Concrete addition to Times Sq. transformation.140 West 42nd Street is the first proposed post-tensioned concrete office building in New York New York, state, United States New York, Middle Atlantic state of the United States. It is bordered by Vermont, Massachusetts, Connecticut, and the Atlantic Ocean (E), New Jersey and Pennsylvania (S), Lakes Erie and Ontario and the Canadian province of since the early seventies. The 24-story tower, with a gross square footage approximately 200,000 s/f, includes retail space at street level and typical office space above. Located between two landmark buildings, the Knickerbocker Building and Bush Tower, 140 is an important addition to the ongoing transformation of the Times Square District of Manhattan. Designed by Gruzen Samton Architects of New York City New York City: see New York, city. New York City City (pop., 2000: 8,008,278), southeastern New York, at the mouth of the Hudson River. The largest city in the U.S. , the building's architectural features and function required that office space be shared between the existing Bush Tower and the new proposed space. This requirement meant that the new tower's floor to floor height would have to match Bush Tower's floor to floor height of 13'-9". The architectural challenge required innovative solutions by the structural engineering firm of DeSimone Consulting Engineers of New York City. Also, the floor layout required interior column-free space with all columns located at the perimeter. "After many design iterations which included a composite floor system using W36x (36" deep) steel girders as part of the lateral force resisting system, the design team elected to use a 12" deep post-tensioned banded-beam flat plate as the most economical floor framing system," noted Mike Mota, PE, Regional Structural Engineer for the Eastern U.S. at the Portland Cement portland cement Binding agent of present-day concrete. It is a finely ground powder made by burning and grinding a limestone mixed with clay or shale. Its inventor, Joseph Aspdin (1799–1855), patented the process in 1824, naming the material for its resemblance to the Association. "By using the banded-beam system," added Mota, "a considerable amount of design flexibility was achieved. The post-tensioned "bands" were designed to fit within the 12" slab profile which eliminated the need for floor beams. Beam supported slabs typically increase floor to floor height and add cost and complexity to formwork form·work n. The structure of boards that make up a form for pouring concrete in construction. . As a result, most of the post-tensioning is limited to these "bands" which allows for future retrofitting of the floor slab such as inclusion of slab openings for interior staircases without compromising the structural integrity of the post-tensioning system. The innovative use of the structural design solution in New York City offers unrivaled architectural flexibility with spans reaching almost 40 feet from the curtain to the core and allowed the architects to achieve the same floor to floor height to match the Bush Tower's existing floor to floor height. The alternative composite floor system added approximately 3 feet to each floor which would have made this architectural requirement impossible. According to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. Mota, a key advantage of conventional flat plate systems is the reduction of floor to floor heights which significantly reduces the cost of formwork and building frame. "The flat-plate lends itself to the use of conventional plywood plywood, manufactured board composed of an odd number of thin sheets of wood glued together under pressure with grains of the successive layers at right angles. Laminated wood differs from plywood in that the grains of its sheets are parallel. construction while the lower floor to floor heights allows for the use of conventional stick shoring," said Mota. "Building each floor on a competitive three day cycle, is facilitated by simplified formwork." While an aggressive construction schedule, the two-day cycle is becoming the preferred method of construction in New York City. Unprecedented in office building construction, the two-day cycle will reduce the floor completion schedule by 50% compared to an equivalent structural steel floor system if structural steel changes are required. The lateral force resisting system efficiently incorporated the 12" flatplate with a 16" thick concrete shear wall shear wall In building construction, a rigid vertical diaphragm capable of transferring lateral forces from exterior walls, floors, and roofs to the ground foundation in a direction parallel to their planes. Examples are the reinforced-concrete wall or vertical truss. which completely encases the fire stair stair n. 1. A series or flight of steps; a staircase. Often used in the plural. 2. One of a flight of steps. [Middle English, from Old English from the ground floor. Located at the rear of the property and in keeping with safety and security in post 9-11 construction, all means of egress See ingress. will be protected with 16-inch impact resistant concrete shear walls for occupant occupant n. 1) someone living in a residence or using premises, as a tenant or owner. 2) a person who takes possession of real property or a thing which has no known owner, intending to gain ownership. (See: occupancy) safety. These vertical structural elements Structural elements are used in structural analysis to simplify the structure which is to be analysed. Structural elements can be linear, surfaces or volumes. Linear elements:
Higher strength concrete was specified by the design team to reduce the size of the tower columns and increase rentable space. 12000-psi concrete was used to reduce the column size. |
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