ABSTRACT
An access scaffold is not a very rigid structure in itself, even if it is braced in the orthodox manner. The reasons for this are:
There is some flexibility in the couplers.
There is some flexibility in the tubes.
There are joints in the tubes.
The centre lines of the members do not come together at node points but are separated by distances of up to 300 mm.
The structures may be very long or very high in relation to their width. For instance, a 16-storey block will have a height to base ratio of about 40 to 1, and a terrace of eight houses will have a length to width ratio of about 40 to 1. Considering the braced frames as lattice beams, they will undergo very high deformation at such high ratios.
Alternate vertical scaffold tube frames are not braced as structural lattices, and the horizontal frames are hardly braced at all.
The consequence of these weaknesses is that the assembled scaffolding would collapse if it did not rely on the building to give it rigidity.