Achieving Diverse and Competitive Designs Using a Parallel Bi-directional Evolutionary Structural Optimisation Framework
Creators: name: Xiong, Yulin
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 400510
subject: Structural engineering

description: Topology optimisation is increasingly used as a computer-aided design tool. It enables designers to create elegant and efficient structures. The primary goal of topology optimisation is to identify the optimal design that satisfies prescribed requirements for structural performance subject to certain constraints. However, it is often challenging to incorporate various aesthetic considerations or functional requirements due to their complexities and uncertainties. For this reason, it is desirable to have an optimisation approach that can generate diverse solutions for the same loading and boundary conditions, allowing the designer to make selections based on their personal preferences or other requirements. Therefore, this thesis aims to develop automatic design tools that can effectively generate diverse, freeform and optimised solutions, providing architects and structural engineers with multiple choices in their conceptual design phase.

The thesis consists of three main parts. Firstly, recognising the critical importance of computational efficiency in large-scale design problems, the traditional Bi-directional Evolutionary Structural Optimisation (BESO) method is enhanced with modern parallel computing techniques. Several methods are integrated to boost computational efficiency, including the iterative solver, the reanalysis approach, the partial differential equation (PDE)-based filter scheme, and the hard-kill BESO option. The finite element analysis is facilitated by FEniCS, an open-source platform that automates the solution of complex PDEs in a simple implementation. The developed method can efficiently solve the high-resolution topology optimisation problems, serving as the foundation for the remaining two parts of this thesis.

In the second part, two perturbation approaches are integrated into the parallel BESO framework, aiming to create diverse and structurally competitive designs. By applying perturbations to load directions and altering material properties near supports during interim iterations, noise is introduced into the sensitivity analysis, thereby resulting in a variety of solutions. Furthermore, the approaches hold the potential to control the similarity of diverse designs by adjusting the perturbation functions. This component offers a powerful tool for designers to explore the design space, paving the way for innovative design solutions.

In the third part, a three-field BESO method with a variable-radius filter is proposed to further investigate the generation of diverse designs. In this study, both the density of elements and the filter radius are considered variables in the design process. Compared to the second part of this thesis, the size constraints brought by the filter scheme are relaxed, thus enabling the achievement of designs with multiple morphologies. To enhance the range of possible designs, this method includes the use of both isotropic and anisotropic filters. By applying hard or soft constraints to the filter radius, the proposed approach enables the creation of a variety of structural forms, such as extruded shapes, plate-like structures, and a blend of free-form structures with the aforementioned types. Moreover, by manipulating the filter radius values across different regions within the design domain, it is possible to generate composite designs featuring a variety of structural morphologies. This adaptability allows designers to customise filter radius values in targeted regions to develop structures that meet both aesthetic preferences and functional requirements. 

In summary, this thesis establishes novel approaches to achieving diverse and competitive designs based on the parallel BESO method. The main contributions of this thesis are outlined below. First, a parallel BESO framework is proposed and implemented, equipping designers with the capability to obtain optimised solutions with unprecedented speed and resolution. Second, perturbation approaches are proposed and tested, enabling designers to use topology optimisation to create diverse and efficient designs. Third, a three-field BESO method with a variable-radius filter scheme is proposed and verified, forging a new path for creating diverse designs with multiple morphologies via topology optimisation. The research outcomes hold great potential for practical applications in architecture and engineering, where diverse and competitive solutions are in high demand.