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Addeddate Identifier et. There are no reviews yet. This was due to the new manufacturing and finishing methods plus an architectural development we now call the Modern Movement. The next major change came with the oil crisis of the s, which forced the building industry into an energy-efficiency rethink concerning the use of glass products [10].
This resulted in systematic research into building physics relationships and led to the development of special functional glasses. The rising cost of energy together with the increasing awareness of the need for sustainable forms of construction without depleting resources have seen the rise of specialised facades since the s.
Their varying, frequently multilayer constructions, sometimes with controllable functional components, are intended to overcome overheating in summer and reduce energy losses in winter. Current research is increasingly concerned with hybrid products in which several tasks are combined directly in one component. In the case of facades, for example, experiments are being carried out on curtain walls with glass photovoltaic panels, which can make an active contribution to energy needs, or passive glass loadbearing panel laminates Figs.
When glass is needed only for the external protective function and transparency is not a requirement, printed or tinted glass is often an option Fig. The development of light-redirecting glass louvres exploits the optical properties of glass. On a constructional level, research is being carried out into combinations of glass and other, in some cases new, ductile materials, e. The aim here is to exploit the respective advantages of each material.
In addition, plastically shaped glass is being increasingly used. The use of suitable adhesives with structural properties — in the automotive industry playing a part in overall stiffness since the s — will also play an ever more significant role in the building industry.
Therefore, progress in science and technology today and in the future will permit the design of pioneering glass projects despite ever more stringent safety requirements. A masterpiece of glass-and-iron construction: the Palm House at the Royal Botanic Gardens in Kew near London GB , , Richard Turner and Decimus Burton Photovoltaic panels in the cavity between the panes of an insulating glass facade left and individually controllable glass louvres for redirecting the light right , Tobias Grau company building, Rellingen D , , BRT Architekten Test panel of a type of dichroic glass for use as a facade element, e.
Glass represents a special case among building materials: its transparency enables a different type of construction, which at the same time dictates a different approach because of the particular behaviour of this material. Like a diva among the building materials, glass reacts immediately and sensitively to improper treatment, which has led to its reputation as an unpredictable material.
But used properly, it possesses inestimable advantages. And the treatment processes are varied and variable. So we have to know and understand glass as a material. It is an amorphous substance produced by melting and rapid cooling, and hence does not have an underlying crystal lattice.
For instance, besides natural glasses, e. Stabilisers in the form of alkaline earth oxides form another constituent; these are added to improve the hardness and chemical resistance of the glass. Finally, quartz glass made from pure quartz sand also belongs to the group of silicate glasses, but plays only a minor role. The transparency is due to the atomic structure, i. The lack of boundary surfaces in the material prevent the reflection of light in the range of visible and longwave UV-A light; the atomic structure cannot absorb this light, which means that light can pass through unhindered.
The glasses used in the building industry are in the main of the soda-lime variety. Besides the principal component, silicon dioxide, there is also a proportion of sodium oxide Na2O , which in the form of soda acts as a flux. Calcium oxide CaO functions as the stabiliser and is dissolved out of the lime that is added to the mix.
In addition, there are further constituents in small amounts that depend on the particular raw materials and the processing conditions Tab. In the case of lead glass, lead oxide PbO replaces the calcium oxide. However, with the exception of glass for protection against x-rays, this type of glass has no significance for the building industry.
Borosilicate glass — frequently used in the building industry, e. The term alkaline earth glasses refers to a group of glass products which again have silicon dioxide as their main constituent but also contain alkaline earth oxides in varying amounts besides calcium oxide.
In these glasses, potassium oxide K2O replaces the sodium oxide. Alkaline earth glasses exhibit a somewhat higher density and a higher modulus of elasticity than soda-lime. The properties of glass Two properties of glass are especially prominent and are firmly tied to this material: its transparency and its fragility.
Comparison of the mechanical behaviour of steel and glass subjected to tension F : whereas steel exhibits plasticity after exceeding the elastic limit and is hence highly ductile f up until the point of failure, glass exhibits a linear elastic behaviour up to the point of failure, without any plastic material behaviour. On the other hand, glass is impermeable to short-wave UV-B and UV-C light because the light energy is sufficient to vibrate the electrons in the glass; this leads to the light being absorbed within the material.
Its fragility and, above all, its sudden failure characterise glass as a typical brittle material. The maximum elongation at failure is in the range of about 0. This means that up until this point the glass behaves in an ideal elastic fashion when subjected to mechanical actions. Plastic material behaviour does not occur, which is why it is impossible to predict failure p. The high proportion of silicate in the composition of the glass is responsible for this behaviour; however, it is the silicate that gives the glass its hardness and strength.
