Thesis Abstract

Abstract
Steel fibre reinforced concrete (SFRC) has gained significant attention in recent years as a promising alternative to conventional reinforced concrete due to its improved mechanical properties. In structural applications, the use of SFRC has shown potential in enhancing the shear capacity of concrete members. This study focuses on investigating the shear behavior of SFRC beams without conventional shear reinforcement. The objective is to evaluate the shear capacity of SFRC beams and compare it with conventional reinforced concrete beams. Experimental tests were conducted on a series of SFRC beams with varying steel fibre volume fractions. The beams were tested under four-point bending to assess their shear capacity. The test results were compared with control beams made of conventional reinforced concrete without steel fibres. The SFRC beams exhibited enhanced shear resistance compared to the control beams, indicating the potential of steel fibres in improving the shear capacity of concrete members. Finite element analysis was also carried out to simulate the behavior of SFRC beams under shear loading. The numerical models were validated against the experimental results to ensure their accuracy in predicting the shear capacity of SFRC beams. Parametric studies were conducted to investigate the influence of steel fibre volume fraction on the shear behavior of SFRC beams. The analysis revealed that an increase in steel fibre content led to an improvement in the shear capacity of SFRC beams. The study provides valuable insights into the shear behavior of SFRC beams without conventional shear reinforcement. The results indicate that steel fibres can effectively enhance the shear capacity of concrete beams, offering a viable alternative to conventional shear reinforcement methods. The findings of this research have implications for the design and construction of SFRC structures, where improved shear performance is desired. In conclusion, the shear capacity of SFRC beams without conventional shear reinforcement was found to be significantly enhanced due to the inclusion of steel fibres. The experimental and numerical investigations conducted in this study demonstrate the potential of SFRC as a sustainable and effective solution for improving the shear resistance of concrete members. Further research is recommended to explore the long-term behavior and durability of SFRC structures in practical applications.

Thesis Overview

While the increase in shear strength of Steel Fibre Reinforced Concrete (SFRC) is well recognized, it has yet to be found common application of this material in building structures and there is no existing national standard that treats SFRC in a systematic manner.

The aim of the diploma work is to investigate the shear strength of fibre reinforced concrete beams and the available test data and analyse the latter against the mostpromising equations available in the literature. The equations investigated are: Narayanan and Darwish’s formula, the German, the RILEM and the Italian guidelines.

Thirty articles, selected among over one hundred articles taken from literature, have been used to create the database that contains almost 600 beams tested in shear. This large number of beams has been decreased to 371 excluding all those beams and test that do not fall within the limitation stated for this thesis. Narayanan and Darwish’s formula can be utilized every time that the fibre percentage, the type of fibres, the beam dimensions, the flexural reinforcement and the concrete strength class have been defined.

On the opposite, the parameters introduced in the German, the RILEM and the Italian guidelines always require a further characterization of the concrete (with bending test) in order to describe the post‐cracking behaviour. The parameters involved in the guidelines are the residual flexural tensile strengths according to the different test set-ups.

A method for predicting the residual flexural tensile strength from the knowledge of the fibre properties, the cylindrical compressive strength of the concrete and the amount of fibres percentage is suggested. The predictions of the shear strength, obtained using the proposed method for the residual flexural tensile strength, showed to be satisfactory when compared with the experimental results.

A comparison among the aforementioned equations corroborate the validity of the empirical formulations proposed by Narayanan and Darwish nevertheless only the other equations provide a realistic assessments of the strength, toughness and ductility of structural elements subjected to shear loading.

Over the three investigated equations, which work with the post‐cracking characterization of the material, the Italian guideline proposal is the one that, due to its wide domain of validity and the results obtained for the gathered database of beams, has been selected as the most reliable equation.