Steel Buildings in Europe

Part 8: Building Envelope 8 - 10 2.5 Structural liner trays Structural liner trays are a popular alternative to composite wall panels. They comprise a deep structural profile into which a slab of insulation is inserted on site. The assembly is completed with the addition of an external profiled metal sheet, as shown in Figure 2.8. Unlike built-up systems, liner trays span directly between the main structural columns, thereby removing the requirement for secondary cladding rails. This is possible because of the depth of the liner tray profile and its resulting bending stiffness. The lack of secondary steelwork therefore can have clear advantages in terms of the speed and cost of the construction process and installation tolerances. However, consideration, should be given to thermal bridging that can exist with liner trays. This issue may be partially overcome by placing an additional layer of rigid insulation on the outside of the tray. Where plastic design of portal frames is a common design approach, the absence of side rails can create issues when attempting to provide restraint to the inside flange of the columns (e.g. in the hogging region of a portal frame), since traditional knee bracing cannot easily be attached to the liner tray profile. Structural liner trays can also be specified with perforations where improved acoustic performance is required. 1 2 3 1 External profile sheeting 2 Insulation 3 Liner tray Figure 2.8 Structural liner tray cladding systems 2.6 Structural deck and membrane roof systems Structural deck and membrane systems provide a long spanning alternative to built-up cladding on cold formed purlins and are especially popular on ‘flat’ or very low pitch roofs on which a waterproof membrane is required. The roof construction comprises a trapezoidal profiled metal deck of sufficient depth and gauge to span directly between the rafters, roof beams or trusses. A common metal deck typically has a profile height of 100 mm and a steel