Freek Bos

Freek Bos
Technische Universität München | TUM · School of Engineering and Design

Doctor of Engineering

About

102
Publications
49,673
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3,999
Citations
Citations since 2016
56 Research Items
3794 Citations
201620172018201920202021202202004006008001,0001,2001,400
201620172018201920202021202202004006008001,0001,2001,400
201620172018201920202021202202004006008001,0001,2001,400
201620172018201920202021202202004006008001,0001,2001,400

Publications

Publications (102)
Article
This article focuses on the specifics in characterizing the properties of additively manufactured, cement-based materials in their hardening and hardened states. Such characterization is required for the material development, structural design, and quality control of both printable material and 3D-printed elements. The related challenges are associ...
Article
Welcome at Challenging Glass 8!We gradually emerge from two difficult years of the covid-19 pandemic raging through the world in waves of constantly changing intensities. The associated uncertainties really put the ‘challenging’ into Challenging Glass this time. Still, some of our peers are not able to join us in Ghent, and they will be sorely miss...
Article
Full-text available
Extrusion-based 3D Concrete Printing (3DCP) is rapidly gaining popularity in the construction industry. Trial projects are now being realized at an increasing rate around the world to test the viability of the technology against real-world requirements. This step, from the ‘simple’ deposition of filaments of self-stable concrete to its application...
Chapter
Previous research has shown that the material properties of a three-dimensional printed strain hardening cementitious composite (3DP-SHCC) can significantly vary, depending on the printing system with which it is produced. However, limited research has been performed on the reproducibility of hardened mechanical properties under identical printing...
Article
Full-text available
Since the advent of three-dimensional concrete printing (3DCP), several studies have shown the potential of strain hardening cementitious composites (SHCC) as a self-reinforcing printable mortar. However, only a few papers focus on achieving sufficient buildability when developing printable SHCC. This study investigates the role of the particle siz...
Article
Full-text available
In this work, a framework for large-scale structural applications of 3D printed concrete is presented. The steps in this framework, consisting of a design phase, testing phase and manufactur-ing phase, towards a final output were presented and discussed theoretically. The framework was then applied to the case of a 29 m 3D printed bridge, construct...
Chapter
The comprehending of the processes’ physics is a prerequisite for the purposeful design and optimization of digital fabrication systems, as well as their efficient and robust process control. This chapter presents an overview of the underlying physics relevant to an understanding of the processing of cement-based materials during various production...
Chapter
Digital fabrication with cementitious materials is a rapidly growing field of research in which the evolution of strength during the various processes, such as 3D printing, is the key controlling parameter. The strength evolves over multiple orders of magnitude during the process, and thus, it is essential to properly characterize the strength evol...
Chapter
The form freedom enabled by digital fabrication with concrete technologies provides advantages for a wide range of concrete based objects, from architectural to structural elements. The current chapter focuses on the specifics of structural design and engineering of DFC with emphasis on those technologies based on Additive Manufacturing with extrus...
Chapter
The need for methods for forming concrete has existed for as long as concrete has been used in constructing the built environment. Creating flat, rectilinear formers have traditionally been the cost and time efficient default for the majority of applications. The desire for greater design freedom and the drive to automate construction manufacturing...
Chapter
Full-text available
In structural applications reinforcement is required to achieve sufficient tensile strength and ductility. While several concepts are being developed to achieve this in 3D concrete printing, no generic method has been established yet and as a result all built objects are solved on a case-by-case basis. In this study one of the potential solutions,...
Article
Full-text available
The incompatibility of 3D concrete printing (3DCP) with conventional reinforcement methods is well known. Recently, solutions have suggested the insertion of helical reinforcement rods through a screwing motion into the freshly printed material. The current study focuses on the bond properties of such reinforcement and its relation to placement tim...
Article
Full-text available
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 st...
Article
Full-text available
Both industry and academia are rapidly developing processes, materials, and projects to explore the potential of extrusion-layering additive manufacturing of cementitious materials, generally known as 3D concrete printing (3DCP). Because the lack of supportive formwork makes objects prone to failure during printing, a key aspect remains the so-call...
Article
In this chapter, we review how the brittle nature of glass requires specific attention in the design, manufacturing, and construction of point‐fitted glass; glass floors and stairs; balustrades and façade fins; glass roofs and walls. These applications in buildings, which go far beyond the traditional framed glazing, are all grouped under the term...
