Two-scale numerical simulations for fibre reinforced cementitious composites

Adding fibres to concrete improves its resistance to cracking. This is important because cracking in all types of plain, reinforced and prestressed concrete structures can lead to significant durability problems, such as the corrosion of steel reinforcement. Using fibre reinforced concrete in place of normal concrete improves durability by limiting the widths of any cracks that occur. In some situations, fibre reinforced cementitious materials (FRCCs) are used without conventional reinforcement; examples being, factory floors, tunnel linings and structural overlays. In every application of a fibre reinforced cementitious material, the control of cracking is a critical design issue. This means that a designer needs to be able to predict the extent and nature of cracking at all stages of a given loading history and to make sure that the material, including the type of fibre used and fibre content, satisfies cracking and ductility design criteria. When FRCCs are used in structurally complex situations, simplified analysis procedures are not applicable. In these circumstances, designers use computer models, usually based on finite element methods, to simulate the behaviour of the structure or structural component. Current finite element material models for FRCCs do not provide detailed information on cracking at different scales. This means that designers do not have the computational tools they need to reliably design FRCC structures. The inadequacy of current models provides the motivation for the work of this proposal, the aim of which is to develop a new two-scale approach for simulating the behaviour of FRCC materials that is applicable to the analysis of full-scale structures. In developing the model, careful consideration will be given to the way that cracks first develop at a small (micro) scale and then to how these small cracks combine to form large (macro) cracks. The final model will be implemented in a development version of an engineering software package. The ultimate aim of the work is that the new model will be incorporated into a commercial piece of software that is available to designers. This should, directly and indirectly, bring benefits to everyone involved in the analysis, design and construction of structures formed from fibre reinforced cementitious materials.

Fibre reinforced cementitious materials (FRCCs) are more durable than standard cement-bound materials (e.g. concrete). The enhanced mechanical properties of FRCCs also leads to thinner structural sections and a reduction in material usage. Both of these factors imply that the more FRCCs are used to replace standard concrete, the lower will be the environmental impact of the cement and concrete industry.
The link between a new accurate computer model for FRCC materials and the environmental impact of the construction industrial may appear tenuous but it is only when FRCCs are used efficiently and safely that the environmental benefits can truly be gained. The author contends that the existence of a widely available reliable computational tool for analysing FRCC structures will lead to more of this material being used in practice and to FRCC structures being more durable, and consequentially to the above environmental benefits.
In addition to the aforementioned benefits, the project research has many other potential beneficiaries, including;
1. Engineering software companies in general and the company LUSAS in particular with whom the applicant has strong and well-established links;
2. Engineers who design structures and structural components formed from FRCC materials, who will gain a new accurate tool for analysing the behaviour of these structures;
3. Private clients, national and local governmental bodies, whose structures will be better designed and as a result less prone to cracking;
4. Research and development organisations (e.g. CIRIA, BRE) who have a strong interest in FRCC materials being used efficiently and safely;
5. Professional engineering institutions (e.g. ICE, IStructE) and information bodies (e.g. Concrete Society) by raising the profile of UK research on civil engineering materials;