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The weights of the sheets vary from 50-156 N/m2 (see Table 3.3). When the sheets are

installed, side laps and end laps should be provided to make the joint water proof. Thefollowing overlaps are normally used:

(a) For roof: Side overlap –1 ½ to 2 corrugation(b) For side cladding: Side overlap – 1 corrugation

End overlap – 100 mm

ASBESTOS CEMENT SHEETS

Asbestos cement sheets may be used to cover the roof as an alternative to corrugated steel

sheets. These sheets are banned in many countries due to the risk of lung cancer caused

 by inhaling the fibers, while working with these sheets.

SELECTION OF BAY WIDTH

A bay is defined as the space between two adjacent bents (see Fig. 1.42). The roof truss

along with the columns constitutes a bent. The space between two rows of columns of an

industrial building is called an aisle or span. An industrial building may have a singlespan or multiple spans. Figure 14.6 shows industrial building with single, double, and

multiple spans.

STRUCTURAL FRAMING

For the purpose of structural analysis and design, industrial buildings are classified as

(see Fig. 14.6):

•

Braced frames• Unbraced frames

In braced buildings, the trusses rest on columns with hinge type of connections and thestability is provided by bracings in the three mutually perpendicular planes.

These bracings are identified as follows:]

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a) Bracings in the vertical plane in the end bays in the longitudinal direction

[see fig. 14.7 (a)]

  b) Bracing in the horizontal plane at bottom chord level of the roof truss[see Fig.14.7 (c)]

c) Bracing in the plane of upper chords of the roof truss [see Figs14.7 (a) and (b)]

d) Bracings in the vertical plane in the end cross sections usually at the gable ends[see Figs14.7 (a) and (c)]

KNEE BRACING OF COLUMNS

In the braced frames, the roof truss is directly placed over the columns, which

may be an I-section with a bracket or a built-up section. Usually the column is assumed

to the fixed at the base and hinged at the top [see Fig. 14.8 (a)]. This will result in heavy

 bending moments (due to lateral loads) in the columns and hence are adopted when thelateral loads are small and large foundations can be provided.

UNBRACED FRAMES

Unbraced frames in the form of portal frames is the most common form of 

construction for industrial buildings, distinguished by its simplicity, clean lines, and

economy. The frames can provide large column free areas, offering maximumadaptability of the space inside the building. Such large span buildings require less

foundation, and eliminate internal columns, valley gutters, and internal drainage. Portal

frame buildings offer many advantages such as more effective use of steel than in simple beams, easy extension at any time in the future, and ability to support heavy concentrated

loads. The disadvantages include relatively high material unit cost and susceptibility to

differential settlement and temperature stresses. In addition, these frames producehorizontal reaction on the foundation, which may be resisted by providing a long tie

 beam or by designing the foundation for this horizontal reaction.