Article
This article offers a comprehensive, systematic overview of the existing solutions for integrating reinforcement in digital concrete technologies with particular emphasis on Additive Manufacturing (AM) with concrete, also called 3D concrete printing (3DCP). While the functionalities of various types of reinforcement are briefly addressed, the major...
Article
Full-text available
Digital Fabrication with Concrete (DFC) encompasses 3D Concrete Printing (3DCP) and many other methods of production. DFC is emerging from an era of invention and demonstration to one where the merits of one principle over another needs to be quantified systematically. DFC technologies vary in characteristics, complexity and maturity which hampers...
Chapter
Full-text available
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...
Chapter
Full-text available
Over the past few years, several studies have shown the potential of three-dimensional concrete printing (3DCP) for applications in building and civil engineering. However, only a few studies have compared the properties of the fresh printing material and the quality of the printed elements from different printing facilities. Variations in the manu...
Chapter
During the summer semester 2018–2019, a 3D concrete printed (3DCP) pavilion consisting of 47 unique free form parts was realized in the central square of the engineering campus of the University of Innsbruck. In a period of just 11 weeks, it was designed, engineered, manufactured, and assembled on-site to provide an attractive meeting space for stu...
Conference Paper
Full-text available
3D Concrete Printing (3DCP) is being used for off-site manufacture of many elements found in the built environment, ranging from furniture to bridges. The advantage of these methods is the value added through greater geometrical freedom because a mould is not needed to create the form. In recent years, research has focused on material properties bo...
Chapter
The use of high strength steel cables directly entrained into printed concrete during the printing process, has previously been introduced as a method to provide reinforcement to objects being manufactured through a layer-extrusion based 3D concrete printing process. The bond between the cable and the cementitious mortar is a crucial parameter for...
Chapter
Additive manufacturing (AM) or 3D printing is a rapid prototyping process that has captured the attention of architects and designers worldwide in the last few years. Multiple research groups and commercial entities are exploring different areas of 3D concrete printing (3DCP) with one of the main topics being the potential to improve the design fre...
Article
Digital fabrication technologies utilizing concrete (DFC) have recently enabled form freedom for the production of a variety of concrete-made objects having mainly architectural and aesthetic functions. Structural elements or civil/building structures made by DFC demonstrate a high engineering potential, mainly for tailoring the final shape while o...
Article
While interest in 3D printing of concrete (3DCP) and structures has been growing, a major obstacle for implementation of 3DP construction method is the need for steel reinforcement and the challenges this presents to the 3DP process. Engineered Cementitious Composites (ECC), also known as Strain-hardening Cement-based Composites (SHCC), hold promis...
Article
Full-text available
Extrusion based additive manufacturing of cementitious materials has demonstrated strong potential to become widely used in the construction industry. However, the use of this technique in practice is conditioned by a feasible solution to implement reinforcement in such automated process. One of the most successful ductile materials in civil engine...
Article
Full-text available
The rapid development of additive manufacturing of cementitious materials has enabled the emergence of a new design paradigm, namely functional grading of material properties by location. Target performance parameters could be material weight and insulation value or (particularly important) ductility. A generic concept to achieve this, is through t...
Book
This book gathers peer-reviewed contributions presented at the 2nd RILEM International Conference on Concrete and Digital Fabrication (Digital Concrete), held online and hosted by the Eindhoven University of Technology, the Netherlands from 6-9 July 2020. Focusing on additive and automated manufacturing technologies for the fabrication of cementiti...
Conference Paper
Due to the lack of formwork, a key issue in the novel technology of filament-based 3D concrete printing (3DCP) is the ‘buildability’: the capacity of the deposited dormant material to support itself during the print process. Since the strength and stiffness development of fresh concrete is determined by chemical and physical processes, it may be ex...
Article
Digital fabrication techniques with concrete and cementitious materials have seen a large amount of research and industrial activity recently, with industrialization of techniques such as 3D printing becoming more of a reality. The potential to revolutionize construction is real, not only through reducing costs, but also bringing more sustainabilit...
