AN OFFICE BUILDING IN WASHINGTON DC, USA

 

The building contains more than 230 000 sq ft (21 360 sq m) of usable office space as well as parking for more than 250 cars in three basement levels.

At a typical office floor, the maximum spans are approximately 54, 36 and 54 ft (16.46, 10.97 and 16.46 m), these large spans being required both to allow flexibility in the layout of the offices and to give the clear spaces in the basement necessary for efficient circulation in a large car park. The floor area in the basements is slightly larger than that at a typical office level, the floor slab spiralling downward and spanning to the retaining walls instead of the perimeter columns, but the structural arrangement is otherwise similar. Floors from levels 4 to 11 are identical. Prestressed beams at 20 ft 4in (6.20 m) centres are 2 ft x 1 ft 8in (600 x 500 mm) deep, the slab is 5.5in (139 mm) deep and interior columns are 2ft (600 mm) square with external columns 2 ft x 1 ft 6in (600 x 450 mm) in section. The beams are not continuous across the three bays but stopped at third points in the middle bay, which provides both space for horizontal ducts and a convenient position for the anchorages of some of the prestressing strands in the beam. Other prestressing cables in the beam are continuous across the complete width of the building and run in the slab depth over the middle third of the centre bay. The total prestressing force in the two outer bays is typically about 260 tons and that in the centre bay about 160 tons. The stressing of the cables takes place from anchorage points around the perimeter of the floor structure. The floor slab, which spans 20 ft 4in (6.20 m), is also prestressed, at a level of 7.5 tons per ft run.

The building has precast concrete spandrel panels alternating with bands of window and column cladding.

 

Notes:

middle third средняя треть

spiral v. спиралеобразно изгибаться

strand n. арматурная прядь