Characterization tests for predicting the mechanical performance of SFRC floors: identification of fibre distribution and orientation effects (original) (raw)
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Structural Behaviour of Steel Fibre Concrete Floors
2019
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
The post-cracking energy absorption capacity is the concrete property most benefited by steel fibre reinforcement, usually designated by toughness. Different test set-ups, test procedures and parameters have been proposed to evaluate the toughness of the steel fibre reinforced concrete (SFRC), but none of them has received a general acceptation by scientific and technical communities. As a consequence, designers put some reserves on the use of SFRC, because they are not confident on the design practice to be adopted, resulting in the exclusion of SFRC in applications where it could be the most suitable solution. In the last years RILEM TC 162 -TDF has published documents where recommendations for characterizing and designing SFRC structures are proposed. A general acceptation of these recommendations can be only taken if they are deeply analysed and checked by a large number of research centres. This work intends to give some contribution for this analysis. It has also the purpose of evaluating the influence of the fibre content, percentage of cement replaced by fly ash and SFRC age on the post-cracking behaviour of the SFRC, under the experimental framework recommended by RILEM TC 162 -TDF.
2020
Steel fibre-reinforced concrete (SFRC) is widely applied in the construction of civil infrastructure projects, including the following: industrial floors, slabs, walls, and foundations. The application of steel fibres in the reinforcement of concrete remarkably improves the postcracking behaviour of such concrete. In order to estimate this property, the energy involved in absorption is measured by using several valid testing standards: EVS-EN 14651:2005, EVS-EN 14488-5:2006, and ASTM C1550-12a. The objective of this study was to carry out a comparable analysis of the results that have been obtained using previously-mentioned standards and to be able to find a more reliable method for the determination of the fracture toughness of SFRC specimens. Experiments were carried out in accordance with the chosen standards. It was concluded that procedure involved in the ASTM standard provides a smaller variability of results with better levels of repeatability, therefore a smaller volume of ...
Fiber reinforced concrete: from flexural tests to solid slabs
Proceedings of the 10th International Conference on Fracture Mechanics of Concrete and Concrete Structures, 2019
Tensile behavior of fibre reinforced concrete is assessed based on flexural tests where specifically the post cracking strength values are of interest. However, the residual tensile strength values obtained based on such characterization test exhibit a very high scatter which is mainly due to the variation of number and orientation of fibres at the fracture plane. This rather unrepeatable behavior may cast doubt on the overall performance of a structure reinforced only with fibres and may question the validity of estimated tensile strength parameters that are used in the design of such from one specimen to another structures. While there is evidence that fibre reinforced concrete structures show a behavior that can be predicted by the average material properties, no strong proof is yet available. If so, then the low characteristic value of residual strength values may be a very conservative starting point for design of such structures To validate the reliability of design approach proposed for fibre reinforced concrete structures, twelve nominally identical fibre reinforced concrete slabs sized 2000×2000×150 mm, and twelve notched specimens sized 150×150×600 mm are tested, and the results are compared. Further, a yield line method is employed to predict the ultimate load bearing capacity of the slabs based on the tensile parameters obtained from the characterization tests. The results show that the average material properties can satisfactorily predict the bearing capacity of the slabs. FraMCoS X Conference.
Assessment of the fibre orientation factor in SFRC slabs
2014
The design of steel fibre reinforced concrete (SFRC) structures is evolving towards a new approach that uses correction factors to consider differences between the small-scale characterization specimens and the realscale elements. Recently, the Model Code 2010 proposed an orientation factor (K) that accounts for the effects of the orientation in the structural response of elements. The present study focuses on the identification of this factor in SFRC slabs with different dimensions. For that, flexural tests on real-scale slabs were conducted and the fibre orientation was assessed with an inductive method. A finite element analysis showed the differences between the experimental curves and the prediction of the Model Code without considering K. Based on the results obtained, a range of values is proposed for K and validated. This study sheds light on possible modifications that this philosophy of design might require to better reproduce the behaviour of slabs.
