A feasibility study of post-tensioned stone for cladding

As contemporary building technology evolves to meet the challenges of increasing industrialisation and prefabrication of the construction process the demand for more efficiency also increases. Stone is a material of great architectural character and expression. It is used extensively in Scotland, in traditional building but now mostly in corporate or institutional buildings and indeed it helps define the character of many Scottish cities. It is however, not immune to the pressures for efficiency. Working in collaboration with a stone contractor a feasibility study was undertaken to examine ways to use stone more efficiently by reducing the quantity of stone and simplifying the installation process. This paper presents the preliminary results of a study into the structural behaviour and design of post-tensioned stone panels, intended as cladding for buildings. In contemporary applications stone is attached to buildings in a variety of ways, connecting to the supporting structure using steel angles and brackets or by incorporating the stone in a pre-cast concrete panel. By post-tensioning the stone, prefabricated panels can be made which eliminate either the secondary steelwork and subsequent site operations or avoid the need for pre-cast concrete panels. A series of full-scale post-tensioned beams using different thicknesses and types of stone were tested. The degree of pre-stress, the load–deflection response and serviceability of the beams is reported. Further studies were also carried out on full-scale prototype panels used to consider the construction process, anchorage details and methods of attachment to the primary structure. The results show that simple techniques for post-tensioning stone can be developed that reduce the need for highly skilled labour and can result in efficient construction processes. The results can be applied to a broad range of load bearing stone elements such as columns, beams and vaults.

► A study of the feasibility of a novel of form post-tensioned stone cladding.
► Full-scale construction prototypes using a completely dry method of construction.
► Construction simulates conventional stone cladding but much more rapid.
► Structural testing of post-tensioned panels demonstrates that low levels of pre-stress required.
► Panels exhibited high rates of recovery when loaded past decompression of pre-stress.