In conversation with simulation: The application of numerical simulation to the design of structural nodal connections

Licentiate thesis, 2020

The thesis explores methods for integration of structural analysis, design and production in a digital design environment. The somewhat ambiguous title implies the ambition to make such integration in relation to the explorative phase of the design process which is described by Donald Schön as having a conversational character. A conversation between the designer and the representation by the means of the tool. The tool is in this context a simulation and instead of exploring the potential of automatic optimisation, the simulation is used for designer driven exploration.

The aim of the thesis is to give an overview of how this type of integration is currently being approached and to contribute with new tools and methods in that pursuit. The motivation behind the work is to lower the threshold for the application of structural analysis in early-stage design, with an ambition of architectural qualities and resource efficiency in mind.

An overview of the historical context is portrayed with broad brush strokes, followed by a more precise account of the mathematical and physical context, which is complemented by an attempt to describe how our tools and roles tend to interplay in the composition of the design process. Methods such as the finite element method, isogeometric analysis, smoothed particle hydrodynamics and peridynamics, including their related geometrical representations are introduced in relation to this context. A variety of production techniques are also discussed in relation to material mechanical properties for conventional building materials such as steel, concrete and wood.

The method development is approached through the use of numerical and physical experiments which are applied for design of material-efficient structural components, with a particular design process perspective. The nodal connection is chosen as an application because it combines geometrical and structural complexity in an element that is of crucial importance for a holistic spatial setting, while often being produced in a material inefficient way, with poor attention to detail.

The three articles that are included follow a trajectory from large to small, from the holistic to the particular. The first article is a description of the computational design work with the roof for the new international airport of Mexico City. The second article aims to address one of the challenges that were faced in that project with material inefficiency for nodal connections, with a critical perspective on optimisation. The final article presents an extension/modification for the peridynamics theory enabling variable particle sizes and an irregular particle distribution through the introduction of a concept called force flux density. The development is motivated by limitations found in the present theory through numerical experiments. The method enables simulation of phenomena such as brittle fracture, for which correlation with Griffith's theory of fracture is shown.

Further work includes an extension of the force flux method from 2D to 3D, including calibration of material a model for 3D printed steel. Other possibilities involve the exploration of how such a method can adapt to the various stages of the design process, where requirements of accuracy, speed and interactivity will vary.