Structural effects of temperature variations on macro-synthetic fibre reinforced concrete segmental linings
- Autores: Amir Hossein Farmanara Bozorgzad
- Directores de la Tesis: Albert de la Fuente Antequera (dir. tes.), Pablo Pujadas Alvarez (codir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2020
- Idioma: español
- Materias:
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- Resumen
The use of fibre reinforced concrete (FRC) as a construction material has been expanded beyond the traditional applications since the publication of design codes and guidelines. Due to its efficient and economical applications in comparison to conventional rebars, the industry is demanding FRC with increasing structural responsibilities and, in some cases, with the fibres as the only reinforcement.
One of the main applications of FRC is in the construction of precast tunnel linings used by tunnel boring machines (TBM). The functionality of tunnels is highly dependent on tunnel linings and their structural performance, while in terms of structural design, several requirements determine which type of reinforcement is best suited for the precast tunnel linings. These requirements consider different loading actions that take place in transient situations, construction phases and service life; however, due to the circular cross-section, tunnel linings are generally under compressive loads during the service life. Thus, the likelihood of the cracking of the linings increases during the transient and construction phases in which a minimum reinforcement is required. Macro steel fibre and macro synthetic fibre are feasible reinforcements for this purpose. However, synthetic fibres are sensitive to temperature as the designed capacity of the linings might be different due to temperature variations.
Despite the remarkable advances in the fibre reinforcement technology, questions continue to arise regarding the effectiveness of the synthetic fibres at different temperatures. Therefore, pre- and post-cracking characterizations of the mechanical properties of synthetic fibre reinforced concrete (SynFRC) at very low and high temperatures, and comparison of the residual behaviour of real scale samples reinforced with synthetic fibre/steel fibres at room temperature and elevated temperatures are going to be researched in this thesis. Furthermore, FE modelling will be carried out to simulate the behaviour of the real scale samples at room and elevated temperatures. These subjects require further research in order to work towards an accurate and efficient design procedure.
In this framework, the first subject presents an experimental program for characterization of the mechanical properties of SynFRC notched samples. Technical requirements demanded by the fib MC (2010) when synthetic fibres are the only reinforcement for the concrete elements were considered. Following this experimental program, samples were subjected to very low and intermediate elevated temperatures. In order to evaluate the behaviour of the matrix, residual strengths of the samples at different CMODs were compared with those at 20º C.
The second subject compares the behaviour of the real scale linings while subjected to elevated temperatures. One real scale sample reinforced with synthetic fibres/steel fibres was exposed to a Hydrocarbon fire scenario and the bending behaviour of the lining was compared with a non-exposed sample. The results of this test indicate that the exposed samples noticeably lost bearing capacity both in terms of pre- and post-cracking strengths.
The last subject focuses on the numerical simulations of the flexural behaviour of FRC. For that, a non-linear FE model to simulate the flexural behaviour of FRC subjected to bending forces was developed. The results of the numerical model indicated that fib MC (2010) is not temperature sensitive; thus, a new constitutive model to simulate the pre- and post-cracking responses of the notched SynFRC was creacreated. The new constitutive model allowed confirmation that the pre- and post-cracking responses of the samples decrease at higher temperatures. Subsequently, a non-linear FE model to simulate the flexural behaviour of the real-scale linings (exposed and non-exposed samples) was performed. With reference to the results, the FE model successfully simulated the bending behaviour of the samples.
