Patrick Bischof


Last Name

Bischof

First Name

Patrick

ORCID

0000-0003-3032-5482

Organisational unit

09469 - Kaufmann, Walter / Kaufmann, Walter

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2017 - 201912020 - 202313
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Publications 1 - 10 of 14
  • Identifying Levers for Mass Market Penetration of Digital Fabrication
    Item type: Conference Paper
    Bischof, Patrick; Mata Falcón, Jaime; Kaufmann, Walter (2021)
    fib Symposium Proceedings ~ Concrete Structures: New Trends for Eco-Efficiency and Performance, Proceedings of the fib Symposium 2021
    The construction industry produces buildings and infrastructure and, hence, satisfies basic needs of modern society. It provides a considerable portion of total value added and worldwide jobs. At the same time, it is responsible for more than 11% of CO2 energy-related carbon dioxide (CO2) emis-sions worldwide. Digital concrete fabrication is a young, yet already broad research discipline which brings about potential for the necessary reduction of the ecological impact and for further industrial-isation of the construction industry, while being compatible with the specific requirements of flexi-bility and individuality. Still, it has not succeeded to penetrate the mass-market, largely due to lack-ing competiveness and compliance with structural integrity requirements. The present contribution comprehensively considers features of conventional construction processes to identify benefits when using digital concrete fabrication. Thereby, it addresses not only a complete substitution of conven-tional construction methods, but also solutions taking advantages of the synergic combination of traditional and novel technologies. It assesses traditional construction methods (in-situ construction and prefabricated construction) and clusters their features in order to elaborate their strengths and persistent challenges. Following a customised review on the digital fabrication methods, it identifies some new levers and opportunities for mass-market penetration of digital concrete fabrication tech-nologies in structural and civil engineering construction works.
  • Risk-Based Design for Fire Spalling of Concrete
    Item type: Conference Paper
    Borgogno, Walter; Bischof, Patrick; Kaufmann, Walter (2017)
    Material science has not yet succeeded to fully explain the mechanics of explosive fire spalling. What is missing is a clear definition of the parameters governing explosive spalling to what extent. As a result, the fully material based instructions of EN 1992-1-2 [1] do often not allow for satisfactory identification of explosive spalling issues and to handle explosive spalling in buildings. Nevertheless, no global building failure due to concrete spalling under fire conditions has been observed to the authors’ knowledge. This document presents a general risk-based spalling design approach suitable for application in engineering practice. The approach takes both material behaviour and structural behaviour into account by means of spalling risk classes (SRC). For each SRC, methods for both spalling design and structural ultimate limit state fire design are provided. The different design methods are subdivided into different levels of approximation. The more severe the consequences of explosive spalling are the more precise design methods must be used. The aim of the proposed method is to draw attention in design to the parts of the building where a high probability of spalling actually results in more severe consequences or higher risks, respectively. On the other hand, the use of the proposed method allows avoiding extensive discussions about potential spalling issues for uncritical structural elements. Furthermore, the proposed method provides a means to structural engineers for handling explosive spalling not only by specifying sometimes rather unreliable material properties, but also by accounting for a robust design.
  • New structural engineering possibilities of digital fabrication towards leaner concrete structures
    Item type: Presentation
    Mata Falcón, Jaime; Lee, Minu; Gebhard, Lukas; et al. (2022)
    The design possibilities of concrete structures are typically tightly constrained by the high costs and material waste of formworks and reinforcement for producing non-conventional shapes. Digital fabrication technologies aim at producing structures with increased degrees of geometrical freedom at little extra cost and avoiding material waste. This might allow (i) revisiting abandoned structural typologies (e.g. shells, folded roofs, ribbed or mushroom slabs) and (ii) exploring new concepts towards leaner construction. In this lunch talk, researchers from the Group of Concrete Structures and Bridge design at ETH Zurich will present recent structural engineering developments within the domain of Digital Fabrication with Concrete, making use of technologies such as 3D concrete printing, knitted textile reinforcement, robotic reinforcement assemblies and 3D formwork printing.
  • Pre-installed Reinforcement for 3D Concrete Printing
    Item type: Conference Paper
    Gebhard, Lukas; Bischof, Patrick; Anton, Ana; et al. (2022)
    RILEM Bookseries ~ Third RILEM International Conference on Concrete and Digital Fabrication
    Providing reinforcement is essential for the structural integrity of concrete elements and for safely handling, transporting, and assembling prefabricated concrete parts. However, the integration of reinforcement is a persisting challenge in 3D concrete printing with extruded concrete. This paper presents a production process consisting of 3D printing around pre-installed reinforcement. The reinforcement is composed of conventional reinforcing steel bars, which can be pre-assembled in cages independently of casting, boosting the specialisation and efficiency in production. This approach was used to produce a 3.4 m span T-beam with optimised topology, consisting of three segments connected with matching surfaces. The beam segments were printed upside down, with an open web on top of the flange. Each segment featured reinforcing steel installed in the flange and web. After printing and assembling the segments, a conventional reinforcing bar was inserted in the web as bending reinforcement and grouted subsequently. The structural performance was assessed in a six-point bending test. The fabrication and structural testing of this case study beam showed that pre-installed reinforcement imposes several challenges to the extruder precision, the precision of the bent reinforcement, and – if applied – the casting after printing.
