Structures frame with cantilevering beams

Fig. 35: Frame with cantilevering beams

The I oadbearing structure consists of a series of frames with pairs of columns set back from the facade. As the columns are interrupted by the beams, stiffeners must be fitted between the beam flanges to transfer the vertical loads. The drawing shows three variations for the f loor, all of which share the feature of being positioned above the main beams.

D1 makes use of a secondary construction of small beams or joists placed on top of the main beams. In contrast to secondary beams at the same level as the main beams, this arrangement allows services to be easily routed transverse to the frames. Depending on requirements, the floor itself could be simple wooden floorboards. D2 and D3 do not use any secondary beams or joists and rely on the trapezoidal profile metal sheets to carry the floor - in D2 merely as a support for a dry floor covering, but in D3 as permanent f ormwork for a r einforced concrete slab.

Floor construction D1

Wooden floorboards Steel beams, IPE 160 Total

Floor construction D2

Flooring panels Rubber separating layer Trapezoidal profile metal sheets Total

Floor construction D3

Reinforced concrete topping

"Holorib" sheets

Total

27 mm 160 mm 187 mm

27 mm 20 mm 160 mm 207 mm

120 mm 50 mm 170 mm

Fig. 36: Frame with continuous beams

Shown here with floor constructions above level of primary structure

Fig. 36: Frame with continuous beams

Shown here with floor constructions above level of primary structure

Steel floors

Steel floors consist of profiled metal sheets, 0.801.75 mm thick, with a filling/topping of concrete. The cross-section of the profiling is usually trapezoidal, produced by rolling. Additional ribs and folds are sometimes included to enhance the stiffness. The sheets are available in widths of 0.30-0.90 m. Some forms are known as cellular floor decks.

The sheets can be supplied with or without galvanising (25-30 pm). Non-galvanised sheets are given a coat of paint on the underside to prevent corrosion.

Profiles

1 overview of common profiles 1.1 and 1.2 single profiles 1.3 to 1.7 sheets

1.8 and 1.9 pre-assembled cellular floor decks

Advantages of floors with profiled metal sheeting

- fast erection,

- no formwork required for concrete,

- floors can support loads immediately after erection, anc

- workers below protected against objects falling from above.

Disadvantages of floors with profiled metal sheeting

- steel serves either as permanent formwork only, or

- if required to be loadbearing, the underside needs special fire protection measures, and

- compared with completely dry construction, the I n situ concrete introduces a wet trade into the construction

Form (dimensions in mm)

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