6. Physical Characteristics

Thermal insulation is often required for walls and may be provided by rock wool, glass-wool, chipboard, polystyrene, cellular glass or expanded perlite. Since insulated panels are proprietary products, relevant manufacturer's literature should be consulted as a way of ascertaining specific properties and usage recommendations. Of particular concern are dimensional stability, voluminal mass, heat conductivity coefficient, resistance to compression, resistance to bending, reaction to fire, resistance to water vapour, dew point, ability to act as a heat bridge, and fixing arrangements.

Acoustics

The need for adequate sound insulation is an increasingly stringent requirement for buildings. Absorption and insulation are the two characteristics required for limiting the transmission of noise. It is often possible to combine the dual functions of thermal and acoustic insulation in the one type of composite panel. Particular ways to improve acoustic insulation are to increase the thickness of the profile and/or the density of the insulation or to add an additional sheet between the two skins.

Fire Resistance

Because light gauge sheets are so thin, they do not posses much inherent fire resistance if exposed directly to elevated temperatures. However, properly insulated double-wall cladding can attain a fire resistance of at least 90 minutes. Support roofing and composite flooring may well reach at least 60 minutes without additional protection.

Condensation

A steel wall, especially when not insulated, may be exposed to condensation since its coefficient of thermal conductivity is rather high. However, several anti-condensation coatings have been developed. These coatings are applied to the inside of the wall using an industrial process. They largely prevent subsequent condensation. One such example is Grafo Therm. It is a water-based mixture including porous components with large specific surfaces suitable for absorbing water. It appears in the form of a coating containing very fine granules of a light grey shade which have a pleasing appearance.

Durability

Profiled sheeting is always pre-coated and is obtainable in thicknesses between 0,3 mm and 4 mm and widths of up to 1.500 mm. Galvanising is the normal form of pre-coating. This coating provides cathodic protection to surfaces where the steel is uncoated, e.g. either accidentally or at edges formed by shearing or drilling (Figure 1). A zinc film may be painted on to further improve corrosion resistance, as well as to enhance appearance. Specially produced galvanised and pre-painted systems provide very significant corrosion resistance due to the synergy that exists between the two processes. It is also possible to apply paint to members after roll forming, such as application of polyester powders by the electrostatic process. In all cases, coatings are available in a large range of colours.

Figure 1 Exposure of galvanised sheeting to the atmosphere

Light-Weight Structures Types

Early applications of cold-formed thin-walled steel sections were restricted to situations where weight saving was important. With the advance in the raw material itself and the manufacturing processes, the range of actual and potential use is virtually unlimited.

Light gauge sections are appropriate for use as the steel frame of housing (Figure 2).  Two types are available:

Figure 2 Cold-rolled sections in housing

Two types are available:

• A skeleton completely assembled by bolting on site (Figure 3).
• A skeleton based on the use of steel panels preassembled in the factory.

Figure 3 A steel frame of light gauge sections assembled by bolting on site

Using the second principle, it is possible with quite large panels, e.g. 3 m x 12 m, to introduce a large degree of pre-fabrication into the structure. All sections are pre-galvanised and contain all the holes necessary for wiring, plumbing, etc

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