Glass with a load-bearing function
As the building in Paris shows, glass has its own load-bearing qualities and can therefore be used for precisely such purposes in structural engineering. This means that flat glass is suitable as a primary, not just secondary material. There are no irritating braces and no metallic reflections – just pure glass.
Furthermore, the load-bearing effect of the glass can be reinforced – another feature that is illustrated by the Louis Vuitton Foundation. This makes it possible to enhance not only the normal load-bearing capacity of the glass, but also its residual load-bearing capacity after potential breakage. If an appropriate and structurally efficient film is used, manufacturers can now produce a laminated glass that will carry the weight of a person after breakage, despite a nearly 30% reduction in thickness.
In the future the load-bearing properties – the shear modulus – of such a film will assume an even more important role in the structural analysis of components for construction purposes. The coefficient provides information about the linear elasticity, created for instance by a shearing force.

Structural glass engineering stands or falls by the mounting option that is applied to the material on the support structure. Prof. Ulrich Knaack from the Technical University of Darmstadt and Delft University of Technology sums it up as follows: “Façade engineering is high-end technology at a building site.”
The most common type of glazing involves linear mounting. The main components of this option are horizontal and vertical exterior mullion-and-transom designs with interior pressure bars and elastic supports, e.g. made from silicon. The result is a sleek silhouette.
 
The spot-fitted bracket has stainless-steel retaining bolts which hold the glass pane in place and eliminate the need for sections. To do so, the glass needs to be drilled through, creating some highly concentrated tension at the drillhole. This is why conventional spot fittings only permit the use of prestressed glass (i.e. tempered safety glass or partially toughened glass).
 
Apart from the option of drilling through the panes, a rear-ventilated façade also allows the use of clamping mounts on edges and joints, holding the pane in place.
 
A so-called undercut anchor fulfils the same functions as a drilled-through spot-fitted bolt. Yet the drill hole is conical in shape, and not a through hole. On the outside of the glass façade this results in a completely smooth surface, which is easier to clean.

Positive side-effects of structural glass engineering
During the last few years developments in façade construction have led to and changed a number of further products which are not directly related to façades. For example, balustrades with load-bearing properties are now becoming increasingly popular. They can be found on observation decks, in rooftop restaurants and in smart penthouse apartments – places where it is important have an unobstructed view, while also offering safety. As well as expanding the architect’s freedom of design, glass has numerous further benefits in construction – advantages which are not just visual. Pre-shaped, sectioned glass elements can be delivered to a building site in a customised form and can be used just as they are. Approved and prefabricated glass construction elements for glossy glass railings can be clicked into the supporting structure on site where they can be variably adjusted, so that they are ready for use straightaway. This saves valuable time in the planning of large construction projects – and very often also money.
The architects and engineers do, however, need exact specifications and thorough calculations, so that they can meet the strict DIN and EN requirements that are stipulated by law to ensure safety and structural stability. They also need glass manufacturers and finishers with state-of-the-art machinery – a segment where Germany’s glass industry is in a good position. SMEs are making the most of these opportunities and are increasingly concentrating on sophisticated niche products.

“Structural glazing light” for private customers
Although today’s bonded glass panes in private housing do not qualify as genuine structural glass engineering products, they are nevertheless a technically inspired side effect of this discipline. There is now a growing demand for slim sections in bonded windows, and indeed not just for conservatories and patio canopies. What makes them attractive is that they require fewer load-bearing elements and visual irritations. After all, builders of private houses, too, want to benefit from this forward-looking engineering in their construction projects. Even in existing properties window areas are now being enlarged, panes are inserted down to floor level, and box frames in timber-framed houses are filled with glass.
“There’s a clear trend towards higher quality in refurbishment and new builds than there was a few years ago,” said Martin Langen from B+L Marktdaten at a conference held two years ago by GKPF, the German Quality Assurance Association for Plastic Window Systems1). Thanks to outstanding thermal properties and tight sections, it is possible to create a large amount of space for windows within the brickwork.
 
The market has responded with some remarkable products. Large windows and sliding doors can be divided with the help of a classic mullion-and-transom design at a visible frame width of 50 mm. An even leaner option is offered by GIP Glazing, with a width of only 15 mm, while still reaching a heat coefficient of 0.90 W/(m2K).
 

glasstec 2016 in Düsseldorf in September will showcase today’s global state of the art in structural glass engineering, delivering important stimuli for the global glass industry. The two highlights will be a special show entitled glass technology live, with presentations at an accompanying symposium, and a new conference, Function Meets Glass, on 19 and 20 September 2016.
www.glasstec.de