Engineers often expend considerable effort identifying the most efficient cross-section sizes for the individual structural members forming a structure, but may neglect to check whether members are optimally positioned, or are even needed at all. This can lead to far more material being used to form a building structure than is needed. To address this, layout optimization can potentially be used early in the design process to identify efficient arrangements of structural members. This paper introduces an interactive design approach that combines parametric modelling and layout optimization, using an adaptive ‘member adding’ technique to allow large scale problems to be solved on a standard desktop PC. Incorporation of the approach in Rhino-Grasshopper allows integration of geometric modelling and structural layout optimization within a single interactive modeling environment. This paper briefly outlines the underlying theory and implementation details, and then describes application of the approach to benchmark problems and a case study problem, a three-centred space frame arch roof. In this case it is shown that a 30% reduction in material usage can potentially be achieved through the use of a layout optimization-based approach, but that measures to improve the practicality of the solutions for use in practice are required. This is being addressed as part of a new collaborative research project involving the Universities of Bath, Sheffield and Edinburgh
