Caitlin Mueller

Robotics-Enabled Stress Line Additive Manufacturing

This paper presents a new robotic additive manufacturing (AM) framework for fabricating 2.5D surface designs to add material explicitly along principal stress trajectories. AM technologies, such as fused deposition modelling (FDM), are typically based on processes that lead to anisotropic products with strength behaviour that varies according to filament orientation; this limits their application in both design prototypes and end-use parts and products. Since stress lines are curves that indicate the optimal paths of material continuity for a given design boundary, the proposed stress-line based oriented material deposition opens new possibilities for structurally-performative and geometrically-complex AM, which is supported here by fabrication and structural load testing results. Called stress line additive manufacturing (SLAM), the proposed method achieves an integrated workflow that synthesizes parametric design, structural optimization, robotic computation, and fabrication.

Funicularity through External Posttensioning: Design Philosophy and Computational Tool

AbstractFunicular geometries, which follow the idealized shapes of hanging chains under a given loading, are recognized as materially efficient structural solutions because they exhibit no bending under design loading, usually self-weight. However, there are circumstances in which nonstructural conditions make a funicular geometry difficult or impossible. This paper presents a new design philosophy, based on graphic statics, that shows how bending moments in a nonfunicular two-dimensional curved geometry can be eliminated by adding forces through an external posttensioning system. An interactive parametric tool is introduced for finding the layout of a posttensioning tendon for any structural geometry. The effectiveness of this approach is shown with several new design proposals.

Automatic generation of diverse equilibrium structures through shape grammars and graphic statics

This article presents a computational design methodology that integrates generative (architectural) and analytical (engineering) procedures into a simultaneous design process. By combining shape grammars and graphic statics, the proposed methodology enables the following: (1) rapid generation of diverse, yet statically equilibrated discrete structures; (2) exploration of various design alternatives without any biases toward pre-existing typologies; (3) customization of the framework for unique formulations of design problems and a wide range of applications; and (4) intuitive, bidirectional interaction between the form and forces of the structure through reciprocal diagrams. Design tests presented in this article illustrate the creative potential of the proposed approach and demonstrate the possibility for unbiased explorations of richer and broader design spaces during early stages of design, with much more trial and less error.

Modelling with Forces: Grammar-Based Graphic Statics for Diverse Architectural Structures

Most architectural modelling software provides the user with geometric freedom in absence of performance, while most engineering software mandates pre-determined forms before it can perform any numerical analysis. This trial-and-error process is not only time intensive, but it also hinders free exploration beyond standard designs. This paper proposes a new structural design methodology that integrates the generative (architectural) and the analytical (engineering) procedures into a simultaneous design process, by combining shape grammars and graphic statics. Design tests presented will demonstrate the applicability of this new methodology to various engineering design problems, and demonstrate how the user can explore diverse and unexpected structural alternatives to conventional solutions.

Using 3D direct manipulation for real-time structural design exploration

Before a new structure can be built, it must be designed. This design phase is a very important step in the building process. The total cost of the structure and its structural performance are largely dependent on the structural design process. The impact of decisions on the design process is initially high and declines as the design matures. However, few computational tools are available for the conceptual design phase; thus, an opportunity exists to create such tools. In the conventional workflow, the architect uses geometric modeling tools and the engineer uses structural analysis tools in sequential steps. Parametric modeling tools represent an improvement to this workflow, as structural analysis plug-ins are available. This allows the architect or engineer to receive structural feedback at an earlier stage, but still as a sequential step to the geometric modeling. The present work aims to improve this workflow by integrating structural feedback with geometric modeling.The user interfaces of conceptual design tools should be interactive and agile enough to follow the designer’s iterative workflow. Direct manipulation involves human-computer interaction, which enables an interactive user interface. In this user interface style, users can directly manipulate on-screen objects using real-world metaphors, which engages the users with their task and encourages further explorations. This is achieved by reducing the perceptual and cognitive resources required to understand and use the interface. New technologies have opened up the possibility of creating new design tools that make use of very direct manipulation. This possibility is further explored in this thesis through the development of two such applications. The first application makes use of multi-touch tablets. The multi-touch interface has literally closed the gap between humans and computers, enabling very direct manipulation interactions with two-dimensional user interfaces. The developed application is an interactive conceptual design tool with real-time structural feedback that allows the user to quickly input and modify structural models through the use of gestures. The second application extends these concepts and ideas into a three-dimensional user interface using an input device named the Leap Motion Controller.

