The Integrated Approach to Structural Glass Safety Applied to Glass Beams

This paper presents a safety classification of 14 different of glass beam designs based on experimental research, using the Integrated Approach to Structural Glass Safety (introduced by the author, [1], [2]). The design parameters included the  number of layers (2 or 3), the level of prestress (annealed, heat strengthened, thermally tempered), and laminate type (PVB or SG). Additionally, steel reinforced glass beams were tested. Three different methods were applied to obtain completeredundancy curves (development of residual strength under increasing levels of damage): 4-point bending after no, partial, or full damage. The damage was applied by a custom made impact device consisting of a spring loaded flat steel head thatimpacted the edges of the glass layers of the beams. The resulting Element Safety Diagrams of each design is discussed. Relativized curves are used to compare the safety of the designs

Editorial

The 7th edition of Challenging Glass is unlike any of the previous events in the 12-year history of the conference. Due to the ongoing corona pandemic, the on-location event has been replaced by an online webinar, featuring a keynote by Chikara Inamura and a small selection of short paper presentations. We are proud to, nevertheless, be able to present to you these Challenging Glass Conference 7 Proceedings, which are published Open Access in collaboration with TU Delft Open. The proceedings contain more than 50 papers, by glass experts from around the world, while another 20 papers are published in collaboration with the Springer journal Glass Structures & Engineering. We appreciate the efforts by all authors in these extraordinary times immensely. Organising this webinar and editing the conference proceedings has once again been an enjoyable experience, albeit different from previous ones. We would like to acknowledge all authors for their contributions, all scientific committee members for their valuable reviews, our esteemed keynote speaker for his inspiring presentation and of course all webinar participants for their interest in this event. We are grateful to our Platinum Sponsors Saint-Gobain and Eastman, as well as our Gold and Silver Sponsors for making this event possible. In addition, we would like to thank our hosting institution, Ghent University, particularly Shahryar Nategh for his support in compiling the conference proceedings. We wish you an enjoyable webinar and we trust you will encounter inspiring publications in these proceedings

Editorial

The 7th edition of Challenging Glass is unlike any of the previous events in the 12-year history of the conference. Due to the ongoing corona pandemic, the on-location event has been replaced by an online webinar, featuring a keynote by Chikara Inamura and a small selection of short paper presentations.    We are proud to, nevertheless, be able to present to you these Challenging Glass Conference 7 Proceedings, which  are published Open Access in collaboration with TU Delft Open. The proceedings contain more than 50 papers, by glass experts from around the world, while another 20 papers are published in collaboration with the Springer journal Glass Structures & Engineering. We appreciate the efforts by all authors in these extraordinary times immensely. Organising this webinar and editing the conference proceedings has once again been an enjoyable experience, albeit different from previous ones. We would like to acknowledge all authors for their contributions, all scientific committee members for their valuable reviews, our esteemed keynote speaker for his inspiring presentation and of course all webinar participants for their interest in this event. We are grateful to our Platinum Sponsors Saint-Gobain and Eastman, as well as our Gold and Silver Sponsors for making this event possible. In addition, we would like to thank our hosting institution, Ghent University, particularly Shahryar Nategh for his support in compiling the conference proceedings. We wish you an enjoyable webinar and we trust you will encounter inspiring publications in these proceedings.   Jan Belis, Freek Bos & Christian Louter Conference Organisers September 202

Edge strength of core drilled and waterjet cut holes in architectural glass

In structural glass design, an often-applied connection is a bolted connection subjected to in-plane tensile loads. Traditionally, the hole in the glass pane is manufactured by core drilling and conical edge finishing. An alternative method is by waterjet cutting the holes, resulting in cylindrically shaped holes. This research compares the edge strength of core drilled and waterjet cut holes. It focuses on in-plane tensile tests and consists of an experimental part in combination with a numerical part. In the in-plane tensile tests, peak stresses occur perpendicular to the load direction. These stresses are found to be higher for waterjet cut holes (+ 13%) compared to core drilled holes. As a result, the characteristic ultimate load is lower for waterjet cut holes (− 16%). Furthermore, the influence of thermally toughening the glass is found to be more favourable for the characteristic ultimate load of specimens containing core drilled holes than it is for waterjet cut holes. Next to that, it was found that the ultimate load linearly increases with the panel thickness. Eccentric loading, caused by insufficient bushing material or rotation of the bolt, only slightly decreases the ultimate load, provided that no hard contact between bolt and glass occurs. In addition, coaxial double ring tests were performed in the hole area, showing that waterjet cut holes result in larger stresses near the hole edge than core drilled holes. Furthermore, waterjet cut holes are found not to be perfectly round, while drilled holes are. This un-roundness negatively influences the ultimate load and the stresses in the glass; the larger the extent of un-roundness, the higher the stresses and the lower the ultimate load. Also, the orientation of the un-round hole is of influence on the stresses and ultimate load for the tensile test. It is concluded that waterjet cut holes result in lower characteristic ultimate loads and higher stresses. Due to the different edge finishing, the ultimate load still is lower compared to core drilled holes, even if the waterjet cut holes are perfectly round

