This project investigates the use of stainless steel I-sections and shear studs in steel-concrete composite bridges. Bridge structures present many challenges to contractors and structural designers owing to harsh environments, large/variable structural loading and limited access to the sites in which they are often located. Construction and maintenance of these structures can be timely and expensive, particularly in environments where salt and water are present. Unfortunately, on some occasions in the past such as the Mianus River Bridge in Connecticut, corrosion of certain elements in bridges has led to structural collapse and loss of life. Steel-concrete composite beams, comprising a steel I-section connected to a concrete slab by shear connectors, are widely used in buildings and bridges since this system optimises the use of each material and enables beams to span long distances unsupported. However, most research to date has focussed on carbon steel in these applications. Stainless steel has been traditionally less popular owing to its higher material cost and limited available design guidance. Researchers have also increasingly turned their attention to this material in recent years, leading to a better understanding of its structural properties and performance. Stainless steel offers many advantages over carbon steel, most notably superior corrosion resistance. This reduces the need for bridge maintenance and so the higher material cost is compensated for by lower life-cycle costs. This improved corrosion resistance also reduces the likelihood of structural failure. The aim of this research project is to conduct a series of laboratory experiments (push-out tests and full member bending tests) on stainless steel-concrete composite specimens using stainless steel I-sections and shear studs in order to assess the performance of stainless steel. The experiments will be conducted in the strong floor in the structural engineering laboratory of the University of Bradford. Comparisons will be drawn between the performance of stainless steel and carbon steel components. Different types of shear stud will also be compared - welded and bolted/demountable. The demountable shear studs offer further potential advantages with regard to ease of construction/dismantling and a potentially better performance under fatigue loading than welded studs. Following the experiments, numerical models will be developed using finite element software in order to extend the results of the research and enable parametric studies. The results will eventually be used to develop guidelines for incorporation into Eurocode 4, promoting the exploitation of stainless steel to provide safer, cost-effective and lower maintenance steel-concrete composite structures.

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.

One sixth of the world's CO2 emissions from energy and industrial process are released from the production of steel and cement, most of which is used in construction. Although reducing embodied energy in structures is increasingly being considered by structural engineers, it is very difficult to achieve meaningful results with today's construction methods because the different existing mainstream structural systems, whether steel, concrete or composite construction, use similar amounts of virgin materials and have similar embodied energy values. We propose a radically different approach to reduce the environmental impact of construction: by making structural components reusable at the end of life of the structure. This can potentially reduce the use of new materials of a structure by 50%. The concept of reusable structural components has been talked about, but no feasible solution is available. Without making structural components reusable, at the end of life of a building, although all the steel and concrete materials in the building structure remain serviceable, the building is demolished destructively, larger steel elements are recycled by energy-intensive melting, and the rest of the material is landfilled. This approach to construction is clearly wasteful - of energy, emissions and potentially cost. This project aims to develop a reusable composite floor system to be used in steel/concrete composite structures. It is important that this method of construction is developed as a mainstream structural engineering solution, rather than limited to very special conditions, so as to maximize the benefits of design and construction of reusable structural components at the end of life. Steel/concrete composite structures are chosen because this building type is the most commonly used in the UK. The proposed reusable floor system is a totally different form of construction, with new modes of structural behaviour that have not been investigated before. A complete rethink of composite floor structural and fire engineering design is necessary to ensure safety of the proposed floor system. Extensive new physical tests at ambient and elevated temperatures and in fire for the different components of the proposed floor system have been planned to identify the different modes of behaviour and failure of the system. Supplemented by extensive numerical simulations, this project will develop thorough understanding of the structural and fire performance of the new structural system to develop practical design methods. This project will be carried out in collaboration between the Universities of Bradford and Manchester, which have international leading experiences in composite structural behaviour and design at ambient temperature and in fire, and have dedicated and experienced research teams and experimental facilities. A steering group, consisting of high level representatives from key construction companies, will advise the research teams to ensure practical relevance of the research and to help promote the outcomes of the research. Various impact pathways have been planned, including a dedicated website for the project and APPs for designers, promotion of the research outcome to relevant Eurocode 4 (Eurocode for composite structures) committees (where the two applicants, Professors Lam and Wang, represent the UK for structural safety (Eurocode 4 Part 1.1, or EN 1994-1-1) and fire safety (Eurocode 4 Part 1.2, or EN 1994-1-2)), and a one-day colloquium at the end of the project.

