Урок 4.12

Текст A

XEROX CENTER, CHICAGO, ILLINOIS, USA

This office block has 40 storeys and a gross floor area of 880 000 sq ft (81 750 sq m).

Except at the rounded corner, the column grid in both the east-west and north-south directions is 22 ft 6in (6.86 m) in each end bay and 20 ft (6.10 m) in the intermediate bays. An 8in (200 mm) thick reinforced concrete flat slab spans between the columns at each floor level. However there is a 2 ft (0.60 m) deep beam connecting the perimeter columns and at the top of all the interior columns. Interior columns are square and perimeter columns are circular, both increasing in size down the building. At street level the interior columns are 3 x 3 ft (0.91 x 0.91 m) and are made with 6000 psi (42 newtons per sq mm) strength concrete. Lateral stability is provided by core walls which increase in thickness down the building and interact with the perimeter frames. The core walls are all about one foot thick at mid-height.

The feature of this design is the enclosure. There are horizontal bands of double glazing, of green colour from the outside, alternating with insulated aluminium panels coated with a fluoropolymer which is white. Transom and mullion pieces are in the same aluminium. The cladding all comes as pre-assembled panels 5 ft (1.52 m) wide by 11 ft (3.53 m) high. The horizontal joint between each panel is put above the glazing. The wind pressure on the cladding at the top of the building, where it is not protected by the surrounding buildings, is expected to reach up to 60 lb/ft² (294 kg/m²). Each column is founded on a caisson and the core walls - on a series of caissons. The caissons have a diameter of 4 ft 6in (1.37 m) and extend some 50 or 70 ft (15 or 20 m) to the bedrock.

The flat slab floor has relatively small depth allowing room for horizontal service runs, the principal reinforcement being provided along column lines. Because the slab is relatively flexible, compared to the perimeter beam, that part of the lateral load not taken by the core structure is taken by the perimeter frames rather than the internal construction. The action of the perimeter frame is most effective near the top of the building.

The total construction time was 24 months. The floor slab at each level took approximately one week to complete. Two tower cranes, taken through the north and south parts of the building, were used.

Notes:

deep beam балка-стенка

fluoropolymer n. фторсодержащий полимер

rounded adj. закруглённый

tower crane башенный кран