Structural Behaviour of Steel Fibre Concrete Floors

Abstract

Concrete as a heterogeneous material is a suitable choice for resisting high compressive stresses, whereas it exhibits a low resistance toward tensile stresses as well as a very brittle behaviour. Various alternatives have been introduced to enhance the tensile behaviour of concrete, such as conventional reinforced concrete and steel fibre reinforced concrete (SFRC). Steel fibre reinforced concrete benefits the construction process by reducing the labour effort that decreases the construction time and thus may be beneficial for the construction economical cost. Furthermore, several kinds of research have shown that SFRC enhances toughness and other properties of concrete, a fact that makes SFRC an attractive choice from a structural behaviour point of view. One of the promising applications of SFRC is for pile-supported slabs. Nevertheless, the use of SFRC is still limited, since various challenges shall be considered, such as cracking, which can be due to shrinkage, load and temperature.

Although there are several available codes for design of conventional and steel fibre reinforced concrete, and they are accurate for many structural elements, these codes are still incapable of determining the actual structural behaviour when the structural element has specific boundary conditions such as continuous slabs, since a significant discrepancy has been recognized between experimental results and proposed design methods. For instance, in continuous slabs, the difference could stem from factors such as arching action phenomenon. This phenomenon is dependent on the boundary conditions of the structure, whereas it is independent of the used material. In other words, the arching action phenomenon can arise from the presence of special boundary conditions, regardless of what the used material is. The effect of arching action is favourable, but meanwhile, including this effect in the design procedure could make it intricate. Therefore, this master’s thesis has been directed toward investigating the structural behaviour of SFRC and how the boundary conditions could impact this behaviour. To carry out this investigation, a set of numerical analyses has been implemented. The first numerical analysis was for notched three-point bending beam, which has been used as a tool to verify the tensile response of SFRC. The second one is a numerical analysis of round indeterminate panel test, which is by the purpose of evaluating the influence of frictional contact zone on the structural behaviour of the round panel, where the frictional contact zone is between the round panel and its continuous support. The last one was a numerical analysis of a full-scale pile supported slab to investigate the impact of arching action phenomenon on its structural behaviour.

As expected, the use of SFRC increases the ductility of concrete and could result in hardening deflection. Additionally, the numerical analysis of the notched beam indicates that adaptive inverse analysis (AIA) is a good representative for the tensile response of SFRC. Moreover, the results of round indeterminate panel test exhibit that the friction forces between the round panel and its continuous support increase the post-cracking capacity and therefore, these forces will cause an overestimation in the evaluation of post-cracking capacity. Finally, the numerical analysis of pile supports slab displays that arching action phenomenon increases the capacity of an interior panel while it is subjected to uniformly distributed load or point load. The effect of arching action is favourable and could be utilized to perform a more economic design.