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Of the many recently constructed high-rise office buildings in New York City perhaps none presented a greater challenge than the new Bear Stearns headquarters building, at 383 Madison Avenue.
The Bear Stearns Companies, Inc., a global investment banking, securities, and brokerage group, had outgrown the 1920s-era building on Park Avenue that had been its headquarters and wanted to take advantage of the amenities a newer building could offer, including column-free office space and a larger floor area for its securities traders. Engineered by NewYork City-based Cantor Seinuk Group to replace an existing 20-story building, the 45-story skyscraper that will serve as the company's new base of operations not only fulfills these requirements; it also stands as one of the 15 tallest buildings in the city.
The structure is 815 ft (248 m) tall and encloses 1.2 million sq ft (114,800 m2) of office space.Yet only 40 percent of this massive building's footprint is situated on natural bedrock; active underground rail lines occupy the other 60 percent. Multiple rail lines passing beneath the building carry passengers into Grand Central Terminal. Tracks run on two levels at depths of up to 50 ft (15 m) below the street. A secondary tunnel system below the tracks houses numerous utility lines as well as major steam lines.
The railroad lines imposed severe logistical and construction constraints: the new supporting structure for the building had to be located between the existing tracks yet could not encroach upon the operating clearances of the railroad. Additionally, the railroad tracks, although temporarily closed off during construction, had to be protected from any damage that might be caused by construction.
To avoid the expense of total demolition and reconstruction, the existing footings that had supported the original building on the site were used to the fullest extent possible. However, to support the increased bulk of the new building, additional footings were added where required. For the most part, rock capable of safely supporting 40 tons/sq ft (3,830 kPa) was located directly below the lower track level, thereby minimizing the footing sizes and the extent of excavation. However, at one major column line, the utilities tunnel-a turn-of-thecentury structure of unreinforced concrete-ran below the lower track.The walls of this tunnel, which still services many of the...