This dissertation proposes the Integrated Approach to Structural Glass Safety, based on four clea... more This dissertation proposes the Integrated Approach to Structural Glass Safety, based on four clearly defined element safety properties, damage sensitivity, relative resistance, redundancy, and fracture mode. The Element Safety Diagram (ESD) is introduced to provide an easy-to-read graphical representation of these properties. The safety performance of a large number of glass beam designs has been compared through experimental testing based on the proposed approach. The effects of a wide range of safety enhancing design measures on each element safety property is extensively discussed. Elastic strain energy release is identified as a, hitherto underexposed, parameter with major influence on redundancy – the most important safety property. Finally, the Integrated Approach is applied to re-evaluate the safety of two full-scale case-study projects which started this study.
It is no secret that there have been some great advances in the realm of concrete additive manufa... more 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-to-fabrication workflow.
High Tech Concrete: Where Technology and Engineering Meet, 2017
Recent years have seen a rapid growth of additive manufacturing methods for concrete construction... more Recent years have seen a rapid growth of additive manufacturing methods for concrete construction. Generally, these methods are based on a linear sequence of design → print path definition → actual printer actions in a print environment. However, printing experiments show that a large number of parameters influence the printing process. Not all of these can be predicted accurate on forehand. Therefore, a method is introduced that allows real-time adjustment of the print process. As a proof-of-concept, a measurement system for the nozzle height has been developed and tested. Because this variable relates to machine properties, environmental conditions as well as material behaviour, it is a crucial parameter to control. In two case study prints, the effectiveness of the device was shown. In one study, the printer could follow a range of irregular curves in the print bed, whereas only a simple flat rectangular print path had been programmed. In the other, it was shown the print path could be adjusted to vertical deformation of the previous layers of printed filament in a tubular object of several dozen layers. Thus, premature failure through irregular loading of the object during printing was avoided. Further expansion of the use of real-time measurement devices may be anticipated in the future. Besides more advanced geometrical measuring, chemical and physical conditions such as concrete temperature (both before and after deposition), surface wetness, and environment humidity, can be recorded. Combined with the machine action log, this should result in a detailed set of as-built data of the printed object, allowing e.g. for a geometrical clash control with the design as well as other quality controls.
A particularly difficult aspect of glass structures is the joining together of structural members... more A particularly difficult aspect of glass structures is the joining together of structural members. The various tasks of a joint usually can not be fulfilled by glass alone. Therefore, steel intermediate components are often applied, but since these are opaque, they form an obstacle towards the development of completely transparent structures. Transparent polymers may provide an alternative. There are literally hundreds of transparent polymers available on the market. Their individual material properties vary significantly, but they share an even bigger dissimilarity with the properties of steels. This study therefore continues on previous research to identify suitable transparent polymers. Information has been collected from material data sheets. Furthermore, a number of tensile tests on material specimens as well as specimens with steel bolt inserts, has been performed. Consecutively, a common structural glass joints was analyzed by determining the typical loads acting on it. A rou...
