This type of panel consists of 3-6 mm sheet metal formed into a metal pan on the outside face, either by cutting and welding the metal into a tray or; more usually, by spot-welding angles that form the edge to the tray.The stiffness of the panel thus depends upon the thickness of the metal and the number of stiffening angles (Fig. 6.24).
The panel is supported by a fixing rail or some form of secondary framing, and the insulation is
normally applied loosely on site, although In some cases It can be glued to the back of the panel In the factory. The Inside face is finished either with another metal sheet or with a conventional interior finish material such as gypsum plasterboard. The essential difference between this type of panel and the other types described is that the insulation and inner linings do not add to the total stiffness of the panel. One problem in manufacturing such panels is that of avoiding the rippling of the surface or 'oil canning effect' and ensuring that the sheet metal is perfectly flat and smooth, which also influences the thickness of the metal used.
In order to allow for thermal expansion of the aluminium rolled sheet, it is now advised that the sheet is not directly connected to the angel framing, but 'floated' onto its supports using Z-section cleats (Fig. 6.25).These cleats are spot-welded to the sheet during fabrication, thus holding it within the frame. Following fabrication, the edges are sealed with a silicone joint. Pins can also be used welded to the back of the sheet onto which the sheets of insulation are mounted.
Many projects in the USA have been constructed using rolled sheet panels. These would include the City-Corp Building in New York (curtain walling by Flour City) and the Richard J. Hughes Justice Complex at Trenton, NJ (architects: the Hillier Group, Princeton), also supplied and erected by Flour City. Such panels were also used at the Federal Reserve Bank building in Boston (architect: Hugh Stubbins), where flanges were welded onto 5 mm plate aluminium, and the Bronx Centre, New York (architect: Richard Meier), where 3 mm aluminium sheet was brake pressed and the corners formed by cutting and welding into a tray. These were mounted onto a secondary framing on site, with insulation and inner linings applied in situ. For a detailed description of these projects, see Murphy (1978).
The maximum size of rolled sheet panels tends to relate to the size of sheets available (normally 1.5 mm width maximum), and the weight of units when assembled. Panels at the Bronx Centre, which were mainly 3.45 m wide x 0.75 m, 1.5 m and 1.35 m high,
Rolled sheet • spot welded to Z-cleat
Pin welded on to receive insulation k
6.25 Alternative methods of fixing angle framing to rolled steel panels: (a) Z-section cleat spot-welded to sheet; (b) welded stud on outer sheet with slotted holes in angle framing.
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