Recent years have seen an explosion in the number of large-scale structures such as tall buildings and long span roofs (e.g. all but one of the world's 20 tallest buildings was constructed in the last 15 years, almost all of which are over 400m in height; furthermore, it has recently been estimated that 4 million skyscrapers of 40 stories will be required by 2050 to accommodate worldwide urban population growth). However, currently the forms of such structures are usually identified in an ad-hoc manner, with very limited application of optimization techniques, despite the fact that such techniques are now routinely used in other industrial sectors (e.g. automotive and aerospace). This means that material consumption and associated greenhouse gas emissions will often be far higher than necessary, and novel structural configurations which permit inclusion of energy efficient features such as light wells or atriums will often be overlooked. In this project highly efficient mathematical optimization methods will be developed specifically for large-scale building structures, and used to automatically identify efficient layouts of structural elements. This will enable determination of the 'absolute minimum material reference design' for a given design brief, providing a powerful new means of evaluating the relative efficiency of alternative structural layouts. Methods will also be developed to automatically generate simpler and more practical structural layouts, which consume little more material than the absolute minimum quantity. The methods will be used to identify structurally efficient layouts for a range of applications, including tall building exoskeleton design and long-span canopy roof design. Considering tall buildings, a recent development has been the use of exoskeleton 'diagrids', which give a clear expression of the structural system, and are perceived to be more efficient than conventional solutions. However, the use of any predefined configuration will implicitly inhibit efficiency and vast numbers of alternative layouts will be able to be considered using the tools to be developed in this project. Considering long-span canopy roofs, such as those used in sports stadia, exhibition halls and factories, reducing material consumption by adopting a more efficient layout of elements leads to a 'virtuous circle' since as structural self-weight is reduced, so does the amount of structural material required to support this. The project will result in the development of practical tools and guidance for practitioners, and educational materials for students. Successful delivery of the research can be expected to dramatically improve the ability of engineers to design structurally efficient large-scale buildings.