Historically, flat glass production was a handcrafted process, resulting in glass elements with optical imperfections that altered the clarity of the view through windows – this is a decisive aesthetic feature today. In contrast, modern glass used in building industry is predominantly produced through the float glass process. Since its development in the 1960s, it enabled the mass production of fully transparent glass free of irregularities. Thereby, traditional flat glass production methods, such as the cylinder-blowing or rolled-glass processes, were displaced to both economic and quality improvements. However, with the discontinuation of older methods, the authenticity of historical buildings was also diminished. To preserve authenticity, contemporary projects aim to incorporate glass produced using traditional techniques, embracing the inherent optical irregularities of handcrafted glass. One challenge is that mouth-blown glass lacks standardization in terms of product specifications, with no established values for geometric tolerances or strength. The primary objective of the presented research is to characterize the load-bearing capacity of contemporary produced mouth-blown glass in comparison with float glass which will lead to a method for determination of strength in the future. Additionally, the study explores the effects of thermal treatment of mouth-blown glass. The research involves geometrical and photoelastic analysis of 63 samples of mouth-blown glass with 2 mm thickness. Afterwards, the four-point-bending-test (EN 1288-3 (2020)) is adapted to test samples to fracture, to evaluate the load-bearing capacity and fracture pattern. The samples were produced in 2024 using the traditional cylinder-blowing method . The results of the study confirm and quantify significant thickness tolerances in mouth-blown glass. But the results also demonstrate considerable potentials for the use of mouth-blown glass in the building industry. The load-bearing capacity of modern mouth-blown glass was found to be comparable to modern annealed glass. Thermally toughening did not reach strength levels of fully tempered float glass. The paper also discusses the importance of considering thickness tolerances when estimating realistic glass strength values.

The bending strength of flat glass panels including the effects of their edges, is commonly determined by means of the four-point bending test method. This is an established and reliable method. However, when testing glass thinner than 3 mm, large deformation may occur. This means that the calculated stresses might not correspond to the actual, as the hypothesis behind the small deformation theory does no longer hold. Furthermore, it might occur that the specimen slips out of the supports, compelling the testing impossible. An alternative method, suitable for thin glass, consists of inducing an increasing curvature from flat until fracture. The curvature is to be constant along the length of the specimen at any time. The stress at fracture is calculated by knowing the corresponding radius or the applied bending moment. The equipment capable of performing this test is the clamp bender whereby the glass is held by two clamps at the specimen's ends. Rotational and translational movement combine to uniaxially bend the glass as desired. This paper explores the validity of the clamp bender for testing thin glass by comparing the results generated by three different test setups developed at TU Darmstadt, TU Dresden and AGC. The three individually developed clamp bender setups follow the same principle, but present a few differences in actuation. Using these three clamp bender test setups, identical series of thin glass specimens were tested. The results showed that the glass fracture strength data coming from different setups match quite well one another. This paper discusses the different test setups and compares the obtained glass strength data. It contributes to the development of a universally applicable, simple and reliable test method for thin glass.

The development of space grid structures experienced its maximum momentum in the third quarter of the last century. The mathematical and structural principles were described and many thousands of steel space grid structures in different shapes built. An advancement of form and structure of double layer space grids therefore cannot occur in the structural principle but in the use of new materials replacing parts of the structure. Today in 2016 the authors are pleased to announce that more than five years ago a space grid structure with an upper (compression) layer made of glass panes only, perfectly fulfils its task covering a courtyard in the German capital Berlin. At this structure, on the basis of a traditional steel double layer grid all members in the compression layer are replaced by the glazing. The glazing fulfils a double function. It serves either as the primary load bearing system and transfers significant in-plane loads or as roof covering. The panes are connected by steel knots at their corners and transfer in-plane forces via adjustable contact blocks. After the main research phase the first commercial project using this new concept was launched in 2007. With a dimension of 15 m x 21 m and an arch rise of 3.50 m it covers the courtyard of one of the Berlin palaces. In autumn 2009 the palace was going to be re-opened to the public. The design process was attended with extensive testing to obtain an individual approval. This contribution describes the testing at single panes and at a full-scale arch of 15 m span. Plastics for the in-plane load application into the glass edge and their creeping behaviour were investigated in first tests. The stability behaviour against glass pane buckling was tested at relevant load combinations and the post breakage robustness and the walk-on ability of the overhead glazing ensured by suitable test. Load bearing tests with a total load of 13 tons were applied on one 15 m arch and finished the test series. Within the last years the structure and its components were monitored. With these experiences valuable feedback to the testing and design steps and recommendations for further projects were gathered.

