Bernhard Weller

Outline of Testing and Evaluation Program Used in Selection of Adhesives for Transparent Adhesive Joints in All-Glass Load-Bearing Structures

Architects are increasingly demanding all-glass load-bearing structures with fully transparent adhesive joints. Usually, such structures are classed as nonregulated forms of construction. The Institute of Building Construction at Dresden’s Technische Universitat has now obtained the first individual approvals in Germany for all-glass structures with transparent adhesive joints for two buildings in Dresden and Grimma. In these cases, the loads are carried via load-bearing glued frames that rely on a material bond between the individual parts without any metal fixings. This solution is based on the results of many years of development. Currently, various frame corners covering a wide range of parameters are being studied in a follow-up project. The aim is to optimize the adhesive joints and the bonding technology. The requirements placed on the joint are being identified and corresponding adhesive systems researched. Preliminary studies of numerous material specimens form the starting point for determining the material parameters. Small-scale specimens are being tested under various boundary conditions and aging scenarios to establish the strengths of a number of suitable adhesives. These results will enable prototypes to be designed for numerical simulation. Numerical calculations and experimental investigations are being carried out in parallel to optimize the geometry, load-carrying capacity, long-term reliability, and durability of the glued all-glass frame corners. Specimen components are loaded in a testing machine to study the structural effect of these glued glass frame corners. The findings will be incorporated in the design of the adhesive joint and in the development of a numerical simulation for the glued connection. Data for executing an adhesive joint, specific to each adhesive and crucial for the quality of the transparency, conclude the project.

Experimental Evaluation of Ultraviolet and Visible Light Curing Acrylates for Use in Glass Structures

Adhesive joints in glass construction have been realized with one- and two-component silicones for more than 20 years. However, ultraviolet and visible light curing acrylates in glass constructions provide additional design potential due to their inherent transparency, their advantages in regard to the production process, and their increased material strength. The aging behavior of these adhesives was comprehensively examined by testing bonded joints of annealed glass and metal to gain in-depth knowledge of their durability. The study was expanded by testing full-scale samples of various glass applications.

Adhesive Joints in Glass and Solar Engineering

The architecture of the past 100 years is characterized by a desire for ever greater transparency. Inevitably, that goes hand in hand with a constantly growing proportion of glass in the building envelope. But owing to the brittle nature of glass, there are only limited options for transferring tried-and-tested methods of jointing—derived from structural steelwork and other engineering disciplines—to this material. However, adhesive joints are much more suited to creating a material bond between glass components. Structural adhesive joints for load bearing glass components have been the subject of research and development work all over Europe in recent years. This article looks at some of that work. The research has led to the development of practical adhesive joints for glass-glass and glass-metal connections. The work includes the study of surface pretreatments and aging scenarios so that types of application for the tensile and shear loads encountered in practice can be specified. Material specimens tested at various load application rates and temperatures enable the material parameters to be determined. A torsion specimen with a glued butt joint is being used to improve the in situ testing of glass-metal connections. There are plenty of potential applications for adhesive joints in structural glazing and solar technology, including the following: Point adhesive joints for overhead glazing and for oversize photovoltaic modules subjected to high environmental loads, linear adhesive joints for hybrid steel-glass composite beams with good ductility and for glass fins with a reduced cross-section in minimized steel-and-glass facades, or full-bond adhesive joints for photovoltaic facades suspended in front of a ventilation cavity and for fully transparent load bearing adhesive joints to an all-glass pavilion (first approved application in Germany).

Evaluation of joining methods for novel timber–aluminum composite profiles for innovative louver windows and facade elements

ABSTRACT The demand for efficient buildings requires improvement in window and facade design. Aluminum and steel dominate the solutions for large facades while wood is used on a much smaller scale. In order to widen the scope of wood application in facades, this paper assessed novel timber–aluminum composite profiles which have been developed for louver windows. The research focused on two different technologies suitable for joining wood to other parts of the louver window. First, the study assessed the adhesive bond between the glass unit and the wooden part of the profile. The evaluation focused on seven different wood substrates ranging from solid softwoods and hardwoods to wood-based products and modified wood. Second, a specific rolling technique was applied to join the wooden section to the aluminum component. The technology was taken from the prefabrication process of conventional composite profiles. There, plastic insulating bars are clamped onto the aluminum profiles. This joining method had not been applied to timber so far. The results show that beech wood has the most suitable properties for use in such composite profiles. The composite frames examined provide a lower energy footprint compared to standard solutions. They enable a sustainable yet durable solution for the building envelope.