Existing methods to asses the safety of glass structures are insufficient. Although it is general... more Existing methods to asses the safety of glass structures are insufficient. Although it is generally recognized that a (codified) probability analysis does not consider all relevant structural safety aspects, individual safety demands on structural glass elements, besides a maximum failure probability, are often not entirely clear in their aim, as well as not related to each other. There is a lack of identifiable element safety properties. As a result, there is much confusion and discussion in professional practice. In an attempt to achieve some clarity in the debate and to obtain objective criteria to compare structural glass designs with regard to safety, the Integrated Approach to Structural Glass Safety is proposed. Four properties of the glass elements are defined: resistance, damage sensitivity, redundancy, and fracture mode. They are graphically combined in the Element Safety Diagram. Several underlying concepts, such as load transfer mechanisms, initial and final failure, and damage, are also introduced. Performance requirements can be formulated to which each element safety property can be checked. Together, the defined safety properties and performance criteria form a new approach to structural glass safety
A specific problem in the development of tubular glass structural members, is their connection to... more A specific problem in the development of tubular glass structural members, is their connection to the external structure. The option of glueing in an acrylic part at the tube ends has been investigated. The cylindrical bond shape poses special difficulties with regard to the application and curing of the adhesive as well as the differences in thermal expansion of the glass and the acrylic. The first part of the research aimed at the proper joint design and adhesive application method, while the second part consisted of investigating the joint shear strength. As a variant, a joint with an acrylic part glued into an acrylic tube was also investigated. In both cases, joint strengths of over 10 kN were reached, which was enough for application in an experimental structure the author is currently working on
Glass is generally considered to be an unsafe material to use in building structures. To limit th... more Glass is generally considered to be an unsafe material to use in building structures. To limit the risk associated with glass structures, there has been a focus on the probabilistic approach. This is insufficient for structures in general and for glass structures in particular. Much more than common structural materials like steel and reinforced concrete, glass is highly susceptible to a wide range of incidents causing glass breakage. Therefore, one should not (only) ask ‘when will the glass break?’ (probabilistic approach), but (also) ‘what will happen when is does?’ (consequence-based approach). Analysis of projects realized in practice show that structural engineers are aware of this, and use varying strategies to limit the consequences of glass failure. However, such strategies are applied to varying extent, depending on the engineer’s experience and opinion, location, structure type and probably on many more factors. Hence, an explicit consequence-based approach is proposed for...
Although there is an increasing desire to apply structural adhesive bonds in glass constructions,... more Although there is an increasing desire to apply structural adhesive bonds in glass constructions, the lack of a reliable failure criterion is a major obstacle. Since the average overlap shear strength values normally provided cannot be applied as a general limit for arbitrary adhesive bond geometries, extensive testing has to be performed on any new design to ensure its structural performance and safety. Not only the building industry, also maritime, aeronautical and car industries are struggling with this issue. To supply a contribution, this paper provides a numerical analysis of the stress distributions in an adhesive layer during a single lap shear test as was performed at Ghent University. Firstly, an appropriate mesh and element type was chosen after which the influence of different geometries on the peak shear stress was investigated. Additionally, simulations with different stiffness levels for the adhesive were performed. From the numerical analysis, it could be concluded t...
Industrial and academic partners from the Netherlands realized the world’s first 3D concrete prin... more Industrial and academic partners from the Netherlands realized the world’s first 3D concrete printed bicycle bridge. Certification safe use in practice was obtained through the concept of “Design by Testing”. Innovative reinforcement concepts were applied to guarantee safe failure behaviour. This paper discusses the design, testing, manufacturing and assembling of the bridge.
The application of new Computer Aided Manufacturing (CAM), digital fabrication and additive manuf... more 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 l...
Case study projects based on Digitally Fabricated Concrete (DFC) are presented in an increasing p... more Case study projects based on Digitally Fabricated Concrete (DFC) are presented in an increasing pace around the globe. Generally, though, it is not reported what structural requirements (if any) these structures meet and how compliance to these requirements was established. Published material research is often not connected to the presented case studies, and even when it is, it is not necessarily obvious their small scale results can be applied to full scale structures as some scale effects should be anticipated. Caution is required as DFC related material tests are still under development and scale effects in DFC have hardly been studied. Therefore, it is recommendable to perform large scale testing, in the range of 1:5 to 1:1, if DFC is applied to actual use structures. This paper presents such testing for two projects, a pavilion in Denmark (not realized) and a bridge in the Netherlands (realized). In both cases, elements printed with the 3D Concrete Printing facility of the Eindhoven University of Technology were intended for actual load bearing performance. The conservative designs past the test requirements, but nevertheless some important findings with regard to element manufacturing and structural behaviour were experienced. It is concluded that large scale testing remains advisable for DFC structures as long as not all relevant aspects of the technology are quantitatively understood, at least when new concepts are being applied.
High Tech Concrete: Where Technology and Engineering Meet, 2017
Additive manufacturing and 3D printing are rapidly developing digital fabrication techniques (Lu ... more Additive manufacturing and 3D printing are rapidly developing digital fabrication techniques (Lu et al. 2015). After the first steps in small scale printing of metals (Frazier 2014) and plastics (Gibson et al. 2014) have been made, research from various groups around the world is now also focusing on large scale printing in concrete (Lim et al. 2012) and making this technology more suitable for the construction scale. The potential of using this technology is that it will be possible to create complex and/or customised concrete designs with the expectation that the costs will be low and the construction speeds will be high. Additionally, this new technology will provide opportunities to create more efficient structures. Structures can already be optimised in the early stages of the design for weight and structural performance, but the resulting optimised structures are often difficult to manufacture due to the resulting geometry of the design. Additive manufacturing can address this issue without high costs for moulds and labour.
