Webinar

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About the speakers: 

New Content ItemSteffen Feirabend studied structural engineering at the University of Stuttgart and the University of Calgary. In March 2000 he began his professional career as a structural engineer with Werner Sobek. Later he also started his research activity with Werner Sobek at the Institute for Lightweight Structures and Conceptual Design (ILEK) where he prepared his PhD thesis about the post-breakage behavior of laminated glass. He also worked as head of the steel/glass at seele GmbH on complex building envelopes combining design and construction.

His focus is on the design, analysis, modeling and construction of complex spatial structures and building envelopes as well as the use of Building Information Modelling (BIM) over the buildings lifetime to create a sustainable future.

He worked worldwide on projects e.g. the museum “The Broad” in Los Angeles (USA), the “EXPO2017” (Kazakhstan) and the railway station “Stuttgart21” as well as airports, high rises and stadiums.


New Content ItemSteffen Dix started his career with an apprenticeship as a technical draftsman at seele GmbH and then studied civil engineering with focus on steel, lightweight and glass construction at the University of Applied Sciences in Munich. (During this time, he spent six months in New York, where he worked as an assistant site manager on the construction of the Apple Stores at 5th Avenue and Grand Central Station.)

Since the beginning of his studies he worked in the laboratory for steel and light metal construction (LSL). First as a working student, under Ömer Bucak, until today as a Research Assistant under Christian Schuler. Since 2016, his research focus is on quality control of tempered glass, which has resulted in his currently ongoing PhD project "Methods for the evaluation of optical anisotropy effects in tempered glass".

He is currently pursuing his PhD via a cooperative doctorate at the Institute for Mechanics and Materials in Gießen under Stefan Kolling.


Summary of Content: 

The Messeturm - Trade Fair Tower – in Frankfurt”, by S. Feirabend

The talk will be based on the recently published article:New Content Item
Feirabend, S., Starz, F., Bechmann, R. et al. Repositioning Messeturm–Maximum Transparency. Glass Struct Eng (2020). https://doi.org/10.1007/s40940-020-00140-8

Which can be found here: https://rdcu.be/ch9ie

Abstract:
The Messeturm (“Trade Fair Tower”) in Frankfurt is currently adjusted to the requirements of a modern office building. The lobby area has been enlarged by a highly transparent façade consisting of oversized insulating glass (IG) units. The IG units are curved and have a size of up to 17 m × 2.8 m. To obtain a perfectly curved façade, the IG units were fabricated with laminated cold-bended glass panes. Horizontally the IG units are supported by tapered stainless steel fins. Inclined steel beams connect the top of the façade fins with the tower structure creating a rounded roof. The vertical façade with its glass roof allows maximum transparency for people inside the lobby as well as for people passing by outside to the nearby trade fair grounds. The glass was fabricated by sedak. The façade was installed by seele on behalf of the owner OFFICEFIRST, the asset-management of Blackstone. 

“Digital Evaluation of Optical Anisotropy in Tempered Glass”, by S. Dix.

The talk will be based on the recently published article:New Content Item
Dix, S., Müller, P., Schuler, C. et al. Digital image processing methods for the evaluation of optical anisotropy effects in tempered architectural glass using photoelastic measurements. Glass Struct Eng 6, 3–19 (2021). https://doi.org/10.1007/s40940-020-00145-3

Which can be found here: https://rdcu.be/ch9i5


Abstract:
Optical anisotropy effects in architectural glass can be evaluated using digital image processing. Hereby, thermally toughened glass panes were analyzed quantitatively using a circular polariscope. Glass subjected to externally applied stresses or residual stresses becomes birefringent. Polarized light on birefringent materials causes interference colors (iridescence), referred to as anisotropies, which affect the optical appearance of glass panes in building envelopes. Thermally toughened glass, such as toughened safety glass or heat strengthened glass, show these iridescences due to thermally induced residual stress differences. RGB-photoelastic full-field methods allow the quantitative measurement of anisotropies, since the occurring interference colors are related to the measured retardation values. By calibrating the circular polariscope, retardation images of thermally toughened glass panes are generated from non-directional isochromatic images using computer algorithms. The analysis of the retardation images and the evaluation of the anisotropy quality of the glass is of great interest in order to detect and sort out very low quality glass panes directly in the production process. Therefore, retardation images are acquired from different thermally toughened glass panes then different image processing methods are presented and applied. It is shown that a general definition of exclusion zones, e.g. near edges is required prior to the evaluation. In parallel, the limitations in the application of first-order statistical and threshold methods are presented. The intend of the investigation is the extension of the texture analysis based on the generation of Grey Level Co-occurrence Matrices, where the spatial arrangement of the retardation values is considered in the evaluation. For the first time, the results of textural features of different glass pane formats could be compared using reference areas and geometry factors. By reduction of the original image size, the computation time of textural analysis algorithms could be remarkably speeded up, while the textural features remained the same. Finally, the knowledge gained from these investigations is used to determine uniform texture features, which also includes the pattern of anisotropy effects in the evaluation of thermally toughened glass. Together with a global evaluation criterion this can now be implemented in commercial anisotropy measurement systems for quality control of tempered architectural glass. 



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