KENTUCKY, USA

Conventional steel framing is used on the lowest four floors of the hotel, but a staggered truss system is used in the upper part of the building, where the full-height trusses make the divisions of the space into hotel rooms. The lower levels have a column grid of 28 x 20 ft (8.53 x 6.10 m) and a framing scheme, which have the main beams spanning the shorter and the secondary beams the longer dimension of this grid. The floor slab is of 4 ½ in (114mm) lightweight concrete acting compositely both with the 3in (76mm) metal deck and the steel beams. Above the fifth level, staggered trusses are used and are spaced at 56ft (17.07m) centres at each floor level, taking the weight of two floors, one each at the top and bottom, and spanning to columns across the complete 60ft (18.29m) width of the building. Pratt type framing of the trusses, with diagonals in tension, is used. However, at the centre of the trusses the diagonals are omitted to allow door openings. The floor here is of prestressed hollow core concrete planks, 8ft (2.44m) wide and 8in (203mm) thick, used without a topping. The shear connection between the floor planks and the top and bottom chords members of the truss is accomplished with shear studs welded to the chords and attached to reinforcing bars projecting from the planks. The voids are then grouted up. The external walls consist of various types of precast concrete cladding units. The internal partitions use gypsum board on metal studs. Where a truss forms the division, it is clad with two layers of gypsum board on each face.

As soon as the trusses were erected, the floor planks were used to stabilise them by welding of a plate embedded in the planks to the chords of the trusses. A typical floor took less than four days to complete.

The staggered truss system is most suitable for narrow shaped buildings which can accept cross walls and is thus of limited application. It is essentially a high rise system, going up to 30 storeys and more, where, as in other high rise methods, as much vertical load is transferred to the outside columns to resist wind forces as is necessary for an economic floor structure. Structural steel used is about 7 lb/ft² (34 kg/m²) of floor area.

Notes:

door n. дверь

economic adj. экономичный

gypsum board гипсокартонный лист

plank n. пластина

staggered truss расположение балочных ферм в шахматном порядке

Ответьте на вопросы к тексту

1. What is the difference between the framing scheme of the lowest floors of the hotel and that of the upper floors?

2. What are the dimensions of the column grid at the lower levels?

3. What kind of concrete are the floor slabs made of?

4. Why are the diagonals at the centre of the trusses omitted?

5. How are the external walls clad?

6. How are the trusses stabilised?

7. Why is the staggered truss system essentially a high rise one?