Performance-Based Optimisation of Novel Lightweight Steel Frame Systems for Rapid, Economical and Sustainable Construction

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.

WHO WILL BENEFIT AND HOW?
The cold-formed steel (CFS) global market is growing very rapidly in China and North America (see section 2.6 for more information). This proposal will be an important step in tackling the gap in knowledge and tools for optimisation of CFS systems and will develop a new generation of high-performance dual wall-frame CFS systems. The main beneficiaries from the project will be:

- CFS industry: The project will provide the UK CFS industry with a framework to develop technology to increase and diversify their markets in the UK and abroad. The high-performance dual wall-frame systems will help CFS industries by enabling faster uptake of CFS structures.

- End users: Consultants, contractors, engineers, practitioners and governmental agencies will benefit from advanced optimisation tools, basic design recommendations and design examples. The performance-based optimisation framework can be directly used to optimise existing CFS structural systems and modular systems, and hence contribute to the competitiveness of UK consultants and contractors by providing more efficient design solutions.

- Academics: See section on Academic Beneficiaries.

- Professional bodies: SCI, IStructE, ICE, AISC, and NHBC will benefit from the novel performance-based optimisation approach for more efficient design of CFS structures, and high quality results derived from experimental tests and advanced FEA simulations.

- Society: The proposed project will improve the quality of life by developing more resilient and robust structures to cope with climate change as well as man-made and natural hazards.

- People: The research programme will train a highly skilled post-doctoral research assistant (PDRA) by providing him/her with the opportunity to work in partnership with a PhD student, the PI and an experienced technician at the University of Sheffield. The PDRA will attend an international conference and various UK workshops and seminars, and will be actively involved in engagement activities with industrial consultants and national and international research teams. Such training will have a direct economic impact via the provision of skilled workers who may subsequently be employed by any beneficiary organisation.

- Environment: The proposed project will help environment by reducing CO2 emissions and embodied energy, through decreasing structural weight and better use of material. It is estimated that if just 5% of the annual need of 4 billion m2 for new constructions worldwide were built from the new CFS system, it could save around 4 million tonnes of steel. This would result in about 3.5 million tonne reduction of CO2 emissions and 70,000 TJ embodied energy per year (see 'Pathways to Impact').

WHAT WILL BE DONE TO ENSURE THAT THEY HAVE THE OPPORTUNITY TO BENEFIT?
- Basic design recommendations and design examples will be prepared for use by engineers and practitioners (developed in close collaboration with members of the industrial steering committee).

- Improved optimisation design tools will be made available, for incorporation in software usable by engineers.

- Representatives of key Uk's CFS industry will participate on the project steering committee to ensure the impact of the work is maximized.

- Presentations will be made at professional meetings and key papers will be submitted to professional as well as academic journals.

- A workshop will be organised at Sheffield assembling related cross disciplinary researchers, project supporters and potential beneficiaries to ensure the take-up of the new technology and benefit international researchers and UK organizations.

WHEN?
The academic and professional benefits of the research will start arising just before the end of the project, and as soon as the first experimental data are processed and published. Major benefits to CFS industry should start to be realised within 1 to 2 years of completion of the research.