There is an urgent need for sustainable development in modern societies. As natural resources become more limited, and environmental pollution has reached alarming levels in many regions on the planet, man made activities need to switch to a more sustainable way of thinking and operation. Many governments worldwide have set ambitious sustainability targets for the near future. The UK government, specifically, has set as target the 80% reduction in carbon dioxide (CO2) emissions from all anthropogenic activities by 2050. The European Union has also included the drastic reduction of CO2 emissions, waste and energy consumption as first priorities in their agenda. The construction sector can play an important role to achieving a sustainable environment, since: a) the production of new materials is an energy intensive process, which is responsible for about 15% of the global CO2 emissions; b) buildings are usually being demolished at the end of their useful life creating waste and pollution, e.g. demolition is responsible for one third of total waste in the UK, and more than half of this waste is still sent to landfill; and c) the material demands will be doubled globally by 2050 according to recent reports. In addition, recycling is not a sustainable solution, because the recycling process is still very energy intensive and requires only marginally less energy than creating materials from scratch. A more sustainable solution is to find ways to avoid demolition of buildings at the end of their useful life. This can be done by developing innovative structural solutions that allow for the reuse of building components directly to new projects. In this way, the construction will produce less CO2 emissions (as there will be no need to manufacture new members or to recycle the old ones), much less waste will go to landfill, and the natural resources of the planet will be used more responsibly. Steel-concrete composite buildings have a large market share (more than 70% in the UK for multi-storey offices and car parks) and more than half of them use steel-concrete composite floors, i.e. the concrete slab is mechanically connected to the steel sections, which results in more economic designs. The current practice of constructing a composite floor, however, uses a connection method between the concrete slab and the steel sections that makes their separation extremely difficult; thus, the disassembly of these buildings is highly problematic. This project proposes a novel way to connect precast concrete slabs with steel sections that offers the advantages of: a) off-site fabrication of all components; b) easy and fast installation on the construction site; c) disassembly of the composite floor; and d) direct reuse of all components in new projects. The project will use experimental testing complemented by numerical analyses in order to develop the proposed novel structural system. Experiments will be conducted on both the slab-steel section connection system alone, in order to characterise its structural behaviour, and on large-scale composite beams replicating real beams in buildings. The experiments will provide evidence on the physical behaviour and the ultimate failure modes of the proposed system, whereas numerical simulations using advanced mathematical models will be used to study numerous geometrical configurations and generalise the results of the tests. Based on the results of the tests and the simulations, recommendations for the practical design of the proposed system will be proposed. The project involves collaboration with leading academics and key industrial partners in order to deliver a reliable sustainable solution for composite floor systems.

The excellent atmospheric corrosion resistance and favourable mechanical properties of stainless steel make it well suited for a range of structural applications, particularly in aggressive environments or where durability and low maintenance costs are crucial design criteria. The main disadvantage hindering the more widespread usage of stainless steel in construction is its high material cost and price volatility. However, life-cycle costing and sustainability considerations make stainless steels more attractive when cost is considered over the full life of the project, due to the high potential to recycle or reuse the material at the end of life of the project. The design of stainless steel structures is covered by a number of international design codes, which have either recently been introduced or or were recently amended in light of recent experimental tests, thus indicating the worldwide interest stainless steel has received in recent years. Despite the absence of a well-defined yield stress, all current design standards for stainless steel adopt an equivalent yield stress and assume bilinear (elastic, perfectly-plastic) behaviour for stainless steel as for carbon steel in an attempt to maintain consistency with traditional carbon steel design guidance.Given the high material cost of stainless steel, improving the efficiency of existing design guidance is warranted. Improvements can be made either by calibrating the existing design procedures, some of which are based on engineering judgment and limited test data, against additional experimental results, or by devising more accurate design approaches in line with actual material response. In any case more efficient yet safe design rules are desirable. The majority of published research articles on stainless steel structures focus on the response of individual members. Due to insufficient relevant experimental data, no rules are given for plastic global analysis of indeterminate stainless steel structures in any current structural design code, even though the ductility of stainless steel is superior to that of ordinary structural steel. The controversy of not allowing plastic design for an indeterminate structure made of a ductile material is obvious in Eurocode 3:Part 1.4 where it is explicitly stated that "No rules are given for plastic global analysis" even though a slenderness limit for stocky elements is specified in the same code. Moreover, because of the lack of relevant experimental data for stainless steel frames, no specific design provisions to account for second order effects in stainless steel frames are specified in any stainless steel design code. Deficiencies in current design guidance puts stainless steel at a disadvantage compared to other materials thereby hindering its use in applications where it might be the preferred solution, had the design standards not imposed strict restrictions to its design due to a gap in current knowledge. The proposed project aims at investigating the structural response of stainless steel indeterminate structures and developing appropriate design rules, by means of experimental studies on two-span continuous beams, as well as portal frames and advanced numerical analyses. Experimental results, suitable for the validation of numerical models, will be generated and will allow a rigorous study of the ultimate response of indeterminate stainless steel structures. The accuracy of current design procedures (i.e. not allowing for plastic design or partial moment redistribution in indeterminate structures) will be assessed and the possibility to apply plastic design to stainless steel structures will be explored. It is envisaged that the proposed project will lead to design rules suitable for incorporation in EN 1993: Part 1.4.