On a continuous adrenaline rush, a hyperdedicated team working in the wings of Ground Zero has been bounding toward a goal once considered unachievable-completion of the $50-million renewal of the Winter Garden at the World Financial Center by the anniversary of the Sept. 11 terrorist attacks. The effort to repolish the architectural gem of lower Manhattan, a cavernous steel-and-glass skylight smashed close to smithereens by the collapse of the 110-story One World Trade Center, owes it success in large part to a brilliantly conceived exterior hoist-and-trolley system. The contraption not only sped the roof steel rehabilitation, it compressed the reglazing of nearly 60,000 sq ft of glass from the two years the job originally took into just 4.5 months.
Over the year, the cacophony of reconstruction noise at the grand atrium building has served as a welcome counterpoint to the somber strains issuing from the 16-acre crater across the street". This project provided a certain optimism everybody was so hungry for," says Craig Copeland, an associate in the New York City office of the Winter Garden's original and current architect, Cesar Pelli & Associates. "It inspired everything," he adds.
|OVER THE TOP Trolley system let glaziers do their work in just 4.5 months. (Photo courtesy of Turner Construction/NAT Valentine)|
The magnitude of the task only served to supercharge the workers. "We got 250% from these people," says James White, project superintendent for the WFC recovery team of Turner Construction Co., New York City, and the acknowledged mastermind behind not just the trolley system but the overall strategy for getting to the finish line by Sept. 5.
The rebuilt Winter Garden stands as a 110-ft-tall symbol of hope amidst the shattered lives and dreams of the area. And with its new glass entryway facing Ground Zero, it also is a giant welcome-back mat for the citizens of New York City and beyond. Beyond that, it has boosted the spirits of those grappling with the sticky issues of rebuilding, a process rife with emotions, politics, economics and countless agendas.
It is "a fantastic symbol for the planning effort," says Margaret Helfand, a principal of Helfand Myerberg Guggenheimer Architects, New York City, and outgoing chair of New York New Visions, a coalition of more than 80 firms and groups representing architects, planners, graphic designers and engineers that has labored without compensation to advise city and state officials on the area's renewal. Among its many accomplishments, NYNV designed, pro bono, the Ground Zero viewing fence, a portion of which is set to open Sept. 11.
Helfand predicts that with its new "front door" on West Street, which replaces stone cladding, the Winter Garden will become "the major public space downtown," and "much more important than it ever was before."
CRITICAL LINK. The $65-million Winter Garden, between West Street and the Hudson River, opened in 1987 as the centerpiece of the 8.5-million-sq-ft WFC (ENR 3/7/85 p. 28). One of the few "quality-of-life" indoor spaces in Manhattan, it is a critical indoor pedestrian link to mass-transit connections, both subways and ferries, to New Jersey. "It is the reason Cesar Pelli won the commission for the WFC in the first place," says Sabrina Kanner, a vice president of WFC owner Brookfield Financial Properties, and project manager for the rebuild.
The structure's four-story, U-in-plan base skirts the 192-ft-wide vaulted skylight, framed by architecturally expressed steel truss arches 15 ft apart. A 110-ft-tall glass window wall offers views of the Hudson River and New Jersey to the west.
Trusses are pin-connected into composite concrete and steel ladder columns along the sides of the garden. In the long direction, trusses radiate from an apse at the east end of the roof, across from Ground Zero. Loads go to drilled-in caissons.
Upon initial inspection of the damage, locally based Thornton-Tomasetti Engineers (T-T), the garden's original structural consultant, thought the building was unsalvageable. Many arches were damaged or partially down, as was the east facade and a large portion of the east floor framing. Most seriously, the system for lateral stability, a 350-ft-long, 50 to 60-ft-wide horseshoe-shaped horizontal diaphragm truss within the fourth floor, was heavily damaged at its most critical area, the 50-ft-long turning point at the curve of the horseshoe.
|NEW FRONT DOOR Dream team's (l. to r.) Zborovsky, Kanner, White, architect Rafael Pelli and Copeland in front of new wall. (Photo by Michael Goodman for ENR)|
Even more worrisome, says the engineer, the inner edge of the truss was still attached to its edge girder. But the breached girder had lost structural stability. If lateral forces were to push the horseshoe apart, the whole structure would have collapsed, says Leonid B. Zborovsky, a T-T principal involved in the original project and the repair.
If that had happened, there would have been damage to the 51-story Three WFC, to which the garden was attached for lateral stability through its horseshoe truss.
"Miraculously," says Zborovsky, a three-story pile of debris from One WTC, the downed pedestrian bridge that gave access to the garden from the WTC and the damaged Three WFC was propping the Winter Garden's broken horseshoe truss.