Article
In 3D concrete printing processes, two competing modes of failure are distinguished: material failure by plastic yielding, and elastic buckling failure through local or global instability. Structural analysis may be performed to assess if, and how, an object may fail during printing. This requires input in the form of transient material properties...
Article
Full-text available
New additive manufacturing methods for cementitious materials hold a high potential to increase automation in the construction industry. However, these methods require new materials to be developed that meet performance requirements related to specific characteristics of the manufacturing process. The appropriate characterization methods of these m...
Article
The technology of 3D Concrete Printing (3DCP) has progressed rapidly over the last years. With the aim to realize both buildings and civil works, the need for reliable mechanical properties of printed concrete grows. As a consequence of the additive manufacturing technique, 3D printed structures may consist of several layers that should exhibit bon...
Chapter
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 st...
Article
Full-text available
With the number of 3D printed concrete structures rapidly increasing, the demand for concepts that allow for robust and ductile printed objects becomes increasingly pressing. An obvious solution strategy is the inclusion of fibers in the printed material. In this study, the effect of adding short straight steel fibers on the failure behaviour of We...
Article
One of the geometrical restrictions associated with printed paste materials such as concrete, is that material must be self-supporting during printing. In this research paper a new methodology for 3D Printing Concrete onto a temporary freeform surface is presented. This is achieved by setting up a workflow for combining a Flexible Mould developed a...
Article
3D printing of concrete and related digital fabrication techniques are enjoying rapid growth. For these technologies to be broadly accepted in structural applications and to be economically competitive, quality control methods of the process will be required. Additive concrete manufacturing processes are sensitive to process settings and conditions...
Article
The fabrication of novel reinforced concrete structures using digital technologies necessarily requires the definition of suitable strategies for reinforcement implementation. The successful integration of existing reinforcement systems, such as steel rebar, rods, wires, fibres or filaments, will indeed allow for printed concrete structures to be d...
Article
Full-text available
The current state of research and development into the additive manufacturing of concrete is poised to become a disruptive technology in the construction industry. Although many academic and industrial institutions have successfully realised full-scale structures, the limitations in the current codes of practice to evaluate their structural integri...
Article
A numerical model was developed to analyse the mechanical behaviour of fresh, 3D printed concrete, in the range of 0 to 90 min after material deposition. The model was based on a time-dependent Mohr-Coulomb failure criterion and linear stress-strain behaviour up to failure. An experimental program, consisting of unconfined uniaxial compression test...
Chapter
Recent years have seen a rapid growth of additive manufacturing methods for concrete construction. A recurring issue associated with these methods, however, is the lack of ductility in the resulting product. In cases this is solved by combining printing with conventional casting and reinforcing techniques. Alternatively, this paper presents first f...
Chapter
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...
Article
Full-text available
The Material Deposition Method (MDM) is enjoying increasing attention as an additive method to create concrete mortar structures characterised by a high degree of form-freedom, a lack of geometrical repetition, and automated construction. Several small-scale structures have been realised around the world, or are under preparation. However, the natu...
Conference Paper
Additive manufacturing and 3D printing are rapidly developing digital fabrication techniques (Lu et al. [10]). After the first developments in small scale printing of metals (Frazier [6]) and plastics (Gibson et al. [7]) have been made, research from various groups around the world is now also focusing on large scale printing in concrete (Lim et al...
Chapter
Full-text available
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. 201...
Article
Additive manufacturing is gaining ground in the construction industry. The potential to improve on current construction methods is significant. One of such methods being explored currently, both in academia and in construction practice, is the additive manufacturing of concrete (AMoC). Albeit a steadily growing number of researchers and private ent...
Conference Paper
The effect of scale on different parameters of the 3D printing of concrete is explored through the design and fabrication of a 3D concrete printed pavilion. This study shows a significant gap exists between what can be generated through computer aided design (CAD) and subsequent computer aided manufacturing (generally based on CNC technology). In r...
Conference Paper
The refurbishment of the Meuse river boulevard in Venlo instigated Scheuten Glass to donate a giant-sized, 6 metre high version of the stacked glass statue the Sphinx, which had originally been made as a 80 cm sculpture to commemorate the city's 650th anniversary back in 1993. Many hurdles had to be taken to, starting with the preliminary feasibili...
