Rationalization of Layout Optimization Result by Updating Discretization of the Design Domain

Truss layout optimization provides a means of identifying the global optimal arrangement of truss bars capable of transmitting a given load or loads to defined support points within a defined design domain. However, the solutions obtained are generally complex and lead to structures with far too many members to be practical, especially when fine discretization of the design domain is employed. In this paper, a heuristic approach to the practical rationalization of optimal layouts is proposed, based on the observation that fan-like segments of bicycle-wheel structures often appear in multiple places in an optimal layout, with a central 'hub' joint of high valence linking through 'spokes' to a curved 'rim'. In this proposed method, the global optimum layout of a given problem is first obtained, and joints that are not used in the optimal truss are removed from the design domain. Subsequently, 'hub' joints of high valence are identified, as are the 'rim' joints they are connected to. A new discretization of the design domain is then produced, which reduces the density of joints in the curved 'rim'. A second layout optimization is then conducted to generate a more rational and buildable truss, with only a small increase in structural weight compared to the global optimal. Using two case-studies, the effectiveness and the efficiency of the proposed approach is validated.