Topology optimisation for more efficient design
The past few years have witnessed a growing interest by the architectural community in topology optimisation as a means of generating aesthetic and efficient structural forms using computational means. By linking architects and structural engineers in the conceptual design stage, topology optimisation opens an array of opportunities for achieving more efficient design. On the one hand, the architect’s input is inspired by optimal structural forms that often resemble structures found in nature. On the other hand, the engineer is able to restrict the design so that it makes optimal use of resources and is physically viable. Considering recent technological advancements, one can envision a strictly digital design process, beginning with finding the optimal structural form using computational methods and ending in robotic manufacturing. However, making this vision a reality requires further development of topology optimisation procedures to account for realistic mechanical models – including inelastic material response and such high-order effects as buckling. Achieving this was the mission of the EU-funded TOP-CIVIL project. ‘In order for this computational tool to be attractive for practicing architects, it needs to be able to deliver accurate results in short time, preferably with an interactive interface – an application for architects to “play” with,’ says TOP-CIVIL Project Coordinator Oded Amir. ‘Thus, the main challenge we faced was in achieving interactive abilities while considering rather complex mechanical models.’ A four-step process TOP-CIVIL researchers set out to develop topology optimisation as a digital design tool for structural engineers and architects. The research consisted of four so-called building blocks, with the first two parts focusing on increasing the efficiency of 3D topology optimisation procedures that can be implemented in CAD software and executed on a standard PC. ‘First, we integrated multigrid preconditioning into a PCG iterative solver, or MGCG, for solving the state equations in 3D topology optimisation problems,’ explains Amir. In a second phase, researchers further reduced computational time by switching from a minimum compliance formulation to a minimum volume formulation and by exploiting the benefits of stiff preconditioning in a reanalysis-based procedure. ‘Together, these first two phases led to the development of 3D topology optimisation procedures capable of solving problems with hundreds of thousands of finite elements within minutes and using a single processor,’ says Amir. ‘This paved the way for efficient implementations in plug-ins for CAD software, which is the overall target of the project.’ The last two segments of the project focused on incorporating realistic mechanical models. ‘In the third part of the project, an effective approach was formulated for topology optimisation of skeletal structures (trusses and frames) that accounts for all buckling considerations,’ explains Amir. ‘Whereas in the fourth part of the project we focused on the optimisation of reinforced and prestressed concrete.’ A suite of computational procedures According to Amir, the results achieved by the TOP-CIVL project provide architects and engineers with a valuable suite of computational procedures. ‘By adopting the developed optimisation-based approaches, practitioners can achieve a reduction in material consumption in the construction industry and enhance architect-engineer collaboration in early design stages,’ he concludes.
Keywords
TOP-CIVIL, CAD, architecture, structural engineering
