This paper was first proposed by Prof.dr at GPD 2015. Mick Eekhout (General Manager of Octatube Delft and Professor of Product Development at Delft University of Technology).

During my tenure as a professor from 1991 to 2015, I began to research and develop "Zappi", an unbreakable glass structure material. Until 2005, it led to many developments of Fred Veer in my chair. Other research projects have changed the boundaries of possibility, but have not had much impact on practice. To gain a firm foothold in industry and academia, it is possible to enrich both parties through questions, project suggestions and experience. At the same time, in practice, the design, development and construction of the project have truly changed the boundaries.

The "Zappi" bridge of the Chinese Embassy in The Hague; the translucent glass fins of the V&A Museum in London; the Quattro main and triple auxiliary glass fins of The Hague City Museum with long and heavy glass fins; the roof of the Van Gogh Museum in Amsterdam and Extra-long glass fins for external walls; all these projects use glass fins as the main component of the roof and external wall load-bearing structure. Their safety behavior after a board ruptures is also the reason for actual research. Practical loading and destruction tests show that the fracture of 1, 2, or even 3 blades of laminated three-piece fins will not cause collapse and fatal danger.

In 1992, when I started to serve as the Chair and Professor of Product Development at Delft University of Technology, I proposed the idea of ​​developing a new rigid, transparent structural material that is tough, elastic, and resistant to sudden fracture and yielding. In the idea that this is an impossible combination of chemical substances, this pursuit is seen as an impossible ambition, a pursuit of the Holy Grail. The name "Zappi" was introduced as a marketing tool to attract industry and government interest.

Within a year, the staff of Asahi Glass from Japan visited TU and asked us how to use a few staff to develop work that 200 researchers could not complete. It was not until 1995 that Fred Weir served as chairman part-time. He immediately announced that the required attributes were an impossible combination. So after this kind of chemical abortion, there are not many reports in this area. However, in order to innovate the design possibilities of glass engineering, every new idea of ​​architectural design, structural design, and glass design is regarded as a series of unlikely incremental innovations.

For many years, people have been researching, developing and discussing the safety of glass structures. The safety of the glass panel can be generalized. When a single piece of glass is replaced by laminated glass, the safety of the glass panel is over. It is required that a single glass panel is strong enough to resist the manned load of the overhead glass and will not break; stay forever. In situ. Heat strengthened glass is better than full tempered glass.

But the axiom is that the glass plate above the head may break, but it must remain in place at all times, and it should be able to carry the live load of two people: an engineer and a Red Cross. The safety of glass beams is another matter entirely. When the glass beam of the glass fin breaks and collapses, it will cause the consequence of the glass panel to yield. Therefore, the requirement for the glass beam as a trustworthy structural member is to be in place and continue to support the glass panel.

In the Swiss Life / Zwitserleven project in Amstelveen, the Netherlands, the 27-meter-long glass beam is designed from three-layer laminated annealed glass panels, and steel is used at a free height of 25 meters directly above the insurance company’s main entrance. The connectors were knotted together, and the test was broken on a 25 m high glass plate. A fully tempered glass panel was shattered and shattered into pieces, but there were also large fragments that could be fatal when falling from these heights.

A laminated full-tempered glass panel was broken and swept down like an autumn leaf. When it is an exterior wall panel, it will crush some of the lower vertical panels before landing on or on the ground. The lesson learned is that the glass panel must remain in place and everything must be done to prevent it from falling. In the 27-meter-long glass beam designed, breaking from one panel would cause the glass beam to completely collapse.

My initial suggestion was to introduce two suspension cables with a span of 27 m to connect between the glass panels. In that case, the glass beam is not glass, but is not needed by the original designer.

After 3 years of development, the experiment stopped. We invested 90% of the project budget in laboratory work and testing. There was no satisfactory result, and there was no budget to realize the original dream of architects and structural designers. But just before we started testing to load 1 to 2 times the glass beam, the project stopped.

The conclusion of the suspended glass project is: if there is no suitable second load-bearing route, never build a glass beam structure with free span. The metal braided solution is embedded in the double PBB film between the 3 glass panels. Fully tempered glass glass panels and glued connections are possible, but the node test under permitted conditions did not bring us close to the required glass safety The coefficient is 4. Only 8 years later, graduate student Fokke van Gijn solved the problem of high connection force with a patented large glued connector.

This experience is introduced in the contribution of glass fins, because glass fins have the same requirements: the glass fins must never be allowed to yield, because it will cause more glass panels to gradually collapse, which is for users of buildings It is dangerous and fatal. So the requirement for the glass fin is to keep it in place, whether it is broken. It is recommended that the lamination is a three-layer lamination, so that the glass plates on both sides may be broken, while the glass plate in the middle is still effective.

The possibility of producing larger fins through new tempering furnaces and laminating furnaces. The possibility of manufacturing glass structures with glass fins as the main structural beam began in year zero. The first generation was a single solid glass beam in float glass, and later it was fully tempered glass. On the facade, these fins are easily damaged. When the fins initially became larger, they were made of annealed glass. After Seele and NorthGlass initially invested in producing larger fins for Apple stores, the production possibilities increased.