Article
Annealed, heat-strengthened and fully tempered SG-laminated reinforced glass beam specimens were subjected to four-point bending tests to investigate the effects of glass type on their structural response. During the test the beams showed linear elastic response until initial glass failure, followed by a significant post-breakage strength and ducti...
Conference Paper
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 ne...
Article
In this paper it will be shown elastic strain energy release is a key parameter for the post-failure resistance of a structural glass element, as it influences both the post-failure compressive capacity through the crack pattern, and the post-failure tensile capacity, through shock loading of the tensile component at initial failure. The complex re...
Article
To generate high-level redundancy for structural glass beams, a novel concept of laminating a metal reinforcement to a structural glass beam has been developed at Delft University of Technology (TU Delft). This concept makes use of the relatively stiff polymer interlayer material SentryGlas (SG) to bond the metal to the glass. However, due to the v...
Conference Paper
Full-text available
The amount of elastic strain energy that is being released upon initial failure of a structural glass element has profound influence on its post-initial failure load bearing capacity. This paper discusses the relevance of this notion to the evaluation of structural glass testing and the consequences it may have for structural glass design. It means...
Conference Paper
Full-text available
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 l...
Article
Full-text available
This paper investigates whether a novel computational sequentially linear analysis (SLA) technique, which is especially developed for modeling brittle material response, is applicable for modeling the structural response of metal reinforced glass beams. To do so, computational SLA results are compared with experimental results of four-point bending...
Article
Die bestehenden Methoden zur Sicherheitsbewertung von Glaskonstruktionen sind unzureichend. Es fehlen identifizierbare Bauteil-Sicherheits-Eigenschaften. Die Folge sind Diskussionen und Unsicherheiten in der Ingenieurpraxis. Ziel der Integrierten Methode für die Sicherheitsbewertung von Glasbauteilen ist die Schaffung objektiver Kriterien für den V...
Article
Full-text available
Glass panes are increasingly being used to the stabilization of one storey buildings by acting as shear walls and thus replacing conventional bracings. This is the case of glass pavilions and some timber or steel frames or facades. The behaviour of such structural systems mainly depends on the stiffness of the connections. This research focuses on...
Article
Full-text available
This paper investigates the possibilities of pultruded glass fibre rods as embedded reinforcement in SentryGlas (SG) laminated glass beams. To do so, a series of pullout tests, to investigate the bond strength of the rods to the laminate, and a series of beam tests, to investigate the post-breakage response of the beams, have been performed. Both t...
Conference Paper
Keywords 1 = Strain Energy 2 = Glass Beam 3 = Failure Behaviour 4 = Post-failure 5 = Reinforced Abstract The failure behaviour of two reinforced glass beam designs has been compared in a four-point bending test. One design featured a slim section with a high moment of inertia and thus relatively low elastic strain energy absorption. The section of...
Conference Paper
A large quantity of glass beams has been subjected to three different test methods based on 4-point bending. Specimens were either tested directly or after having been damaged by a spring-loaded impact device, with or without a simultaneous static load. The specimen variables included the most important commonly available design- and material speci...
Conference Paper
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 w...
Conference Paper
Keywords: 1=reinforced 2=beam 3=SentryGlas 4=interlayer 5=temperature 6=redundancy. Abstract To validate the novel concept of laminating a metal reinforcement to a glass beam using a SentryGlas (SG) interlayer, a series of bending tests has been performed at 23,-20 and 60°C on 1.5 m SG-laminated metal-reinforced glass beams. The beams consisted of...
Article
In the last two decades architectural glass has made an enormous leap from a secondary material to a material that combines structural and cladding roles. The structural role is a new and problematic one. In contrast to most other engineering materials the strength of glass is not a material parameter but a parameter dependent on processing quality...
Article
Full-text available
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...
Conference Paper
Structurally used tubular glass provides stunning possibilities for architectural applications, which have hardly been explored yet. Over the last decade, only a handful of experimental structures have been presented, such as a 3D lattice structure by the University of Stuttgart [1], a tensigrity structure [2] and columns in a pavilion by the TU De...
Conference Paper
For several years the Glass & Transparency research group at Delft University of Technology has been working on safety concepts for glass structures and structural glass components. In contrast with common `safety' approaches, the developed safety concepts do not rely on overdimensioning, but aim at controlled and ductile failure behaviour. Since g...