2019
Most concrete biaxial behaviour investigations are focused on biaxial compression due to the complexity of biaxial test set up. This paper is aimed to construct a simple and economic biaxial testing frame for conducting a biaxial tensile test on plain concrete and steel fibre reinforced concrete (SFRC). It is also aimed to compare the biaxial tensile behaviour of the current study with the previous research by using different testing techniques under an equal stress ratio. Lever arm principle is applied in the proposed biaxial test set up. For SFRC, hooked-end type steel fibre with fibre volumetric fractions 0%, 0.5%, 1.0% and 1.5% are used. Uniaxial tensile strength of plain concrete is greater than biaxial tensile strength in SFRC. For plain concrete, the opposite result is obtained. The biaxial tensile strength is insignificantly affected by the increment of fibre volumetric fraction but the post-cracking behaviour of concrete is enhanced with the inclusion of steel fibre, which ...
The mechanical behaviour of steel fibre reinforced concrete
Materials Today: Proceedings, 2023
Concrete ground slabs are essential components of modern buildings and structures. This common structural element has been used in great numbers in buildings and structures of various forms and sizes throughout the world for decades. The utilisation of fibre reinforced concrete for ground slab purposes has gained significant momentum in recent years. The third edition of report TR34, published by the UK Concrete Society in 2003, has paid attention to the design of concrete ground slabs with significant emphasis on the use of steel and synthetic fibres as an alternative to fabric reinforcement. TR34 is currently under review and this paper attempts to contribute towards a better understanding of the mechanical behaviour of steel fibre reinforced concrete slabs under step loading conditions. This work reports on tests carried out at different locations (centre, edges and corners) of a 6. 0 3 6. 0 3 0. 15 m steel fibre reinforced concrete slab. A significant difference was found between the test results and theoretical values derived using available design codes. Magazine of Concrete Research Volume 64 Issue 7 Mechanical behaviour of a steel fibre reinforced concrete ground slab Alani, Beckett and Khosrowshahi Magazine of Concrete Research Volume 64 Issue 7 Mechanical behaviour of a steel fibre reinforced concrete ground slab Alani, Beckett and Khosrowshahi Magazine of Concrete Research Volume 64 Issue 7 Mechanical behaviour of a steel fibre reinforced concrete ground slab Alani, Beckett and Khosrowshahi Magazine of Concrete Research Volume 64 Issue 7 Mechanical behaviour of a steel fibre reinforced concrete ground slab Alani, Beckett and Khosrowshahi Magazine of Concrete Research Volume 64 Issue 7 Mechanical behaviour of a steel fibre reinforced concrete ground slab Alani, Beckett and Khosrowshahi
Constitutive model for fibre reinforced concrete based on the Barcelona test
Cement and Concrete Composites, 2014
Several constitutive models for fibre reinforced concrete (FRC) have been reported in the past years based on the flexural performance obtained in a bending test. The Barcelona test was presented as an alternative to characterize the tensile properties of FRC; however, no constitutive model was derived from it. In this article, a formulation to predict the tensile behaviour of FRC is developed based on the results of the Barcelona test. The constitutive model proposed is validated by simulating the results of an experimental program involving different types of fibres and fibre contents by means of finite element software. Moreover, the simplified formulation proposed is compared with constitutive models from European codes and guidelines.
More efficient and industrialised construction methods are both necessary for the competitiveness of in-situ concrete and essential if the construction industry is to move forward. At present, the expenditure on labour (preparation and dismantling of formwork, reinforcing, and casting and finishing of concrete) almost equals the cost of material. Fibre-reinforced concrete (FRC) extends the versatility of concrete as a construction material, offers a potential to simplify the construction process and, when combined with self-compacting concrete, signifies an important step towards industrial construction. However, a barrier to more widespread use of FRC has been the lack of general design guidelines which take into account the material properties characteristic of FRC, i.e. the stress-crack opening (sigma-w) relationship. The presented work has been focused on FRC, showing a strain-softening response, and the interrelationship between material properties and structural behaviour. Thi...