From the perspective of standardization of glass in building, the year 2015 marks a significant break with the official introduction of DIN 18008 part 1-5. The technical guidelines TRxV are a thing of the past. Additionally, the draft of DIN 18008-6 standardizes remaining security-related glass structures by defining additional provisions for accessible glass. The standard includes an impact calculation according to DIN 180084. There is small experience with dynamic calculations in glass available today. Therefore, potential users raise reservations about this method resulting in a lack of confidence. This paper shows a full example to break down those reservations. It is expressly stated that a dynamic calculation causes favourable results.

The article describes material tests on plastics for the use in high mechanical loaded blockings. With a selection of ten potential capable thermoplastics the material properties for short time load under tension and compression by several temperatures and for long time load will be compared. On the basis of this material tests a recommendation for the use of this thermoplastics in high loaded blockings and a limitation of use will be given.

The Technische Universität Dresden, Germany was decisively involved in the development of a glazed roof structure. Especially the activation of the in-plane load transfer – a structurally membrane behaviour – of the all-glass roof was main objective of the research. After the realisation of a few prototypes and a finished project within the last years, the research focus changed to the load application of in-plane forces into the glass edge. A powerful material for the load application into the glass edge is the necessary condition for the construction of membrane glass roofs. This contribution comprehensively describes relevant contact materials for glass constructions. The broad range of plastics is investigated on their ability to transfer large compressive stresses into the glass edge. The visco-elastic material behaviour under compressive stress is described by testing data and spring-damper-elements. Long term testing of the plastics under compression deliver relevant information about the material behaviour in glass roofs over the structural lifetime. Cyclic testing allows determining the percentage of elastic, the visco-elastic and the viscous strain. By means of appropriate solid plastics the construction of an absolutely new glass roof with membrane structural behaviour was realised and demonstrates the practical relevance of the presented research.

Within the last years the Institute of Building Construction, Technische Universität Dresden, has been decisively involved in the development of transparent space grid structures. These structures base on steel space structures, at which all steel members in the compression layer are replaced by in-plane load bearing glass panes. In 2009, the first glass roof of this new construction type was erected above the inner courtyard of the Berlin palace Reichstagspräsidentenpalais. The roof consists of a single curved, double layer transparent space grid structure with dimensions of 14 m x 21 m. The load transfer in the compression layer is ensured by insulating glass units with regular dimensions of 1.80 m x 1.26 m. This contribution describes the concept, the structural design, the testing and the erection of the first transparent space grid roof with load bearing structural glass.

AbstractDas Institut für Baukonstruktion, Technische Universität Dresden, ist maßgeblich an der Entwicklung von selbsttragenden transparenten Raumstabwerken beteiligt. Diese basieren auf stählernen Raumfachwerken, bei denen alle Stäbe der Druckebene durch in ihrer Ebene lastabtragende Verglasungen ersetzt werden. Im Jahr 2009 wurde eine erste Dachkonstruktion dieser neuartigen Bauweise über dem Innenhof des ehemaligen Berliner Reichstagspräsidentenpalais errichtet. Dabei handelt es sich um ein zweilagiges, einachsig gekrümmtes, biegesteifes Raumtragwerk mit Abmessungen von 21 m x 14 m. Der Lastabtrag der Druckkräfte in der Obergurtebene wird durch Mehrscheiben‐Isolierglas mit Scheibenabmessungen von 1,80 m x 1,26 m sichergestellt. Dieser Beitrag beschreibt das Konzept, die Tragwerksplanung, die Bauteilversuche zur Erlangung der ZiE sowie die Bauausführung.Transparent space grid structure above the inner courtyard of the Berlin palace Reichstagspräsidentenpalais. The Institute of Building Construction, Technische Universität Dresden, is decisively involved in the development of transparent space grid structures. These structures base on steel space grid structures, at which all steel members in the compression layer are replaced by in‐plane loaded glazing. In 2009, the first glass roof made of this new construction type was erected above the inner courtyard of the Berlin palace Reichstagspräsidentenpalais. The roof consists of a single curved, double layer transparent space grid structure with dimensions of 21 m x 14 m. The load transfer in the compression layer is ensured by IGU with regular dimensions of 1.80 m x 1.26 m. The contribution describes the concept, the structural design, the testing and the erection.

The TU Dresden is decisively involved in the development of a sustainable and transparent glazed roof structure. The designed transparent space grid structure is based on a conventional steel space grid, in which all steel members of the compression layer are replaced by glass panes. The glazing transfers large in-plane forces and serves as roof covering.Two full-scale mock-ups of a double layer space grid structure in the structure geometries half- octahedron plus tetrahedron and half-Vierendeel demonstrated the feasibility to build such new structures.To achieve an individual approval comprehensive testing was conducted. This included small sized testing of block elements for the local load application into the glass edge, in-plane stability tests, walk-on and post breakage behaviour tests and load bearing tests at roof strips of about 15 m length. In the structural tests the glazing had to resist a load with the safety factor of 3.0.