  • Assessment of parameters influencing the behavior of statically indeterminate reinforced concrete slabs and beams under fire conditions
    Item type: Journal Article
    Bischof, Patrick; Morf, Urias; Kaufmann, Walter (2023)
    Structural Concrete
    This paper investigates the effect of material properties, boundary conditions, and related modeling and design uncertainties on the fire behavior of statically indeterminate reinforced concrete beams and slabs by means of a parametric study based on a comprehensive model. This model uses material properties specified by EN 1992-1-2, complemented by considerations concerning the biaxial compressive strength of concrete, strain hardening and limitations of the ultimate strain of reinforcement, as well as tension stiffening. The parametric study identifies and explains the most influential parameters governing the fire behavior of statically indeterminate reinforced concrete beams and slabs. The implementation and generalization of these parameters are evaluated and compared to current design rules in EN 1992-1-2 derived from the evaluation of experimental testing and real fire cases. Overall, the detailing rules given in EN 1992-1-2 are found to be reasonably safe, and they can be easily used for practical applications. Furthermore, the results of the study indicate that model predictions for the studied statically indeterminate systems are subject to considerable uncertainty because (i) information on the used material is possibly incomplete and (ii) the models given in design codes do not (or only insufficiently) cover all relevant aspects of the thermo-mechanical behavior. Specifically, the concrete aggregate type with its corresponding thermal expansion, the strain hardening properties of the reinforcement and tension stiffening with its detrimental effect on the ductility of the tension chord may affect the rating across several standard fire resistance times of statically indeterminate reinforced concrete members subjected to bending.
  • Digitally Fabricated Keyed Concrete Connections
    Item type: Conference Paper
    Bischof, Patrick; Mata Falcón, Jaime; Burger, Joris Jan; et al. (2022)
    RILEM Bookseries ~ Third RILEM International Conference on Concrete and Digital Fabrication
    Most current technologies in digital fabrication with concrete (DFC) rely on controlled environmental conditions and, thus, have been used in prefabricated construction. Prefabricated reinforced concrete elements produced in factories need assembly and connection on-site. Using DFC for producing tailor-made geometries and applying surface roughness generates new possibilities for the design of connections. DFC enables (i) fabricating dry connections, for example, by using exact formworking or milling processes, and (ii) the relatively straightforward preparation of rough construction joints, for example, by using extrusion processes. In a recent study, a series of different specimens incorporating connections were tested using deformation-controlled push-off tests. This contribution presents the experimental campaign including design, preparation and test results employing keyed connections produced with the Eggshell technology, a fabrication process using 3D printed thin plastic formwork.
  • Fostering innovative and sustainable mass-market construction using digital fabrication with concrete
    Item type: Journal Article
    Bischof, Patrick; Mata Falcón, Jaime; Kaufmann, Walter (2022)
    Cement and Concrete Research
    The construction industry produces buildings and infrastructure. These construction works are typically immobile and customised, and must meet many criteria to provide value to modern society: structural safety, durability, serviceability, aesthetics and integration, environmental sustainability and construction efficiency. Accordingly, traditional construction methods, along with the resulting construction works, have been adapted to comply with these multifaceted requirements for more than a century. However, the construction industry has a considerable environmental impact, with reinforced concrete as its primary driver due to its extensive use, and will be facing an ever-increasing responsibility to tackle climate neutrality in the upcoming years. Digital fabrication with concrete is a young yet already broad discipline that brings about the potential for the necessary reduction of the environmental impact and further industrialisation of the construction industry while being compatible with the multifaceted requirements for construction works. Still, it has not penetrated the construction mass market, which is paramount for making a significant difference towards improving the environmental impact of the construction industry. The present study tackles this issue by (i) assessing traditional construction and digital fabrication on a value-driven basis, identifying and summarising their inherent strengths and challenges, and (ii) proposing a value-driven ideation process to identify relevant mass-market levers of digital fabrication in the construction industry. The presented methodology indicates two exemplary applications of how traditional construction and digital fabrication processes can be combined to tackle the persistent environmental sustainability challenges.
  • Rethinking Structural Concrete for Digital Fabrication
    Item type: Doctoral Thesis
    Bischof, Patrick (2023)