The lack of available reinforcement methods suitable for extrusion-based 3D concrete printing is ... more The lack of available reinforcement methods suitable for extrusion-based 3D concrete printing is well known. Because conventional methods using pre-placed steel bars are incompatible with this manufacturing method, several alternatives are under development. This paper introduces a novel reinforcement application method, based on screwing. Contrary to placement methods based on pushing, i.e. only a translational movement, the combination of translation and rotation inherent in the screwing motion, allows a practically void-free mechanical interlock with which a high level of bond can be attained. The concept makes use of the fact that the print mortar is still highly pliant for some time after deposition, allowing screws to be inserted without fracturing the concrete. The translational-rotational movement needs to be externally controlled, as the material at the early age does not provide sufficient resistance to pull in the screw on application of the rotation. Pull-out tests from printed and cast samples and 3-point bending tests on printed specimens showed a high bond strength and thus underline the feasibility of this concept.
1= glass structure 2= annealed glass 3= failure behaviour 4= design stress Abstract An experiment... more 1= glass structure 2= annealed glass 3= failure behaviour 4= design stress Abstract An experimental transparent pavilion of 9 x 9 x 3.6 m3 has been designed. It combines various innovative concepts like stainless steel reinforced glass beams, resin laminated glass columns, acrylic joints and glass façade elements with glued on fins. However, it's most distinctive feature is the fact that none of the glass is heat-strengthened or tempered. This is part of a revolutionary safety concept stating that failure behaviour similar to that of reinforced concrete is obtainable and desirable for glass structures. This concept is formulated and it's consequences for the structural design of the pavilion are explained. Furthermore, several innovations in the design possibilities of transparent structures are presented.
This dissertation proposes the Integrated Approach to Structural Glass Safety, based on four clea... more This dissertation proposes the Integrated Approach to Structural Glass Safety, based on four clearly defined element safety properties, damage sensitivity, relative resistance, redundancy, and fracture mode. The Element Safety Diagram (ESD) is introduced to provide an easy-to-read graphical representation of these properties. The safety performance of a large number of glass beam designs has been compared through experimental testing based on the proposed approach. The effects of a wide range of safety enhancing design measures on each element safety property is extensively discussed. Elastic strain energy release is identified as a, hitherto underexposed, parameter with major influence on redundancy – the most important safety property. Finally, the Integrated Approach is applied to re-evaluate the safety of two full-scale case-study projects which started this study.
It is no secret that there have been some great advances in the realm of concrete additive manufa... more 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-to-fabrication workflow.
High Tech Concrete: Where Technology and Engineering Meet, 2017
Recent years have seen a rapid growth of additive manufacturing methods for concrete construction... more Recent years have seen a rapid growth of additive manufacturing methods for concrete construction. Generally, these methods are based on a linear sequence of design → print path definition → actual printer actions in a print environment. However, printing experiments show that a large number of parameters influence the printing process. Not all of these can be predicted accurate on forehand. Therefore, a method is introduced that allows real-time adjustment of the print process. As a proof-of-concept, a measurement system for the nozzle height has been developed and tested. Because this variable relates to machine properties, environmental conditions as well as material behaviour, it is a crucial parameter to control. In two case study prints, the effectiveness of the device was shown. In one study, the printer could follow a range of irregular curves in the print bed, whereas only a simple flat rectangular print path had been programmed. In the other, it was shown the print path could be adjusted to vertical deformation of the previous layers of printed filament in a tubular object of several dozen layers. Thus, premature failure through irregular loading of the object during printing was avoided. Further expansion of the use of real-time measurement devices may be anticipated in the future. Besides more advanced geometrical measuring, chemical and physical conditions such as concrete temperature (both before and after deposition), surface wetness, and environment humidity, can be recorded. Combined with the machine action log, this should result in a detailed set of as-built data of the printed object, allowing e.g. for a geometrical clash control with the design as well as other quality controls.