Space grid structures are appropriate to cover large areas. They allow the realization of plain roofs. To improve the transparency of such structures a new type of sustainable und transparent double layer grids is developed. The strict replacement of all bars in the compression layer by glass panes significantly increases the transparency and saves material. The contribution describes the geometry finding for such structures. Basis for the research is the structure geometry of steel space grid structure that is extended to transparent space grids. As result of the research a full-scale mock-up of the most appropriate structure was built to demonstrate the feasibility.

The TU Dresden is decisively involved in the development of a sustainable and transparent glazed roof structure. The designed transparent space grid structure is based on a conventional steel space grid, in which all steel members of the compression layer are replaced by glass panes. The glazing transfers large in-plane forces and serves as roof covering. Prerequisite for these structures is the load application of significant compression forces into brittle glass edges. Until now, no comprehensive scientific research has been carried out to investigate suitable contact materials for axial load application at glass edges. The intended detail design requires a contact material, which is softer than glass while providing a high compressive strength, low creeping and a working temperature range between -20°C and +80°C. A large number of metal alloys and polymers were tested with regard to their compressive strength. Tests on their creeping behavior started in 2008.The results of current investigation were applied to optimize a full-size roof mock-up, spanning over a distance of 15m.

Das Institut für Baukonstruktion, Technische Universität Dresden, ist maßgeblich an der Entwicklung von selbsttragenden, transparenten Glasdachkonstruktionen beteiligt. Der vorliegende Beitrag beschreibt das Grundprinzip einer solchen materialeffizienten Struktur. Ausgehend von zweilagigen Stahlraumfachwerken werden geeignete Geometrien identifiziert, die es erlauben, alle Stäbe der Druckebene durch in ihrer Ebene lastabtragende Verglasung zu ersetzen. Die Kraftweiterleitung der Glasscheiben geschieht durch in den Ecken angeordnete Knotenpunkte. Neben statischen Berechnungen wurden an kleineren Prüfkörpern als auch an Versuchsfeldern von bis zu 15 m Länge umfangreiche Versuche durchgeführt, die Schwerpunkt des Beitrages sind. Sie umfassen die Lasteinleitung, das Stabilitätsverhalten der Scheiben, die Tragfähigkeit des Gesamtsystems als auch die Betretbarkeit und Resttragfähigkeit.

At the IASS conferences in 2007 [1] and 2008 the concept and testing results of a sustainable and transparent roof construction were presented. These transparent space grid structures base on a double layer grid in which all bars in the upper layer, the compression layer, are replaced by glass panes. The glazing is part of the primary load bearing system and transfers significant in-plane forces. In 2007 the first realisation project using this new concept was launched and will be finished this year. With a dimension of 13.5 m x 21 m and an arch rise of 3.50 m it covers the courtyard of one of the Berlin palaces. The design process was attended with extensive testing to obtain an individual approval. This contribution describes the testing at single panes and the full-scale arch of 13.5 m span necessary for the individual approval of the building authorities. Plastics for the in-plane load application into the glass edge and their creeping behaviour were investigated in first tests. The stability behaviour against glass pane buckling was tested at relevant load combinations and the post breakage robustness and the walk-on ability of the overhead glazing ensured by suitable test. Load bearing tests with a total load of 13 tons were conducted at one 13.5 m arch and finished the test series. The successfully finished testing is the basis for the individual approval and the realisation of the roof construction within the next month.

The development of transparent space grid roofs made of steel glass modules can be described by the systematic replacement of elements in the compression layer of a steel space structure by glass panes. In this structural system the glazing serves either as part of the load bearing system or as roof covering. The use of the material glass requires the execution of extensive experimental tests. This article describes testing on the global structure to verify the function of the glass pane with regard to its axial load transfer. All described testing was done at a full-scale mock-up with 10 m span.

Many transparent roof structures have been built worldwide in the last decades. These transparent structures have usually curvilinear forms. This geometry allows the activation of membrane forces and thus very slender steel profiles of the structural system. Plain structures usually work as bending systems and are mostly less transparent steel structures with glass panes as roof covering. An interesting different concept is the use of the principle of steel space grid structures and improve their transparency by the activation of glass panes in the compression layer for the transfer of in-plane forces.The intention of this study is to point out the potential of space grid structures with steel-glass module in roof applications. The basic principle of these new transparent space structures is the strict replacement of bar members in the compression layer by glass panes. At the example of a plain double layer grid the transformation from traditional steel space grid structures to space grid structures made of steel-glass-modules is described.