However, when talking about the tensile strength of glass we must distinguish between the theoretical tensile strength the so-called micro-strength of the glass. The former, which can be calculated from atomic and ionic bonds in the glass structure, is very high. In practice, however, sheet glass achieves only a fraction of this theoretical tensile strength. As with all brittle materials, in glass, too, it is the properties of the surface subjected to tension that govern the magnitude of the tensile stresses that can be accommodated.
Surface flaws, notches and cracks — mostly invisible to the naked eye — ensue during manufacture and subsequent treatment and handling. When subjected to loads of any kind, stress peaks occur at these defects and the glass cannot accommodate these by way of plastic deformation, which leads to propagation of the cracks.
And the longer the load is applied, the greater is the reduction in the load-carrying capacity of the glass. So brief peak loads are less of a problem for glass than lower, long-term loads. As the size of the surface area increases, so does the probability of relevant surface damage occurring at a relatively highly loaded point. So as the size of the area loaded in tension also has an influence on the tensile strength and we cannot predict with any accuracy the occurrence, nature and frequency of any surface defects, the tensile strength can only be designated in the form of a characteristic value for the material.
In contrast to this, the compressive strength reaches very high theoretical values in practice, too. As glass is both homogenous and isotropic, these and also all other properties do not depend on direction. Besides their good surface hardness, silicate glasses also exhibit excellent properties with respect to their resistance to chemicals and are therefore ideal where long-term durability is a requirement. Here again, the silicate basis is the reason for the good corrosion resistance.
The majority of acids and alkalis cannot damage glass; one exception, however, is hydrofluoric acid, which is why this acid is used for etching glass surfaces. Glass is also highly resistant to water, but ponding on glass surfaces can lead to leaching in the long-term and hence to corrosion of the glass surface, which manifests itself in the form of cloudy patches.
It is primarily the easy mouldability of glass that makes it suitable for use as a building material. Glass has no defined melting point at which sudden liquefying or the onset of melting occurs, as is the case with crystals.
Glass is characterised by a continual softening as the temperature rises, which means that upon being heated we observe a constant transition from the brittle material via the viscoelastic range to a viscous melt.
It is this property that is exploited for the workability of glass in the form of different production methods plus moulding with the help of heat. Sketch of the principle of the float glass process Sketch of the principle of the rolled glass process Surface textures of patterned glasses selection.
Manufacturing the basic products Sheet glass is the product primarily used for construction applications. All the production methods are preceded by the melting process, the key phase in the manufacture of glass products.
The mixture of raw materials trickles into the input end of the melting tank, onto the surface of the glass bath, and melts there to become glass, which is then removed from the other end as a viscous mass and subsequently formed.
After that the glass can be worked further. Float glass At the start of the 20th century sheet glass was produced by means of a continuous, automated rolling or drawing process that had developed out of the manual methods of the past. When plate glass with a high optical quality was required, the glasses produced by these methods had to be extensively ground and polished afterwards, which was time-consuming and costly.
But the float glass method, which was developed by the British Pilkington company between and and is now the dominant method in glass manufacture, produced glass with an outstanding surface quality without the need for any additional treatment. This produces sheet glass with parallel faces, flat surfaces and completely undistorted transparency. Following cooling, the subsequent working can begin Fig. The glass thicknesses possible with this method lie in the range 0.
The normal conditions during the float process cause a so-called equilibrium thickness of approx. Adjusting the top rollers — serrated wheels resting on the edges of the ribbon of glass at the front end of the float bath — enable the production of thinner and thicker glasses.
These lateral limits enable a thicker ribbon of glass to be formed. The manufacturing process itself results in the two sides of the glass having different chemical compositions. The side in contact with the liquid tin — the bath side — has a higher content of tin ions than the so-called air side. This difference is invisible but can lead to varying behaviour during subsequent processes.
The permissible tensile bending strengths used in design depend on the type of application and must be taken from the relevant code of. Rolled glass This is sometimes called cast glass, a name that stems from the earlier method of manufacture in which the molten glass was poured onto a flat table and subsequently rolled flat. The gap between the two rollers, one above the other, can be adjusted to control the thickness of the ribbon of glass, which can lie between 3 and 15 mm.
After that, the glass is transported on rollers into the annealing lehr before being subsequently cut to size Fig. The standard dimensions available depend on the manufacturer and the specific rolled glass product required. The light permeability of rolled glass is inferior to that of float glass and depends on thickness and surface texture. Rolled glass is used for various products.
Patterned glass, which is available in various designs, is produced by using a textured lower roller Fig. Wired glass, with or without a patterned surface, is manufactured by introducing a wire mesh prior to rolling Fig. Polished wired glass is obtained through subsequent grinding and polishing.
Profiled glass also known as channel glass is also produced from rolled glass. This glass can also be produced with textured surfaces or a wire mesh inlay. As these products can Safety, security The most diverse impact-like loads caused by people or objects can subject glass to stresses and strains in various installation situations in many different ways. Final text received or FDIS registered for formal approval.
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