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SentryGlas® permits non-positive connections in balustrade design

Since 2006, employees and guests at the company headquarters of Seele (Gersthofen, Germany) are witnesses to something fairly unique: a footbridge, leading to offices in the first floor that emits more transparency and lightness than one would usually associate with a construction whose primary purpose is to provide security. Such elegance was made possible by waiving the need for bolt-fixed connections or other positive-fit connecting elements in its 40-meter long glass balustrade. Instead, with the help of SentryGlas® interlayer from DuPont, the bases of the large glass sidewall panes are directly laminated onto plates of stainless steel.
Seele company headquarters, Germany.

As a company specializing in customized structures of steel, aluminum and glass, Seele developed the new technology itself. The international company's own know-how, combined with the excellent mechanical properties of DuPont™ SentryGlas® interlayer, which are maintained over a wide temperature range, were fundamental to the development of the new structure. It relies on the non-positive connection of metal and glass, which is subjected to combined shear and tension loads.

The footbridge at the company's headquarters is a pilot project. The laminate design, which seems to hover weightlessly above the ground, provides daily evidence of its unlimited practicability and is subject to a comprehensive quality assurance program. It is under constant observation as part of strict requirements for its authorization by the building supervisory board.

The laminated safety glass used for the balustrades consists of two sheets of heat strengthened low iron glass and the SentryGlas® interlayer. The individual balustrade sections are 2 meters long, 90 centimeters high, and - to a height of 30 centimeters - they are laminated to the mounting plates with SentryGlas®. In order to achieve this, Seele developed and implemented a special process that ensures the particularly high strength and reliability of the lamination. Seele undertook the entire planning and installation of the project. Manufacture of the footbridge was assigned to Sedak, part of the Seele group.

According to Ingo Stelzer, head of glass production and composites development at Seele: "By incorporating highly transparent SentryGlas® in all of the structurally important connections, we were able to achieve a maximum impression of lightness. Thanks to the interlayer's high strength, shear resistance and good adhesion to glass and metal, as well as the laminating process we developed, the mounting plates reliably and securely transmit loads from the balustrades to the footbridge via a non-positive connection. Our self-supporting glass balustrade is a striking demonstration of what is possible with today's technology."

During manufacture, Seele applied a high-quality grinded surface to the steel plates, before laminating them on to the glass using DuPont SentryGlas®. "Load transfer takes place solely through this adhesion. PVB films are well-suited for facades made of laminated safety glass, yet they would not be able to carry the very high shear and tension loads around, for which this metal-glass connection is designed. The SentryGlas® interlayer is not only more resilient, it maintains its very good mechanical properties at higher temperature ranges," explains Michael Fehlings, European business development manager at DuPont.

"We have full confidence in our pilot project and that it will demonstrate that the new design, with the high-strength interlayer from DuPont, will fulfill all safety requirements and is both neutral in color and reliable in the long term. Numerous requests already reflect the strong interest among the architectural community, who want to create clear, elegant stylistic elements and unusual visual relationships," adds Stelzer.

In the lower section of the self-supporting glass balustrade, installed at the company headquarters of Seele, a SentryGlas® interlayer non-positively transmits loads fromthe safety glass panes to the holding plates.