Double curved concrete printing: printing on non-planar surfaces

It is no secret that there have been some great advances in the realm of concrete additive manufacturing. However, one of the major drawbacks of this fabrication technique is that the elements must be self-supporting during printing. While most other additive manufacturing materials can overcome this by using a secondary printed support structure, alternative strategies have to be developed for materials such as concrete. This 4TU project explores the possibilities of combining concrete additive manufacturing with a temporary support surface. By printing on a free-form surface, more intricate geometries can be realized. A number of potential applications have been outlined, however the principle focus is combining concrete additive manufacturing and casting. The end result is a partially-printed pavilion using a completely digital design-tofabrication workflow

Editorial

Welcome at Challenging Glass! At this 9th edition of the conference, we are thrilled to welcome no less than 120 presentations - a record since the first edition of this international event back in 2008. Ever since, we have been keeping up our high standards in sharing knowledge, science and best practices on glass engineering and design. Thanks to the great work of bright authors and sharp reviewers, that is not different this time. What actually ís different this edition, is the introduction of a Glass Circularity Debate. We have seen several trends come and go over the past years, but the importance of circular design is to stay! Therefore, on top of the regular technical sessions on the topic, we bring five speakers to the stage who will pitch their views on the circular use of glass and discuss it with each other and the audience. You are warmly invited to actively participate! Furthermore, we are happy to welcome no less than five top-notch keynote speakers. The first keynote will focus on the Mirage project and will be delivered jointly by Dr Faidra Oikonomopoulou, Dr Telesilla Bristogianni and Mr Alexandros Cannas. The second keynote will be presented by Dr Peter Zoon, who will explain how glass plays an important role in crime scene investigations. It promises to be a criminal talk! Last but not least, Dr Corentin Fivet will share his work on new design paradigms for reuse during his closing plenary lecture. During the conference you will be able to retrieve all abstracts and papers, but also presenter details and programme updates with our conference app. After the conference, all papers will be available online, either through our online proceedings platform or through the peer-reviewed journal Glass Structures & Engineering (SpringerNature). We explicitly like to thank the continuous support of our sponsors, Scientific Committee members, authors and attendees. Together with you and with our co-hosts James O’Callaghan, Mauro Overend and Fred Veer we are eager to kick off Challenging Glass 9! Christian Louter, Freek Bos and Jan Belis June 202

Automated image segmentation of 3D printed fibrous composite micro-structures using a neural network

A new, automated image segmentation method is presented that effectively identifies the micro-structural objects (fibre, air void, matrix) of 3D printed fibre-reinforced materials using a deep convolutional neural network. The method creates training data from a physical specimen composed of a single, straight fibre embedded in a cementitious matrix with air voids. The specific micro-structure of this strain-hardening cementitious composite (SHCC) is obtained from X-ray micro-computed tomography scanning, after which the 3D ground truth mask of the sample is constructed by connecting each voxel of a scanned image to the corresponding micro-structural object. The neural network is trained to identify fibres oriented in arbitrary directions through the application of a data augmentation procedure, which eliminates the time-consuming task of a human expert to manually annotate these data. The predictive capability of the methodology is demonstrated via the analysis of a practical SHCC developed for 3D concrete printing, showing that the automated segmentation method is well capable of adequately identifying complex micro-structures with arbitrarily distributed and oriented fibres. Although the focus of the current study is on SHCC materials, the proposed methodology can also be applied to other fibre-reinforced materials, such as fibre-reinforced plastics. The micro-structures identified by the image segmentation method may serve as input for dedicated finite element models that allow for computing their mechanical behaviour as a function of the micro-structural composition

Optimizing 3D concrete printing: exploring potentials and limitations of materials and production

The application of new Computer Aided Manufacturing (CAM), digital fabrication and additive manufacturing techniques in the construction industries is expected to bring major change to these industries. Driven by a foreseen reduction of construction time and labor cost, simplification of logistics and an increase of constructible geometrical freedom, many experiments are performed both at academia and in practice. Beyond these economical and architectural objectives, digital fabrication in construction can be used to reduce the environmental footprint of the industry. The increased level of control offered by digital fabrication enables the use of advanced computational optimisation techniques. With these optimisation techniques buildings can be designed which, for instance, combine an optimal thermal performance with a minimum use of materials, while still complying with all codes and standards. In order to fully utilise this potential of digital fabrication, the capabilities and limitations of the manufacturing process need to be taken into account during optimisation. By combining the concrete 3D printing knowledge of Eindhoven University of Technology, the optimisation expertise of the BEMNext lab at Delft University of Technology and software development by White Lioness technologies, the ‘Optimising 3D concrete printing’ Lighthouse project has made the first steps towards more knowledge on integrated optimisation and manufacturing