Glass as structural material
The invention of steel and plate glass in the late nineteenth century made possible an imaginative leap - the transparent steelframed enclosure - which underpinned the development of architecture in the twentieth century. Glass is unique: it is inert yet transparent, but it is also strong, and a new imaginative leap has taken place recently by architects and structural engineers investigating the potential of using glass structurally. They have been faced with the problem of finding design data, which has not been available from a single source; this problem has now been redressed by the Institution of Structural Engineers' new guide, written by Chris Jofeh of Ove Arup & Partners, Structural Use of Glass in Buildings.
Although this is a book primarily for engineers, it is amazing to find, in accessible form, discussions on some of the most exciting buildings in which glass has been central to the concept of the structure. Significantly, in most of them a new technique to serve the concept has been developed by the architects and engineers. For this reason it is also essential reading for any architect interested in glass.
The guide is aimed at two distinct types of users:
those who want straightforward advice on how to use glass with guidance on the applicability of designs or details those who want to design in glass from first principles.
Global code comparisons
What information do structural engineers and architects need to design glass elements which play a structural role in buildings? The glass element may simply resist wind load, or it may carry its own weight, or support live loads of people walking and leaning on it.To the structural engineer the issues ofmost concern will be properties of strength, stability, stiffness, along with durability, robustness and buildability. For those who are relatively unfamiliar with glass structures, the guide compares the structural behaviour of glass with that of other, better known, structural materials.
Structures do not exist in isolation from the buildings they serve; other issues influence structural behaviour or place constraints on what can be achieved.
Non-structural issues, such as the effect of glass on the thermal capacity and acoustic behaviour of the building, the drainage of rainwater and condensation, and methods ofmaintaining and cleaning glass surfaces, may influence design.
Glass can be processed to produce the right combination of qualities to meet a particular need. Float glass can be clear, tinted or coated. It can then be heat-treated, laminated or double-glazed. The guide describes the processes in principle, their implications, and the standards - both American and European - which apply. It does not try to provide up-to-the-minute data on the latest coatings and heat treatments offered by manufacturers, though it lists where this information may be obtained.
The guide is much richer than just an assembly of information; it offers inspiration and practical guidance. The introductory chapters cover principles, design requirements, design selection and calculations. This is followed by a survey of different applications of glass as a structural material in roofs, facades and elsewhere, including the design of glass panels supported on two or more edges, point-supported glass, externally pre-stressed glass and glass in large deflection structures.
Chapters follow on the use of glass as beams and fins, columns and walls, balustrades, stairs, floors and bridges.
The guide is particularly useful in comparing and explaining the codes and standards of different countries. For instance, glass is traditionally supported on one or more edges and many countries have codes of practice for the design of these conditions.These regulations vary, and the guide describes the different limits (for instance of deflection) in various documents, together with a worked example calculating glass using British, American, Australian and Canadian standards to identify their differences and similarities.
All the chapters discuss design and construction with reference to actual buildings many of which first appeared in the pages of the AJ.Performance - strength, deflection and resistance to thermal stress - is dealt with, together with a worked example of a typical structural calculation.
By describing issues that need to be considered when designing structural glass, the different design responsibilities of members of the design team can be clarified (members of the team may well include the glass manufacturer, the glass fabricator and the installer).Useful specification and chapters on the contract are included.
Structural use of glass in buildings. Published December 1999 by The Institution of Structural Engineers, 11 Upper Belrave Street, London SW1X 8BH. ISBN 1 874266 514. Price £55