Seele fins are well made, but expensive. NorthGlass fins require an engineer to supervise project production to ensure proper quality. There are also long-distance transportation and transportation issues from overseas in China to Europe, which will take 4 weeks. At the same time, the glass fins are made of three-layer laminate: the glass plates on either side may be damaged and fail, while the central glass plate must still function. In any case, fins of different and larger lengths are possible.

The first major project to use fins of different lengths and angles on the roof was an arch designed for the Victoria and Albert Museum in London. Muma, engineer Tim Mc Farlane, where the insulating and laminated glass plates are forced in a twisted form in the fins. For this reason, the fin adopts a stainless steel top profile, so that the local tension formed on the roof slab will be more evenly distributed on the glass fin. The translucent PVB film in the laminated beam gives the beam an amazing beauty as a wing.

Located at the lobby level of the Dutch Academy of Architecture in Rotterdam, it is arched. Jo Coenen designed and built in 1995 in tension trusses and double-glazed panels, semi-mechanical and semi-chemical Quattro connections. The glass part is the result of a specific funded experiment. The most recent extension was again designed by Jo Coenen's office, designed and realized by Octatube, and replaced the tensile trusses with glass fins. In doing so, the transition from technical care and detail to abstract design is obvious.

The large atrium of 20x40m2 in The Hague City Museum is covered and arched. Job Roos. In 2014, three-layer low-iron glass fins were used as whitish secondary beams to create a perspective effect that opens directly above the audience and closes tangentially (at the end of the atrium). There is a stainless steel connector on the top of these heat sinks, and all silicone glass connects the heat sink and low-iron glass insulating laminated roof panel. The main four-layer laminated glass beam is used in the center of the atrium, which is also low-iron glass, with a span of 13 m and a structural width of 10 m (in the secondary fins), so the glass fins are heavy. Under backlighting, the low-iron main fins are almost invisible.

The design of the roof almost disappeared visually, leaving metal columns and beams as a tribute to the original architect Hendrik Berlage (1856-1934). The side pillars supporting the outer area of ​​the roof and the outer walls are made of low-iron glass fins, so they are almost invisible. They are 200 x 30 mm three-layer laminated glass studs. They make the edges of the roof fly like extended wings.

For the expansion of the Van Gogh Museum in Amsterdam, arched. Kisho Kurokawa, Hans van Heeswijk, 2015, adopted a similar three-layer laminated glass fin, but this time completely transparent, using low-iron glass, spanning the contour of the tubular steel edge, as the bending/compression element of the roof. The specific form of the roof makes it a free-form technology, which leads to the welding of complex shoes on CHS components to connect the roof and the glass fins of the exterior wall. The roof fins are covered by laminated insulating flat and warped glass panels. The outer wall is formed by cold-formed insulated outer wall panels, embraced by electric robots from a flat form to a curved form.

What is the residual strength of a completely broken glass fin? To this end, a test was carried out in the Octatube laboratory. The three-layer fully tempered glass fins used in Gemeentemuseum/Municipal Museum in The Hague are set in a model, and the load is equivalent to the weight of the roof plane (glass panel on the fin) plus the weight of the glass fins live loaded at an interval @ 2m On the roof. The upper details include stainless steel RHS profile, the top of the fin is completely sealed with silicone, and silicone rubber and occasional clips will be placed on the glass panel to prevent bulging.

The first glass plate of the beam was broken without deformation. The second one broke without any deformation. Since a sufficiently tempered character break occurred in the usual small fragments of about 10 mm3, PVB film was purchased together. Afterwards, the middle pane was deliberately destroyed and gradually introduced a small deformation sagging along the length of the glass fin. This complete loading and deformation without yielding lasted 4 weeks. Usually, this period of time is sufficient to connect the bracket and/or replace damaged fins. The support will be the lower steel profile, the upward triangular diagonal and the lateral connection through the upper stainless steel RHS profile between the glass fin and the roof slab.

For me, this is the end of my "Zappi" adventure. It produced a trustworthy glass structure, reliable enough to build roof structures with it. Others may continue to explore, their exploration. A few months before the product development professor retires, I want to announce that my pursuit of Zappi has been completed.

What is the lesson of "The Quest for Zappi"? The pursuit of Zappi is eternal. For me, this is the end of my "Zappi" adventure. It produced a trustworthy glass structure, reliable enough to build roof structures with it. Others may continue to explore, their exploration. A few months before the product development professor retires, I want to announce that my pursuit of Zappi has been completed. Zappi represents an impossible ambition, and every designer should strive for it. It has played a role in my career, and I hope all my engineering colleagues have a similar ambition, their own ambitions. So I will announce:'Zappi found, long live Zappi'. Zabi forever!

The pursuit of Zappi announced in 1992 led to another concept of safety: not at the material level, but at the structural design and detail level. Many experimental projects with progressive innovation have provided safe glass structures for overhead glass, whether in glass planes or in glass beams using glass fins. Extreme load testing in the Octatube laboratory produced a reliable glass fin structure.

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