A particularly difficult aspect of glass structures is the joining together of structural members... more A particularly difficult aspect of glass structures is the joining together of structural members. The various tasks of a joint usually can not be fulfilled by glass alone. Therefore, steel intermediate components are often applied, but since these are opaque, they form an obstacle towards the development of completely transparent structures. Transparent polymers may provide an alternative. There are literally hundreds of transparent polymers available on the market. Their individual material properties vary significantly, but they share an even bigger dissimilarity with the properties of steels. This study therefore continues on previous research to identify suitable transparent polymers. Information has been collected from material data sheets. Furthermore, a number of tensile tests on material specimens as well as specimens with steel bolt inserts, has been performed. Consecutively, a common structural glass joints was analyzed by determining the typical loads acting on it. A rou...
Existing methods to asses the safety of glass structures are insufficient. Although it is general... more Existing methods to asses the safety of glass structures are insufficient. Although it is generally recognized that a (codified) probability analysis does not consider all relevant structural safety aspects, individual safety demands on structural glass elements, besides a maximum failure probability, are often not entirely clear in their aim, as well as not related to each other. There is a lack of identifiable element safety properties. As a result, there is much confusion and discussion in professional practice. In an attempt to achieve some clarity in the debate and to obtain objective criteria to compare structural glass designs with regard to safety, the Integrated Approach to Structural Glass Safety is proposed. Four properties of the glass elements are defined: resistance, damage sensitivity, redundancy, and fracture mode. They are graphically combined in the Element Safety Diagram. Several underlying concepts, such as load transfer mechanisms, initial and final failure, and damage, are also introduced. Performance requirements can be formulated to which each element safety property can be checked. Together, the defined safety properties and performance criteria form a new approach to structural glass safety
A specific problem in the development of tubular glass structural members, is their connection to... more A specific problem in the development of tubular glass structural members, is their connection to the external structure. The option of glueing in an acrylic part at the tube ends has been investigated. The cylindrical bond shape poses special difficulties with regard to the application and curing of the adhesive as well as the differences in thermal expansion of the glass and the acrylic. The first part of the research aimed at the proper joint design and adhesive application method, while the second part consisted of investigating the joint shear strength. As a variant, a joint with an acrylic part glued into an acrylic tube was also investigated. In both cases, joint strengths of over 10 kN were reached, which was enough for application in an experimental structure the author is currently working on
Glass is generally considered to be an unsafe material to use in building structures. To limit th... more Glass is generally considered to be an unsafe material to use in building structures. To limit the risk associated with glass structures, there has been a focus on the probabilistic approach. This is insufficient for structures in general and for glass structures in particular. Much more than common structural materials like steel and reinforced concrete, glass is highly susceptible to a wide range of incidents causing glass breakage. Therefore, one should not (only) ask ‘when will the glass break?’ (probabilistic approach), but (also) ‘what will happen when is does?’ (consequence-based approach). Analysis of projects realized in practice show that structural engineers are aware of this, and use varying strategies to limit the consequences of glass failure. However, such strategies are applied to varying extent, depending on the engineer’s experience and opinion, location, structure type and probably on many more factors. Hence, an explicit consequence-based approach is proposed for...
Although there is an increasing desire to apply structural adhesive bonds in glass constructions,... more Although there is an increasing desire to apply structural adhesive bonds in glass constructions, the lack of a reliable failure criterion is a major obstacle. Since the average overlap shear strength values normally provided cannot be applied as a general limit for arbitrary adhesive bond geometries, extensive testing has to be performed on any new design to ensure its structural performance and safety. Not only the building industry, also maritime, aeronautical and car industries are struggling with this issue. To supply a contribution, this paper provides a numerical analysis of the stress distributions in an adhesive layer during a single lap shear test as was performed at Ghent University. Firstly, an appropriate mesh and element type was chosen after which the influence of different geometries on the peak shear stress was investigated. Additionally, simulations with different stiffness levels for the adhesive were performed. From the numerical analysis, it could be concluded t...
