The tower under construction at the corner of Sixth Avenue and42nd Street, near Times Square in midtown Manhattan, may for a short time have the distinction of being the second—tallest building in New York City Its developers. however, are aiming for more than just another skyscraper. Their goal: to create the world’s most “environmentally responsible high-rise office building
The $1-billion building, known as One Bryant Park, is being developed by a joint venture of the Durst Organization, of New York City, and Bank of America, which is based in Charlotte. North Carolina, and will serve as the New York headquarters of the bank, which will occupy roughly half of the 2.1 million sq ft. space. The occupied portion of the structure will rise 945 ft, but its spire will reach an elevation of I,200 ft.---just 50 ft. short of the city’s current record holder, the Empire State Building. Yet it will have only 54 stories-far fewer than one might expect for such a tall tower. (The Empire State Building, by comparison, has 102 stories.) The reasons are directly related to the environmental goals of the project.
For one thing, fewer stories mean more space for mechanical systems between the floors. The building’s under-floor air distribution system- designed to maximize efficiency and to give occupants more control over airflow-demanded that the structural floor-to-floor heights reach a minimum of 14.5 ft, more than 1 ft higher than in a typical office building. The finished ceilings are 9.5 ft high to increase the penetration of natural light, says Robert Fox, a partner of the huilding’s New York City-based architect, Cook+Fox Architects. Llp.
The building will also incorporate a number of systems designed to save water and electricity . For example, nearly all the storm water from the site will be captured and reused, and wastewater will be recycled as well. Additionally, an approximately 5 MW co-generation plant, located on-site, will use waste heat to produce much of the building’s electricity-the first time a New York City high-rise has relied on such a system, Fox says.
Mechanical and electrical engineers Jams, Bauni & Bolles, of New York City, played au important role in the design of the water and energy-saving systems, which will also include a thermal storage system, water-less urinals, and, possihly, an anaerobic digester to convert food waste into electricity. The developers are hopeful that the buildmg’s numerous innovations will earn it platinum-level certification from the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) program --a distinction few buildings, and no high-rises, have yet achieved. Structurally, the building is a hybrid, having steel framing but a Concrete core. It’s a good combination of materials” says Edward DePaola, P.E., a principal of the New York City based structural engineering firm Severud Associates, who notes that the system combines the stiffness of a concrete core with the speed of erection of a steel frame, thus reducing costs. The hybrid design saves a significant amount of steel, DePaola adds, because the diagonal bracing that would normally he required in the 80 by 80 ft. core is eliminated.
For a means of erecting the building, the Severud engineers turned to a system originally developed by the firm in the late I 960s and early 1970s in which the steel framing is erected up to 12 floors ahead of the concrete core. Originally developed as a means of speeding the high-rise construction, the system will be revived at One Bryant Park so that the ironworkers will not have to work below the concrete workers, DePaola says. The system was previously used to construct the IDS Center, in Minneapolis, he says.
Complicating the structural design, all but one of the perimeter columns are sloped, contributing to the building’s faceted, crystalline appearance. Because the columns begin to slope at different elevations, every floor is different, explains Andrew Mueller-Lust, P.E. the project manager for Severud Associates. The design team had to take care to resolve the horizontal forces created by the sloping columns by transferring those forces to the core via the floor framing. ‘Nothing is easy on this building,” Mueller-Lust says.
The project. which also includes the restoration and reconstruction of the 500,000 sq ft. Henry Miller Theater, is scheduled for completion in 2008. The building will probably reign as the second tallest in the city for only a few months, however, because the Freedom Tower, to be constructed at the site of the former World Trade Center towers, will supersede even the Empire State Building.
—Jeff L. Brown
Civil Engineering Magazine
October 2004, (pgs. 12-14)
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