Remo
Pedreschi
Professor of Architectural technology, University of Edinburgh, Architecture, r.pedreschi@ed.ac.uk
Natural stone is a material of great character and architectural beauty. Its roots lie in traditional craft based construction, in mass, load-bearing structures. However as framed buildings evolved in the 19th century it became used less for its physical qualities and more for its visual and symbolic attributes, as a skin to cover and protect the frame. The separation of the load-bearing function from the enclosing function of the wall enabled taller and lighter buildings to be constructed at faster rates. Various methods of attaching the stone to the frame have developed that rely on different levels of traditional stone masonry skills. The most common methods of attachment of stone to structural frames are:
Professor of Architectural technology, University of Edinburgh, Architecture, r.pedreschi@ed.ac.uk
Natural stone is a material of great character and architectural beauty. Its roots lie in traditional craft based construction, in mass, load-bearing structures. However as framed buildings evolved in the 19th century it became used less for its physical qualities and more for its visual and symbolic attributes, as a skin to cover and protect the frame. The separation of the load-bearing function from the enclosing function of the wall enabled taller and lighter buildings to be constructed at faster rates. Various methods of attaching the stone to the frame have developed that rely on different levels of traditional stone masonry skills. The most common methods of attachment of stone to structural frames are:
- to use a secondary
arrangement of stainless steel supports attached to a backup wall onto which
the stone is hand-set using traditional stone masonry techniques and pointed
using conventional mortars
- to construct pre-cast
concrete cladding panels with stone facings (25 - 40 mm in thickness) mechanically
attached during casting to a concrete panel
- Thin stone panels in an
open jointed rain-screen, supported on a secondary framing system attached either
to a back up wall or to secondary steel frame.
These systems are covered by
relevant British Standards.
The construction industry is facing increasing demands to industrialise the fabrication and assembly processes, reduce material consumption and improve efficiency although current systems have some disadvantages. Stone compared with other cladding materials is relatively expensive and hence the use of stone is sensitive to these pressures. In all these approaches the stone is simply the outer layer of a multi-layer façade. The use of hand set stones is slow and requires extensive scaffolding. The construction of a rain-screen façade requires considerable engineering design of the support framework and the use of pre-cast concrete adds additional weight to the structure. In all the systems the intrinsic compressive strength of the stone is not used, the primary structural action on the stone is flexure. An alternative construction is to use post-tensioning to create prefabricated stone cladding panels. These panels take advantage of the compressive strength of the stone and can eliminate either the secondary steel work and subsequent site operations or the need for pre-cast concrete panels, reducing both the overall weight of the panels and eliminating the need for formwork and concrete.
The paper presents a feasibility study into the construction and behaviour of post-tensioned stone panels. It was part of a larger project into the development of industrialised methods of stone cladding. An initial study was carried out on a simple panel to assess the proposed method of pre-tensioning. This was followed by a construction study to investigate the design and manufacture and installation of a full-scale panel without mortar. The final study was a series of structural tests on four panels of varying thickness and stone type to investigate the flexural behaviour and construction sensitivity.
References
BSI, BS 8298 part 3 Code of Practice for the design and installation of natural stone cladding and lining, The British Standards Institution, 2010, London.
The construction industry is facing increasing demands to industrialise the fabrication and assembly processes, reduce material consumption and improve efficiency although current systems have some disadvantages. Stone compared with other cladding materials is relatively expensive and hence the use of stone is sensitive to these pressures. In all these approaches the stone is simply the outer layer of a multi-layer façade. The use of hand set stones is slow and requires extensive scaffolding. The construction of a rain-screen façade requires considerable engineering design of the support framework and the use of pre-cast concrete adds additional weight to the structure. In all the systems the intrinsic compressive strength of the stone is not used, the primary structural action on the stone is flexure. An alternative construction is to use post-tensioning to create prefabricated stone cladding panels. These panels take advantage of the compressive strength of the stone and can eliminate either the secondary steel work and subsequent site operations or the need for pre-cast concrete panels, reducing both the overall weight of the panels and eliminating the need for formwork and concrete.
The paper presents a feasibility study into the construction and behaviour of post-tensioned stone panels. It was part of a larger project into the development of industrialised methods of stone cladding. An initial study was carried out on a simple panel to assess the proposed method of pre-tensioning. This was followed by a construction study to investigate the design and manufacture and installation of a full-scale panel without mortar. The final study was a series of structural tests on four panels of varying thickness and stone type to investigate the flexural behaviour and construction sensitivity.
References
BSI, BS 8298 part 3 Code of Practice for the design and installation of natural stone cladding and lining, The British Standards Institution, 2010, London.
Curtin, W. G., The
Investigation of the Structural Behaviour of Post-tensioned Brick Diaphragm
Walls, The Structural Engineer, 64B(4), 1986, London, pp. 77–84.
Pedreschi, R. F., and Sinha,
B. P., Deformation and cracking of post-tensioned brickwork beams, The Structural
Engineer, 63, (16), 1985, London,
pp. 93–99.
Pedreschi, R.F., Eladio
Dieste, The Engineer’s Contribution to Contemporary Architecture, Thomas
Telford Publishing, 2000, London.
Werran, G. R. and Dickson.
M. G. T., Pre-stressed Ketton Stone Perimeter Frame: The Queens Building, Emmanuel
College, Cambridge, ICBEST ’97, Centre for Window and Cladding
Technology University of Bath, 1997, Bath, pp235-240.
Donaldson, B. (ed), New
Stone Technology, American Society for Testing and Materials STP 996, ASTM, 1988,
Philadelphia.
Brown, A., Peter Rice,
The Engineer’s Contribution to Contemporary Architecture, Thomas Telford Publishing,
2001, London.
Dernie, D., New Stone
Architecture, Laurence King Publishing Ltd, 2003, London.
Kawaguchi, M., Steel: The Leading Player for Enhanced
Large-span Hybrid Structures, Steel Construction Today and Tomorrow, The
Japan Iron and Steel Federation, No.34, November, 2011,Tokyo, pp. 1-3.
BSI 2006a, BS EN 1926:
Natural stone test methods - Determination of uniaxial compressive strength,
The British Standards Institution, 2006, London.
BRE, The BRE Stone List, http://projects.bre.co.uk/ConDiv/stonelist/index.html,
The Building Research Establishment, Watford,
accessed 24/07/2012
BSI 2006b, BS EN 12372:
Natural stone test methods - Determination of flexural strength under concentrated
load, The British Standards Institution, 2006, London
Hendry, A.W., Structural
Masonry, Palgrave MacMillan, 1998, Basingstoke
García, D., San-José,
J.T.,Garmendia L. and Larrinaga, P., Comparison between experimental values and
standards on natural stone masonry mechanical properties, Construction and
Building Materials, Vol.28, 2012, Oxford, pp. 444-449.
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