Behaviour of High- and Ultra-High Performance Fibre Reinforced Concrete Flexural Members

Abstract

Concrete is a quasi-brittle material that increases in brittleness as the compressive strength increases and as such plain high-strength concrete always fails in an explosive manner. Incorporation of randomly distributed discrete non-metallic or metallic fibres into conventional concrete mixes has now been well-recognized as a feasible solution to address the issue of the low material ductility of concrete. The presence of fibres in concrete can prevent wider cracks on the concrete structural elements under instantaneous and sustained loads and an associated refinement of the pore structure and mitigations of micro-cracks also effectively contributes to enhancing the durability-related material properties. This thesis presents a series of research work investigating the behaviour of various types of high- and ultra-high performance concrete flexural members. The work starts with an investigation to develop mix proportions for ultra-performance concrete with and without fibres to achieve the desired dimensional stability as reported in Chapters 2 and 3 in this thesis. The optimal concrete recipe is then used continuously through the entire experimental program to manufacture the flexural members for investigations, as presented in Chapters 5 to 8, where the behaviour of a series of high- and ultra-high performance concrete flexural members, including fibre-reinforced concrete (FRC) simply-supported beams, ultra-high performance fibre reinforced concrete (UHPFRC) continuous beams, curved beams, skew slabs and also sandwich panels using ultra-high performance concrete (UHPC) face sheets, are experimentally studied. Having experimentally investigated the performances of these high- and ultra-high performance concrete flexural members, in Chapter 4, a generic analysis technique, (the segmental based moment-rotation approach), is extended to simulate the behaviour of highand ultra-high fibre reinforced concrete flexural members. This approach is based on the fundamental Euler-Bernoulli postulation that plane remains plane and applies the wellestablished mechanics of partial interaction (PI) theory to simulate crack formation and crack widening including the influence of the discrete fibre reinforcement. Moreover, in Chapters 6 to 8, analytical approaches, in terms of the fundamental mechanics based closed-form models are also derived using energy theorem to predict the performance of non-orthogonal ultra-high performance fibre-reinforced concrete flexural members.