ABSTRACT

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This paper summarises the test data obtained from an experimental investigation of reinforced concrete (RC) wide beams, which can also be described as one-way slabs, under low-rate (static) and high-rate (impact) concentrated loading applied at their mid-span. The aim of the work was to investigate key aspects of structural response such as the load–deformation behaviour, crack patterns, strength and failure modes of these basic structural elements under varying levels of loading rate. Three 125 mm thick specimens were studied and they measured 1800 mm long and 360 mm wide. They were simply supported at a span of 1600 mm. One specimen was tested under static loading, and the other two were subjected to impact loading using a drop weight. For both load rates investigated, measurements included strains, deflections and support reactions. Additional measurements for the impact test included accelerations and the use of a high-speed, high-resolution video camera to record the whole test. Digital photography was also used for the low-rate test. The use of digital photography and video recording has proved to be a valuable source of data to validate the readings of the more conventional instrumentation and also to give insight into transient features of the impact test such as crack patterns, particularly those which opened and closed during the test. The comparison between the low-rate and impact behaviour has helped further the understanding of the structural response of RC structures under varying rates of loading.

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a b s t r a c tThe present numerical investigation offers evidence concerning the validity and objectivity of the predictions of a simple, yet practical, finite element model concerning the responses of steel fibre reinforced concrete structural elements under static monotonic and cyclic loading. Emphasis is focused on realistically describing the fully brittle tensile behaviour of plain concrete and the contribution of steel fibres on the post-cracking behaviour it exhibits. The good correlation exhibited between the numerical predictions and their experimental counterparts reveals that, despite its simplicity, the subject model is capable of providing realistic predictions concerning the response of steel fibre reinforced concrete structural configurations exhibiting both ductile and brittle modes of failure without requiring recalibration.

This work examines experimentally and numerically the influence of steel fibre reinforcement on lightweight aggregate concrete (LWAC). The replacement of conventional aggregates with recycled lightweight ones has several benefits such as reducing the mass of the structure leading to more economical designs (also beneficial under earthquake loading). The experimental project showed that it was possible to produce higher strength to weight ratio of LWAC compared to normal weight aggregate concrete (NWAC) as dry densities were approximately 700 Kg/m3 lower for identical characteristic compressive strengths between 40MPa and 30MPa. This could lead to savings in materials, construction and transportation costs making it especially useful and economical for long-span and seismic-resistant structures. Conversely, LWAC is noted for its highly brittle nature due to its associated weak aggregate interlock mechanism which can be typically compensated for by increasing shear reinforcement and dowel action by means of adding higher reinforcement ratios. Nonetheless, this creates several challenges in construction such as congestion of reinforcement in critical regions as well as increased dead loads which render LWAC use counterproductive. Thus, steel fibre reinforcement emerges as a promising solution where partial or total substitution of conventional transverse reinforcement could become a possibility. This project carries out examination of the effectiveness of hooked-end steel fibre reinforcement with fibre volume fractions of Vf = 1% and Vf = 2%. The experimental investigation includes the study of direct uniaxial compression and tension (unique pullout test) and indirect splitting and flexural tensile tests. Moreover, a nonlinear finite element study has been carried out using ABAQUS to model the experiments using CDP. Currently, there is no international standards or design guidelines for steel fibre reinforced lightweight concrete (SFRLC). This project will help address that and lead to sustainable and innovative seismic design solutions in the future.

The structural behaviour of steel-fibre-reinforced concrete beams was studied using non-linear finite-element analysis and existing experimental data. The work aim was to examine the potential of using steel fibres to reduce the amount of conventional transverse steel reinforcement without compromising ductility and strength requirements set out in design codes. To achieve this, the spacing between shear links was increased while steel fibres were added as a substitute. Parametric studies were subsequently carried out and comparisons were also made with BS EN 1992-1-1 predictions. It was concluded that the addition of steel fibres enhanced the load-carrying capacity and also altered the failure mode from a brittle shear mode to a flexural ductile one. The provision of fibres also improved ductility.However, interestingly it was found that adding excessive amounts of fibres led to a less-ductile response. Overall, the study confirmed the potential for fibres to compensate for a reduction in conventional shear reinforcement.energy absorption of the control specimen M rd bending moment capacity P lateral monotonic load P BMC load calculated based on bending moment capacity P max load-carrying capacity P max,EXP load-carrying capacity based on experimental data P max,DES load-carrying capacity based on current design guidelines P max,FEA load-carrying capacity based on finite-element analysis P max,0 load-carrying capacity of the control specimen P sc load calculated based on shear capacity P u ultimate load P y load at yield P y,0 load at yield of the control specimen SI stirrup spacing increased V f volume fraction of the fibres V rd shear capacity ä y deflection at yield ä u ultimate deflection ì ductility ratio ì, 0 ductility ratio of the control specimen

The structural behaviour of steel fibre‐reinforced concrete (SFRC) has been studied using non‐linear finite element analysis (NLFEA) and ABAQUS software. An interesting feature of this work is the consideration of statically indeterminate SFRC columns. Most of the SFRC specimens studied in the literature are simply supported beams, and information on statically indeterminate columns is sparse. In addition, both axial and lateral loads were considered in order to allow for compression and flexural effects on the columns. The aim of the work was to examine the potential for using steel fibres to reduce the amount of conventional transverse steel reinforcement without compromising ductility and strength requirements. To achieve this, the spacing between shear links was increased while steel fibres were added as a substitute (spacing between shear links increased by 50 and 100 % with fibre volume fraction Vf increased to Vf = 1, 1.5, 2 and 2.5 %). The numerical model was carefully calibrated against existing experimental data to ensure the reliability of its predictions. Parametric studies were subsequently carried out, which provided insight into how the steel fibres can help reduce the number of conventional shear links.