VILNIUS TECH Library invites you to follow the published new dissertations. The dissertation „Moment–curvature analysis of concrete beams reinforced with steel bars and fibres“ prepared at VILNIUS TECH by Amarjeet Kumar. The dissertation was prepared in 2021–2026. Scientific consultant – Prof. Dr Habil. Gintaris Kaklauskas.
The dissertation was defended at the public meeting of the Dissertation Defence Council of the Scientific Field of Civil Engineering in the Aula Doctoralis Meeting Hall of Vilnius Gediminas Technical University at 2 p.m. on 16 September 2026.
This dissertation presents a simplified curvature-based analytical framework for predicting the cracking behaviour of reinforced and steel fibre-reinforced concrete (R/SFRC) beams subjected to flexural loading. Existing analytical and code-based approaches rely on experimentally determined residual tensile-strength parameters and simplified constitutive assumptions, resulting in inconsistent deformation predictions. Therefore, this research develops an analytical model to predict the moment–curvature response of R/SFRC members without direct dependence on residual tensile strength testing. The First Chapter examines the mechanisms governing deformation and cracking in R/SFRC beams with and without steel bars subjected to bending. Various analytical approaches for evaluating serviceability performance are reviewed, with particular emphasis on curvature-based analysis as a fundamental parameter for describing structural response. Existing curvature models and the theoretical backgrounds are critically discussed, followed by a survey of previously proposed curvature formulations for deformation and cracking assessment. The Second Chapter presents the development of an enhanced analytical moment–curvature model for R/SFRC members by extending the formulation proposed by Kaklauskas et al. (2024). The proposed model incorporates fibre contribution at both cracking and fully cracked stages through two parameters, γ₁ and γ₂. In addition, the ACI-based cracking moment formulation was replaced with a Eurocode 2 approach to improve compatibility with European design standards. Regression-based expressions for these parameters were established using an extensive experimental database and validated against existing analytical models and code-based formulations, including Model Code 2020 and RILEM 162 TDF. The proposed model demonstrated improved predictive accuracy, achieving an overall prediction error of approximately 1.5% with a coefficient of variation of 0.228. The Third Chapter presents an experimental and analytical investigation of R/SFRC beams reinforced with conventional and dual hooked-end steel fibres. The proposed framework successfully described the tension stiffening behaviour of the tested members. Beams reinforced with dual hooked-end fibres exhibited significantly higher γ₂ values, indicating enhanced post-cracking behaviour, extended tension-stiffening response, and improved serviceability performance. Comparisons with standard code-based formulations showed that Model Code 2020 generally provided more accurate moment–curvature predictions than RILEM 162 TDF, while code-based approaches tended to overestimate stiffness, particularly for beams with lower reinforcement ratios.
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