    Construction works are typically large, immobile and customised, and must meet many criteria to provide value to modern society: structural safety, durability, serviceability, aesthetics and integration, environmental sustainability and construction effciency. Traditional construction methods have been adapted to comply with these multifaceted requirements for more than a century. However, the construction industry has a considerable environmental impact, with reinforced concrete as the primary driver due to its extensive use, and will be facing an ever-increasing responsibility to tackle climate neutrality in the upcoming years. Digital fabrication with concrete (DFC) is a young yet already broad discipline that brings about the potential for reducing the environmental impact and further industrialising of the construction industry. Still, it has not penetrated the construction mass market, which is paramount for having a signifcant impact. The frst part of the present thesis tackles this issue by (i) assessing traditional construction and digital fabrication on a value-driven basis, identifying and summarising their inherent strengths and challenges, and (ii) proposing an ideation process to identify relevant mass-market levers of digital fabrication in the construction industry. The second part of the thesis investigates two exemplary applications conceived within this ideation process: digitally fabricated structural connections and weak interfaces for reducing minimum reinforcement. Connections of structural members are a persistent challenge for traditional reinforced concrete construction and even more so for DFC to meet the promise of delivering geometrically optimised structures with minimised environmental impact. At the same time, DFC opens up new approaches for producing connections, such as for transferring shear forces across interfaces with tailored geometries. An experimental exploration of such shear joints was performed using a push-off test setup to showcase the feasibility of DFC for connections. The programme included the design, fabrication and structural testing of joints using the technology Eggshell to 3D print the formwork, providing (i) unreinforced and reinforced construction joints with varying joint surface texture and (ii) digitally fabricated dry keyed joints with varying key geometry. The joints were produced using set-on-demand concrete with a relatively small maximum aggregate size of 4 mm, as typically applied in DFC. The experimental campaign included thorough instrumentation (i) proving the high geometric accuracy of the produced joint interfaces and (ii) allowing to study the effciency of the varying surface textures. Despite the small aggregate size used, the shear transfer capacity of all tested joints met or even outperformed the requirements defned in pertinent design codes. Crack initiators can be used to diminish the minimum reinforcement for members subjected to imposed deformations and environmental exposure as they reduce the crack spacing and width when arranged close enough. While crack initiators in conventional concrete construction are cumbersome to provide (e.g. by construction joints or taperings), they are inherent to layered extrusion processes with many DFC technologies: the tensile strength is typically reduced locally in the interfaces between layers. An analytical method based on the Tension Chord Model was developed to (i) account for the local strength reduction and (ii) predict the effect of weak interfaces on the expected crack spacing and width. As a key fnding, the model predicts a reduction of the required minimum reinforcement ratio proportional to the locally decreased concrete tensile strength for a specifed maximum crack width requirement under imposed deformations. An experimental campaign on fve layered and three reference tension ties confrmed the clearly positive impact of weak interfaces on crack spacings and widths. These two applications studied in detail served as prototypes to indicate how traditional construction and digital fabrication processes can be combined to tackle the persistent environmental sustainability challenges.
  • Digitally fabricated weak interfaces to reduce minimum reinforcement in concrete structures
    Item type: Journal Article
    Bischof, Patrick; Mata Falcón, Jaime; Ammann, Rebecca; et al. (2023)
    Structural Concrete
    Crack initiators in reinforced concrete structures can facilitate fulfilling the serviceability requirements. They can be used as a design parameter to diminish the minimum reinforcement for members subject to imposed deformation and exposed to the environment as they reduce the crack spacing and width when arranged close enough. While crack initiators in conventional concrete construction are cumbersome to provide (e.g., by construction joints or taperings), they are inherent to layered extrusion processes with digital fabrication technologies: the tensile strength is typically reduced locally in interfaces between layers. Rather than trying to avoid these weak interfaces, this paper discusses the potential of taking advantage of them to act as crack initiators reducing the minimum reinforcement content. A tension chord-based model is developed to (i) account for the local strength reduction and (ii) predict the effect of weak interfaces on the expected crack spacing and width. As a key finding, the model predicts a reduction of the required minimum reinforcement ratio proportional to the locally decreased concrete tensile strength for a specified maximum crack width requirement under imposed deformations. An experimental campaign on five layered and three reference tension ties confirmed the clearly positive impact of weak interfaces on crack spacings and widths.
  • Column-Slab Interfaces for 3D Concrete Printing
    Item type: Conference Paper
    Anton, Ana-Maria; Skevaki, Eleni; Bischof, Patrick; et al. (2022)
    Hybrids & Haecceities: Proceedings of the 42nd Annual Conference of the Association for Computer Aided Design in Architecture
    3D Concrete Printing (3DCP) currently dominates the scene of digital fabrication with concrete. 3DCP can be utilized on-site or in prefabrication setups. While prefabrication with 3DCP allows for more complex construction elements, it also requires the design for connections and assembly. In the context of prefabrication using 3DCP, this paper illustrates the state of research in the design, construction, and assembly of 3D printed components. It proposes segmentation and fabrication strategies to produce horizontal and vertical structural members of a column-slab building system following the typology of mushroom slabs. The design proposal was experimen tally investigated with two prototypes. Each prototype consists of five elements assembled into 1:1 scale, column-slab connection demonstrators. These prototypes were robotically fabricated using a three-component 3DCP material system and a hardware setup enhanced by a sensor system that supplies online fabrication data for process monitoring and quality control. Based on 3D scans, the recorded fabrication data set is benchmarked against the initial design models to assess the accuracy of the printed elements. Conclusions about process robustness and prefabrication quality of the components are drawn, focusing on the interfaces between components. Finally, mitigation strategies are suggested to enhance the accuracy of the proposed fabrication method.
Publications 1 - 10 of 14