The legally binding UK government target to reach net zero carbon emissions by 2050 cannot be achieved without minimizing the carbon footprint of the construction sector. Over one-quarter of the world`s annual steel production is used in the construction of buildings but a study based on steel-framed designs for schools, offices and residential buildings, sourced from leading UK design consultancies, reveals the average material utilisation ratio for typical steel buildings is below 50% of their capacity. This suggests steel content in buildings could be significantly reduced by designing for minimum material, which would annually avert 214 million tonnes of carbon dioxide emissions worldwide. To reduce steel consumption in construction, the development of novel, materially efficient and sustainable lightweight structures is essential. There's a global need for housing as populations grow which creates tension with our need to cause less emissions by building less or more efficiently. Light steel frame (LSF) structures made of cold-formed steel (CFS) stud-walls and joisted floors are gaining growing popularity in modern construction practice worldwide, both in new developments and as a cost-effective and low-carbon solution for vertical extensions to existing buildings. The ease of offsite manufacturing utilising LSF structures offers many benefits compared to traditional methods, including: (a) improved quality and productivity, reduced material use, less wastage and savings of 30-50% in total construction time and associated costs; (b) flexibility for more tailored design solutions complying with the Design for Manufacture and Assembly approach; and (c) scalability for the technologies around automated construction. LSF systems can, therefore, directly contribute towards meeting the UK Government's ambitious house building commitments and reducing the initial cost of construction and whole life cost of assets, and CO2 emissions by 33% and 50%, respectively. However, the current use of LSF structural systems is limited due to critical drawbacks such as low local buckling resistance of thin-walled CFS elements, low lateral stiffness and robustness of typical LSF systems and limitations of current design and optimisation approaches to exploit their full capacity. These challenges should be addressed before LSF systems can be widely used both in the UK and overseas.

Cold-formed steel (CFS) structures offer an economic and sustainable alternative to traditional construction techniques, and are increasingly adopted in modern building construction due to their light weight, speed of construction and recyclability. However, typical CFS wall-panel structures have the following limitations that should be addressed before they can be widely used in modern building construction: 1) Low buckling resistance and ductility in CFS members and joints; 2) No generic method for optimisation of CFS structural systems, capable of taking into account both manufacturing and construction constraints; 3) Extensive reliance on fixed load-bearing walls. The main aim of the research is to develop a novel performance-based optimisation framework to address the challenging optimisation problems associated with complex CFS structural systems at both element and structural levels. The framework will be used to develop a new generation of high-performance dual wall-frame CFS systems, which are suitable for tall buildings and resilient to extreme load conditions. The overall objectives of the project are to: 1- Enhance strength and ductility of CFS structural systems to increase collapse resistance and overall safety under extreme events (such as blast and strong earthquakes), through the development of special connections and high-performance dual wall-frame systems. 2- Decrease structural weight and construction cost through advanced CFS section optimisation, accounting for dimensional and manufacturing limitations, and by developing a novel performance-based optimisation framework to obtain cost-effective CFS structures with better structural performance at serviceability and ultimate limit states. 3- Increase structural and architectural design flexibility by developing optimised CFS frame systems that eliminate (or reduce) the need for fixed CFS load-bearing wall panels. The output of the proposed research will give a competitive advantage to the UK construction sector and will have a long term impact on UK economic growth by developing more efficient light-weight steel structural systems that can reduce overall construction costs and provide higher strength and ductility. The work will be conducted in partnership with key UK CFS industries. Industrial liaison and dissemination activities, including a project conference, are planned to ensure the take-up of the new technology and benefit international researchers and UK organisations.