11 Times Square Built Concrete Core First
Eleven Times Square, the last building to go up as part of the Times Square redevelopment project and the first major building in New York City to feature a poured-concrete core that was erected prior to the steel frame, is on schedule for completion in 2010. This precedent-setting development is likely to lead to the concrete-first method being used in future construction projects in New York City.
The concrete-first method has long been used in other markets and throughout Europe, but resistance to it by New York’s laborers has traditionally been strong, mainly because of safety concerns. This time, however, the developers were able to get the labor unions to buy into the idea-and by all reports, Eleven Times Square has changed a lot of minds. The 40-story, 1.1 million-square-foot project has gone off with no major accidents-a couple of months ahead of schedule, in fact-at a savings of about $30 million compared to what it would have cost using traditional methods. It’s designed according to LEED Gold specifications, and its owner, SJP Properties, claims that it will be one of the safest and most efficient buildings in the world.
Eleven Times Square’s architectural features include floor plates that expand as the building rises, as well as six tenant-exclusive terraces on the tower. Seven column-free corner offices will be available on every tower floor, with panoramic views of the Hudson River, Times Square, and the Empire State Building. The base floors are the largest under construction in Midtown: 41,000 square feet each.
If the project has problems, they’re in the leasing, not the construction. At last report, the building had yet to sign up its first tenant, although CEO Steven J. Pozycki reported to the New York Times on October 4 that there is plenty of serious interest. SJP had hoped to start signing up occupants in mid-2008, and there was talk that rents for the cheapest space could top $100 per square foot. But the company recently conceded that it would be “real happy” with rents in the $70s.
How do you build a concrete core ahead of-and completely independent of-the structural steel frame? Why is it advantageous to do so? According to Richard Wood, president of Plaza Construction, it’s done by erecting a self-climbing form-a gigantic mold, in effect-on top of footings, with reinforced steel placed inside it. Concrete is poured into the form, and when it’s dried, hydraulics lift the form up to a new point, and the process is repeated.
“Within the concrete,” Wood explains, “flush to the face of the form, are flat plates of steel with sheer tabs welded onto them, and bolt-holes creating the attachment for the beams that will follow. The trailing platforms are part and parcel of the structure of the forming system. As the system is hydraulically lifted, the platforms go along with them so they’re constantly climbing the building.”
At Eleven Times Square, the foundation contractor, Urban Foundation/Engineering, got started on the concrete core before the foundation was completed and while the steel was still in fabrication. During this process, the steel framing followed as soon as the bottom of the climbing forms cleared the embedding. This tightly organized system allowed completion of the core in the shortest possible time.
“This system is advantageous because these forming systems allow you to better control the quality of concrete and the schedule of the pours are not dependent on other work,” Wood explains. “This concrete core is in essence a building unto itself, a well protected and secure core area that serves multiple purposes, the most important being to create the lateral stability of the structure. It creates a safe zone, after occupancy, and provides for safe egress.”
Steel, being light and flexible, requires some sort of bracing system, which stiff, heavy concrete provides, Wood says. Moreover, the strength of the concrete core enhances the building’s efficiency by drastically reducing the need for columns. Thus, floor plates can be created that will work well for both open-plan and office-intensive layouts. The core encloses all the building’s critical elements, including extra-wide stairways, elevators, utility risers, and the building’s command center. Mechanical, electrical, and telecommunications rooms for each floor are fully enclosed within the core walls, which results in greater security and reduced noise.
Eleven Times Square was particularly suited to the core-first option, says Wood. According to him, SJP Properties chose this method based on the configuration of the core: a straight–up configuration that was especially receptive to the self-climbing, forming system. PERI, a manufacturer that has subsidiaries in more than 50 countries, provided the climbing forms.
“These forms are customized for specific projects,” Wood says. “The forming system is not just the form itself, but the platform that the trades work from, plus storage for materials that are introduced into the sheer wall as it climbs vertically. The system creates a self-contained secure area.”
The concrete core, Wood adds, was made of locally sourced material, and most of the reinforcing steel was recycled-thus boosting the building’s LEED rating considerably.
Although many observers feared that the concrete-first method would bring objections from labor, it turned out that the trades gave enthusiastic backing to the plan, according to Wood.
“The unions helped create the opportunity for the building to be built this way,” Wood says. “There had been concerns about safety, since Manhattan is such a confined space and people would be working under those climbing forms. But once we had addressed those concerns, the trades were all very positive about cooperating with us to make a project like this succeed in this city. Their professionalism and quality of work were bar none the best I’ve ever experienced, and this was a great example of how the labor-management gap can be bridged. It was none too soon, since market pressures have created a need for labor and management to be creative to reduce costs and keep the industry moving.”
Bob Walsh, business manager at Ironworkers Local 40, admits that there was some push-back from his workers, but they finally decided it was better to be on the team, and have some say in ensuring safety.
“If we said no, who’s to say the developers would not have gone with an all-concrete building?” he asks. “This construction method maybe didn’t suit everybody, but I told the union, ‘There’s change coming, fellows, and we have to change with the times or get left behind.’
“The main concern was the safety factor,” Walsh continues. “We usually don’t have people working above us, and when the core goes up and the forms are released there are always going to be falling objects: chunks of concrete, pieces of wood, and so on. There were a couple of little problems at first, but we basically took care of it with a catch-all net.”
Of course there was also concern about the extensive use of concrete: the union would have preferred an all-steel building.
“That would have meant more work for our union,” Walsh says, “but we preferred to be there in some capacity than not be there at all.”
According to SJP, the unions, site safety experts, and subcontractors worked together to develop a comprehensive safety plan. Egress was a major issue, which was addressed via a dedicated hoist for the core construction and a temporary stair hanging from the formwork, which accessed multiple levels at any given time, giving direct access to the permanent stairs-which were installed immediately to the underside of the form system at each jump. Plaza also employed two full-time safety managers to simultaneously monitor the core and steel construction, and implemented a safety reward program for the trades.
William Kell, chief estimator and project manager for Sorbara Construction Corp., based in Lynbrook, NY, who oversaw the construction, says that the conflict-such as it was-was easily settled once the union saw how the project actually worked.
“This building is the first of its kind in New York City, but if you go anywhere else, this is the way buildings are built,” he says. “We were able to demonstrate to the ironworkers that this method is safer, in great part because it gets done faster.”
“Speed is one safety advantage; the fact that there’s less steel is another; thirdly, it’s safer all around because the concrete and steel are in effect encased within a cocoon. You really can’t see it during forming and placing. Could some accident happen? Of course-but it’s less likely, using this system.”
According to Kell, it’s a sure bet that more buildings will be built this way, in all five boroughs.
“There’s nothing faster, safer, and more economical,” he insists. “Seven World Trade Center was a similar job, but in that case the self-climbing equipment wasn’t allowed to be used, so we had to take that forming system and go underneath the steel: a very antiquated method. But this time, numerous developers and construction experts took field trips to this site, and I believe they were well enough persuaded so that other major projects may go this route. This is the way to build high-rise buildings. There’s no good reason to go backwards.”
And Kell asserts that “tremendous savings” were realized across the board as a result of building the concrete core first, although he’s coy about providing a number. “I could quantify the savings,” he says, “but I won’t. Whatever edge I may have over the competition, I’d like to hold onto for a while.”
Article By: Joseph Dobrian PUBLISHED IN: nyinc DATE: November 17, 2009