Industrial and academic partners from the Netherlands realized the world’s first 3D concrete prin... more Industrial and academic partners from the Netherlands realized the world’s first 3D concrete printed bicycle bridge. Certification safe use in practice was obtained through the concept of “Design by Testing”. Innovative reinforcement concepts were applied to guarantee safe failure behaviour. This paper discusses the design, testing, manufacturing and assembling of the bridge.
The application of new Computer Aided Manufacturing (CAM), digital fabrication and additive manuf... more 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 l...
Case study projects based on Digitally Fabricated Concrete (DFC) are presented in an increasing p... more Case study projects based on Digitally Fabricated Concrete (DFC) are presented in an increasing pace around the globe. Generally, though, it is not reported what structural requirements (if any) these structures meet and how compliance to these requirements was established. Published material research is often not connected to the presented case studies, and even when it is, it is not necessarily obvious their small scale results can be applied to full scale structures as some scale effects should be anticipated. Caution is required as DFC related material tests are still under development and scale effects in DFC have hardly been studied. Therefore, it is recommendable to perform large scale testing, in the range of 1:5 to 1:1, if DFC is applied to actual use structures. This paper presents such testing for two projects, a pavilion in Denmark (not realized) and a bridge in the Netherlands (realized). In both cases, elements printed with the 3D Concrete Printing facility of the Eindhoven University of Technology were intended for actual load bearing performance. The conservative designs past the test requirements, but nevertheless some important findings with regard to element manufacturing and structural behaviour were experienced. It is concluded that large scale testing remains advisable for DFC structures as long as not all relevant aspects of the technology are quantitatively understood, at least when new concepts are being applied.
High Tech Concrete: Where Technology and Engineering Meet, 2017
Additive manufacturing and 3D printing are rapidly developing digital fabrication techniques (Lu ... more Additive manufacturing and 3D printing are rapidly developing digital fabrication techniques (Lu et al. 2015). After the first steps in small scale printing of metals (Frazier 2014) and plastics (Gibson et al. 2014) have been made, research from various groups around the world is now also focusing on large scale printing in concrete (Lim et al. 2012) and making this technology more suitable for the construction scale. The potential of using this technology is that it will be possible to create complex and/or customised concrete designs with the expectation that the costs will be low and the construction speeds will be high. Additionally, this new technology will provide opportunities to create more efficient structures. Structures can already be optimised in the early stages of the design for weight and structural performance, but the resulting optimised structures are often difficult to manufacture due to the resulting geometry of the design. Additive manufacturing can address this issue without high costs for moulds and labour.
The lack of available reinforcement methods suitable for extrusion-based 3D concrete printing is ... more The lack of available reinforcement methods suitable for extrusion-based 3D concrete printing is well known. Because conventional methods using pre-placed steel bars are incompatible with this manufacturing method, several alternatives are under development. This paper introduces a novel reinforcement application method, based on screwing. Contrary to placement methods based on pushing, i.e. only a translational movement, the combination of translation and rotation inherent in the screwing motion, allows a practically void-free mechanical interlock with which a high level of bond can be attained. The concept makes use of the fact that the print mortar is still highly pliant for some time after deposition, allowing screws to be inserted without fracturing the concrete. The translational-rotational movement needs to be externally controlled, as the material at the early age does not provide sufficient resistance to pull in the screw on application of the rotation. Pull-out tests from printed and cast samples and 3-point bending tests on printed specimens showed a high bond strength and thus underline the feasibility of this concept.
1= glass structure 2= annealed glass 3= failure behaviour 4= design stress Abstract An experiment... more 1= glass structure 2= annealed glass 3= failure behaviour 4= design stress Abstract An experimental transparent pavilion of 9 x 9 x 3.6 m3 has been designed. It combines various innovative concepts like stainless steel reinforced glass beams, resin laminated glass columns, acrylic joints and glass façade elements with glued on fins. However, it's most distinctive feature is the fact that none of the glass is heat-strengthened or tempered. This is part of a revolutionary safety concept stating that failure behaviour similar to that of reinforced concrete is obtainable and desirable for glass structures. This concept is formulated and it's consequences for the structural design of the pavilion are explained. Furthermore, several innovations in the design possibilities of transparent structures are presented.
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