Experimental study of the pull-out resistance of alternative high-strength fasteners for wood-based materials

ABSTRACT More curtain-wall facings are fastened non-visibly to create a uniform building surface. As a consequence of bigger panels and the invisible attachment, the load effects on the fasteners and the fixing areas of the panels are increased. These include the tare weight and the tensile load due to the wind load. Therefore, this study assessed the tensile load of novel fasteners in two different wood materials. A new façade panel material is high-pressure laminate. It consists of cellulose layers soaked in epoxy resin. The second tested material was a modified pine wood, which is produced by impregnation and subsequent heat-curing. It is comparable to highly durable tropical wood. The survey focused on three alternative fixing materials such as screw inserts, drive-in nuts and undercut anchors. The pull-out resistance and failure pattern of the specimens with an alternative fastener are compared to those with wood screws. Furthermore, it was tested whether different temperatures between −20°C and +80°C have an impact on it. The results demonstrate that the alternative fasteners are much more effective than normal wood screws. The pull-out resistance out of the same thin plate material was up to four times higher.

Bewertung der energetischen Qualität von Verglasungen am Campus der TU Dresden

In der Praxis konnen die thermischen Schwachstellen in der Gebaudehulle – die Fenster – mittels Thermografieaufnahmen qualitativ abgebildet werden. Offen bleibt jedoch die quantitative Bewertung der eingebauten Verglasung, da der Warmedurchgangskoeffizient der Verglasung (Ug-Wert) durch diese Aufnahmen nicht bestimmbar ist. Somit kann auch keine Aussage getroffen werden, ob die Anforderungen an den vorgegebenen Warmeschutz erfullt werden. Schlussendlich konnen die Aussagen uber die Qualitat der Verglasung lediglich getroffen werden, wenn der vor Ort gemessene Ug-Wert bekannt ist.

Nutzung von Solarenergie im Campusquartier

Die TU Dresden verzeichnet durch Campuserweiterungen und intensivierte Nutzung seit Jahren einen kontinuierlich ansteigenden Elektroenergieverbrauch. Im Jahr 2015 belief sich dieser auf 56 GWh [1], was nach aktuellen Angaben des BDEW [2] naherungsweise dem Stromverbrauch privater Haushalte einer Stadt mit ca. 40.000 Einwohnern entspricht. Der damit verbundene Kohlendioxid(CO2)-Ausstos erreichte mit ca. 25.000 t einen neuen Hochststand.

Das Pinguincafé im Dresdner Zoo – Nutzungskonzept für einen Wiederaufbau

Bei dem Pinguincafe handelt es sich um ein Zeugnis der Nachkriegsarchitektur der DDR, welches uber mehrere Jahrzehnte Bestandteil der gastronomischen Strukturen im Dresdner Zoo war. Von 1973 bis 2015 konnten hier bis zu 50 Gaste im Innenbereich und zusatzlich weitere 200 Personen auf der Terrasse bewirtet werden.

Louvre Lens ‐ Einfachheit und Komplexität

Die Gebaudehullen des Louvre Lens in Nordfrankreich vereinen nicht nur hochste gestalterische und materielle Anforderungen, sondern reagieren auch auf die strukturellen und bauphysikalischen Besonderheiten der schlanken, eingeschossigen Museumsbauten. Insbesondere die hohen Herausforderungen in der Planung der verglasten Gebaudehullen werden beschrieben und die wahrend des siebenjahrigen Prozesses entwickelten Losungsansatze erlautert. Louvre Lens – Simplicity and Complexity. The building envelopes of the Louvre museum in Lens in Northern France combine highest aesthetic and material requirements. They respond to the structural and physical characteristics of the slender single-storey buildings. The facade engineering of the envelopes will be described with regard to the high requirements and to the seven year process from scratch to inauguration, with main focus on the glazed parts.

Baukonstruktion im Bestand

Ausgangspunkt einer denkmalpflegerischen und energetischen Bewertung eines Gebaudes sollten die baukonstruktive Analyse und die Dokumentation der Bausubstanz bilden. Als hilfreich kann sich hierbei eine Differenzierung nach dem jeweiligen Baualter des Gebaudes erweisen. Im uberwiegenden Teil des Gebaudebestandes spiegeln sich historische Prozesse wider, die zwar regional und sozial unterschiedlich abliefen, aber doch innerhalb begrenzter Zeitabschnitte erkennbare Gemeinsamkeiten aufweisen. Aus diesem Grund hat sich die Einteilung nach Baualtersstufen beziehungsweise nach Baualtersklassen fur einen grundsatzlichen Uberblick uber haufig anzutreffende Baukonstruktionen und deren energetische Probleme bewahrt.