Like any other part of the structure, cladding is subjected to the same loads – permanent, imposed, wind, snow and ice, and accidental loads.
Cladding panels behave like wall panels and are therefore subjected to the same forces, i.e. axial compression, horizontal flexure due to wind, and in-plane and out-of-plane shear.
But considerations must also be given to loads that may be exerted on the cladding due to either its own or the supporting structure’s expansion during fire. Heat expansion of the cladding panel must be allowed for in the design. Thus:
- Firstly the fixings must be flexible enough to allow for two dimensional movement. As the panel expands, the restraining bolt must have sufficient leeway within the restraining system to move with the panel.
- Secondly there must be a sufficient gap between adjacent panels to accommodate any expansion, otherwise the two panels will meet and be subjected to large compressional stresses.
In the figure below, the gap is too small. Cracks appear as the two panels are push against each other.