But the fire department, searching for survivors, was eager to remove the debris. Fortunately, T-T also was representing New York City's Dept. of Design and Construction as structural consultant at Ground Zero and was able to convince officials to leave the debris until workers could shore and brace the structure.
|VIEW IN Part of Ground Zero viewing fence is set to be done by Sept. 11. (Rendering courtesy of New York New Visions)|
From mid-September to December's end, crews from local construction firm AMEC and scaffolding contractor Atlantic-Heydt Corp., Brooklyn, N.Y., installed compression struts between the ends of the garden's roof arches and bracing at critical locations. Workers had to cut 5-ft-square shafts four stories deep through the thicket of debris to install shoring towers under damaged roof arches. The trick, says Zborovsky, was staging the work to prevent further compromise to the structure. During the operation, other than some broken glass falling, there were no secondary collapses.
Beyond T-T's structural assessment survey and shoring and debris removal, the city would not allow any work on the garden until January, when it turned the building back to the owner. "We couldn't get people to the site because the pieces of the corner of Three WFC, including One WTC steel, were dangling precariously over the Winter Garden," says White.
White, at Ground Zero since Sept. 13, didn't waste the waiting time. Hired for the garden's fine demolition and restoration, Turner used the "delay" to collect original drawings, procure replacement glass, order steel and lock up time for fabrication of replacement steel, stone and the curtain wall.
The earliest preliminary schedule for the Winter Garden redo called for completion by late October or November 2002. But Brookfield wanted the work done by the anniversary of Sept. 11, so White promised to finish by Sept. 5. With 350 activities, the schedule has not changed since Oct. 1, other than the east facade redesign, he says.
Turner's approach was to work in as many areas as possible at the same time and to get double duty from as many systems as possible. The "dance floor," a work platform built 67 ft above the Winter Garden's first floor, is an example. The platform provided a safety net for roof workers, protected workers below from falling objects and weather and gave workers roof access from the interior. Another example are the arch shoring towers. They helped support the dance floor, along with the horseshoe truss.
|UNDONE, REDONE Winter Garden damage was so severe that engineers thought it not salvageable and in danger of total collapse, threatening 51-story adjacent tower. (Photo by Michael Goodman for ENR)|
Last but not least, the trolley system deserves the most bows in the reconstruction. The inspiration for the system is that "it took two years to glaze the roof the first time and we needed to do it in four and a half months." says White.
Crews from Atlantic-Heydt installed the 375 x 225-ft structure up and over the Winter Garden roof last January. Beams spanning the roof to shoring towers on either side were located slightly offset from roof arches, which align with skylight mullions.
Beam flanges became the rail for the trolley rigs but the beams also supported damaged roof arches during their restoration. In an operation that lasted from February through April, ironworkers from the New York City office of Canron Construction Co. hung an arch off a beam while they cut out damaged segments, hoisted them away using a 450-ton crawler crane and welded in replacement sections.
In areas of zero arch damage, and then later after arches were repaired, workers hooked up trolley motors for placement of the skylight system.
Glass installation started in April on the west end of the garden and was completed by the end of July. Turner had four trolley rigs on the job, each measuring 12 ft deep, 25 ft wide and 10 ft in height. Thanks to a four-point suspension system, the rigs could follow the contour of the roof. Each rig contained a platform that dropped out and a small derrick equipped with suction cups to maneuver each 400-lb light of glass. "We would load the car in the morning and it would never come down until the day's end," says White.
When it was time to move a rig down the roofline to install another bay of skylight, workers would drop the rig onto the ground, roll it to the next bay, and hook it up to the next set of trolley beams.
|MISSING BACKDROP View of WFC from the Hudson River is minus the 110-story twin tower, One WTC. (Photo by Michael Goodman for ENR)|
In the early months, the logistics of getting equipment, workers and materials to and from the site hampered progress. "The roadways were blocked," says White, and the WTC work took precedence.
Turner worked closely with the Port Authority of New York & New Jersey, which owns the WTC site, and the city's Dept. of Design and Construction, "to gain some space," says White. Using carpenters and laborers, Turner even helped the city build command posts. Turner eventually found ways to get vehicles down West Street and over to the riverside promenade alongside the Winter Garden.
For the redo, Turner called upon firms involved in the original project, even the quarry in Italy for the stone flooring. Subs were hand-picked and though most contracts were not competitively bid, "we were not gouged," says Brookfield's Kanner. "People were glad to have something like this to work on [and] were generous with time and good will. It was a crazy, creative group."
By virtue of the Sept. 11 anniversary reopening, the Winter Garden has moved from the wings to center stage in the public's eye. "The Winter Garden represents all [that] we wish to embody in the development across the street," says architect Helfand, referring to Ground Zero proper. And with its new front door, she adds, "it is a demonstration that we can put things back and make them better."