The performance and optimal use of metal cladding is affected by the different types of load it is subjected to during the course of its lifetime. These loads can be broadly categorised as point load and uniformly distributed load (UDL).
Modes of failure and fastener loads are discussed in other clauses under the main clause 3 Structure.
The performance of profiled metal cladding under load depends on its ability to resist the tension (stretching), compression (squashing), and shear (sliding) forces that it is likely to be subjected to during the lifetime of the building.
When a beam is subjected to bending, one flange will be under compression and the other under tension.
Loads acting on roof cladding are generally classified into two types: point load and uniformly distributed load (UDL). A point load is applied to a particular area, but a UDL impacts on the total area of the roof.
Optimum performance of roof cladding under load depends on the continuity over several spans.
An adjacent continuous span assists the performance of profiled metal cladding, as continuity can reduce deflection up to 50%. In single spans the cladding is free to rotate at each support, but with continuity at a support the cladding is held down by an adjacent span; reducing the rotation and deflection.
The end span of profiled metal cladding should be no more than two-thirds of the intermediate span for optimum performance under both point load.
Load distribution greatly affects the deflection. A load distributed equally along the length of a beam (line load) will cause less deflection than the same load being applied to the centre of the beam.
The depth of the profile of metal cladding is another important criterion in the design and use of metal roof and wall cladding. Given the same cross section area, the deflection of the profile will vary with the square of the depth, with the trade-off of higher buckling modes.