A methodology for auto-calibrating urban building energy models using surrogate modeling techniques

Owners of large building portfolios such as university campuses have long relied on building energy models to predict potential energy savings from various efficiency upgrades. Traditional calibration procedures for individual building model are time intensive and require specially trained personnel, making their applications to campuses with hundreds of buildings prohibitive. Recently proposed automatic calibration techniques reduce the manual effort during calibration but require hundreds of thousands of energy simulations which increase their cost. To reduce the computational effort of these methods, this paper proposes a methodology that uses a data-driven approximation technique. Instead of brute-force simulations using detailed engineering models, this study employs statistical surrogate models with an optimization algorithm to estimate properties of unknown building parameters. Results demonstrate that when envelope information is available, this workflow yields sufficiently accurate estimates of hard to observe building characteristics, about 500 times faster than traditional approaches.

Graphic statics and interactive optimization for engineering education

Although conventional structural analysis software is widely used by practicing engineers, its pedagogical value for students is limited, especially in design applications. Nevertheless, there is an established value in students exploring engineering problems through computational means. This paper presents alternative computational techniques and tools that are effective improvements upon structural analysis software in the university classroom. The first set focuses on graphic statics. The second involves interactive evolutionary optimization. The paper provides feedback about their effective implementation in classrooms and demonstrates how the new tools can continue to be used by students beyond the classroom, to expand explorative opportunities for conceptual structural design in practice.

Robotic Extrusion of Architectural Structures with Nonstandard Topology

This paper presents a fast and flexible method for robotic extrusion (or spatial 3D printing) of designs made of linear elements that are connected in nonstandard, irregular, and complex topologies. Nonstandard topology has considerable potential in design, both for visual effect and material efficiency, but usually presents serious challenges for robotic assembly since repeating motions cannot be used. Powered by a new automatic motion planning framework called Choreo, this paper’s robotic extrusion process avoids human intervention for steps that are typically arduous and tedious in architectural robotics projects. Specifically, the assembly sequence, end-effector pose, joint configuration, and transition trajectory are all generated automatically using state-of-the-art, open-source planning algorithms developed in the broader robotics community. Three case studies with topologies produced by structural optimization and generative design techniques are presented to demonstrate the potential of this approach.

Structural Patterning of Surfaces

This research introduces new computational workflows to design structural patterns on surfaces for architecture. Developed for design but rooted in the rigor of structural optimization, the strategies are aimed at maximizing structural performance, as measured by weight or stiffness, while offering a diversity of solutions responding to non-structural priorities. Structural patterns are important because they create meaningful difference on an otherwise homogeneous architectural surface; by introducing thickness, ribs, or voids, patterns accumulate material where it is most useful for structural or other purposes. Furthermore, structural patterning with greater complexity is enabled by the recent advancements in digital fabrication. However, designers currently lack systematic, rigorous approaches to explore structural patterns in a generalized manner. The workflows presented here address this issue with a method built on recent developments in computational design modelling, including isogeometric analysis, a NURBS-based finite element method. Most previous work simply maps patterns onto a surface based on stress magnitudes in its continuous, unpatterned state, thus neglecting how the introduction of holes interrupts the flow of forces in the structure. In contrast, this work uses a new trimmed surface analysis algorithm developed by the authors to model force flow in patterned surfaces with greater fidelity. Specifically, the proposed framework includes two interrelated computational modelling schemes. The first one operates on a human-designed topology pre-populated with an input cell shape and position. An optimization algorithm then improves the design through simple geometric operations in the parametric space applied independently on each cell or globally using control surfaces. The second modelling scheme starts with an untrimmed surface design and successively optimizes its shape and introduces new cells. Both optimization systems are flexible and can incorporate constraints and new geometric rules.

A comparison of two algorithms for the simulation of bending-active structures

Bending-active structures, made from elastically bent materials such as fiberglass rods, offer exciting opportunities in architecture because of their broad formal palette and ease of construction. While they have been relevant since Frei Otto’s Mannheim Multihalle (1974), recent computational developments that help simulate active-bending processes have renewed interest in them. Such tools are important because they can replace time-consuming and imprecise physical modeling processes. However, physically meaningful simulations, using real materials and full scale, are difficult to create, and there are no good mechanisms to reveal when a simulation is inaccurate. This article offers a conceptual and numerical study of two popular contemporary algorithms for simulations of bending-active structures, mainly through a comparison of their results on the planar elastica. We then offer guidelines on best practice modeling settings and demonstrate possibilities and pitfalls through an architectural-scale case study.