more than six dozen soil borings of the riverbed, revealing layers of clay, silt, sand, and glacial till covering bedrock below the river, with a deep valley of clay under the western half. This led the designers to bypass buoyant caissons and select a structural system based on piles consisting of steel tubes filled with steel-reinforced concrete; the process used over 30,000 tons of rebar. Most piles rest on bedrock, while others (longer and with greater surface area) use the friction of the deep clay to create supportive tension, which TZC estimates will withstand at least 100 years of load-bearing.

The piles of the main span above the deep-water navigation channel are unified in pile caps, the largest of which is longer than a football field, consolidating the strength of scores of piles into a single structure. Smaller pile caps support the approach spans on either side of the main span. In 2013, TZC performed load testing with massive weights, up to 7 million pounds, the equivalent of about 2,000 cars, ensuring that the pile system had adequate carrying capacity before construction began. Lowering the huge caps precisely and in sync required a computer-guided jack system, factoring in the river’s tidal flow.

The eastbound span is 87 feet wide; the lane for self-powered users makes its westbound counterpart 96 feet wide. Eight 419-foot concrete towers stand at five-degree angles from vertical, leaning outward to create a distinctive aerial profile and bearing “192 stay cables that would stretch 14 miles if laid end-toend,” according to the TZC team. The cable-stayed area is 2,230 feet long, and the cables support a total of 74 million pounds of steel and concrete.

TZC used modular construction procedures, preparing major segments of the foundations, roadway, and superstructure safely off-site on land, including structural steel assemblies up to 410 feet long. The largest of the project’s cranes had a 328-foot lifting arm capable of raising loads up to 1,900 tons. TZC purchased this huge device, originally built for use on the San Francisco-Oakland Bay Bridge and named the Left Coast Lifter, and moved it 6,000 miles from California via the Panama Canal, renaming it I Lift NY en route before it reached New York Harbor in January 2014. Months of testing and customization prepared it for service on the Hudson that April, raising nearly 100,000 tons of structural steel (including 140 girder assemblies and four main span crossbeams) as well as precast concrete foundations, substructure, and 120 road deck panels. After the first span opened in August 2017, I Lift NY also saw action removing sections of the old TZB; its final operation in May 2019 was to remove the old east anchor span after its controlled demolition that January, part of the process of disassembling the obsolete bridge for recycling and reuse at other locations across New York State. TZC credits I Lift NY with shortening construction time from original estimates by months and saving millions of dollars on the project.

Today’s bridges take active roles in guiding traffic, not just carrying it. The Cuomo Bridge’s ITS, a complex of sensors and communication channels, monitors conditions on the twin spans and automatically informs Thruway Authority staff of disruptions. Information about collisions, closed lanes, winter pavement conditions, or other sources of trouble goes out to motorists through electronic signs on the bridge and landings, directing drivers away from hazards and reducing risky last-second lane shifts. The ITS also connects the Thruway Authority with law enforcement, first responders, and tow-truck operators. As a component of the authority’s wider traffic-control network, the ITS helps synchronize both preventive maintenance and repair work, reducing disruptions.

Information technology also generates useful data about the bridge itself. Over 300 sensors in the SHM system—a complex of inclinometers, ultrasonic distance censors, fiber optic gauges, 3D accelerometers, and GPS instruments – measure corrosion, temperatures, climatic conditions, vehicle weights and counts, cable strain, tower sway, and expansion joints’ reactions to load patterns and vibration. Gantry-based automatic tolling, by either EZPass or photo/mail systems, spares drivers a slowdown to fish for cash. The roadway lighting comprises dark-sky-compliant LED fixtures, cutting light pollution in the scenic Hudson Valley while saving an estimated 75 percent in energy costs over older lighting technology.

In a region with history of environmental damage and remediation (the bridge is downriver from General Electric’s dredging operations for polychlorinated biphenyls), the impact of construction on local ecosystems has been a key priority. Construction equipment met strict Environmental Protection Agency emissions standards, using ultra-low-sulfur diesel fuel and tailpipe particulate filters. To control underwater noise and vibration during pile driving, the crew created a bubble-curtain system, sliding aluminum rings over pilings and pumping pressurized air through the rings to create a cloud of bubbles that absorbed the energy of impact, reshaping pressure waves, lowering the noise level by more than 10 decibels, and deterring fish from swimming into the hazardous area. Dredging was timed to avoid interrupting spawning and migration seasons. The Thruway Authority consulted with scientists from the NY Harbor Foundation’s Billion Oyster Project and placed more than 400 oysterreef structures in a five-acre zone near the bridge to support restoration of this ecologically beneficial filter-feeding species. A nesting box atop one bridge tower has attracted peregrine falcons, another important species whose prey includes pigeons; since pigeon waste is acidic enough to corrode steel and concrete, the falcons’ deterrent presence is a win/ win for humans and birds.

One substantive critique of the bridge addresses a decision made on a political level, not by architects or engineers: one of the 21st century’s largest projects chiefly accommodates the dominant transportation mode of the 20th. Public transit on the bridge is limited to bus service; both a planned bus-rapid-transit line and the pedestrian/bike path have been delayed. Early studies, including 2011 Ove Arup reports on cost estimates and feasible alternatives prepared for the state Department
of Transportation, the Thruway Authority, and the Metropolitan Transit Authority/Metro-North, evaluated structural options that would include RocklandWestchester commuter rail; the February 2014 final recommendations by the bridge’s Mass Transit
Task Force notes that commuter and light rail were considered but “included as long-term recommendations.” TZC reports that the bridge “was built with the structural capacity to handle light/commuter rail in the future. The future rail line would be located between the two spans.” This isn’t the first or last time financial concerns led to a decision that delayed a more future-oriented design component. But the most intelligent transport systems in the long run, many environmentalists, urbanists, and economists maintain, might not involve automobiles at all. While Hudson Valley residents enjoy driving across their new bridge, they may also dream of the day it offers them other transportation options as well.

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