| Popis: |
In last decades, the use of steel fibre reinforced concrete (SFRC) as a construction material has developed beyond the traditional applications. Despite the notable research advances in the fibre reinforcement technology and the development of guidelines and recommendations for structural design, questions continue to arise regarding the characterization and modelling of SFRC. The definition of the constitutive models of SFRC and the development of methods for the prediction of deformation and cracking of SFRC structural elements either without or with a traditional bar reinforcement have been extensively studied by many researchers, though their adequacy for certain applications still remains an issue. These subjects require further research in order to work towards an accurate and efficient design procedure. This thesis investigates the deformation and cracking behaviour of SFRC beams with and without steel bars. Special attention is paid for the analysis of residual strength of tensile SFRC – the fundamental material characteristic for analysis of SFRC structures. With the aim of identifying the residual strength responses, an extensive experimental investigation of 48 flexural SFRC elements subjected to three- and four-point loading is executed. A simple technique for prediction of residual strength from standard three-point bending test is proposed. The main advantage of the proposed technique (in comparison with the standard methods) is its capability to calculate residual strength of tensile SFRC at any given loading or deflection. For prediction of deformation and cracking behaviour of SFRC beams with bar reinforcement a numerical simulation algorithm is developed. Unlike the most of the serviceability techniques that are used specifically either for deformation or crack analysis, the algorithm based on the stress-transfer approach allows to sim-ultaneously model both the deflection and cracking response of SFRC beams with bar reinforcement. In addition to the residual strength, the laws characterising bond-slip and damage zone are the basic constitutive parameters governing the results of analysis. Being mechanically sound, the developed technique can be universally applied to any type of concrete (plain, high strength/performance) and reinforcement (steel, fibre reinforced polymer). To evaluate the adequacy of the developed technique, an experimental program consisting of 11 full scale reinforced concrete beams with varying fibre content was performed. Comparison of numerical and experimental results proved the applicability of the proposed modelling method. The author have published 14 articles on the topic of the dissertation (5 of them in the journals with an Impact Factor and 3 in the conference proceedings referred by the Clarivate Analytics Web of Science database). |
