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Fibre reinforced concrete (FRC) is gaining acceptance as a structural material for casting precast segments as this has proven to lead to various advantages respect to the traditional reinforced concrete, especially for improving the crack control during transient loading situations. Concentrated loads induced during the excavation stage by Tunnel Boring Machines (TBMs) is still a matter of discussion into the tunnelling construction field, this having a strong impact from both technical and economic perspectives. In this regard, although specific codes and guidelines have been published and intense research has been carried out, this pointing out the benefits of using FRC as partial or total substitution of conventional reinforcement; however, there is still not a thorough research on the effectiveness of the FRC strength class (as defined into the fib Model Code 2010) to control crack widths in tunnel linings during the TBM thrust phase. To this end, the objective of this research contribution consists in carrying out a parametric analysis, considering different FRC strength classes (including hybrid reinforcements), related with the crack patterns due to the TBM-thrust on FRC segments. This was performed by means of a comprehensive non-linear finite element (FE) numerical simulation. The results derived from this research are meant to be useful for those stakeholders involved in the design of precast tunnel linings., The first author acknowledges the Spanish Ministry of Science, Innovation and University for providing support through the PhD Industrial Fellowship (DI-17-09390) in collaboration with Smart Engineering Ltd. (UPC’s Spin-Off). This research has been possible due to the economic funds provided by the SAES project (BIA2016-78742-C2-1-R) of the Spanish Ministry of Economy, Industry and Competitiveness (MINECO)., Postprint (published version)

The increasing use of fibre reinforced concrete (FRC) as a structural material requires a constant development of new tools for design purposes. In this line, different codes and guidelines include constitutive models for FRC in their specifications. However, these constitutive models are usually based on the behaviour of steel fibre reinforced concrete (SFRC) and present several limitations on representing the full behaviour of macro-synthetic fibre reinforced concrete (MSFRC). With the aim of analysing the suitability of the constitutive models when applied on macro-synthetic fibres, an experimental program to determine the performance of MSFRC using different fibre contents and concrete mixes was performed. The study of the constitutive models was conducted through an inverse analysis using a two-dimensional analytical model to verify and compare the FRC constitutive equations of the MC2010 with the experimental results. The constitutive model of MC2010 was selected given that it is able to capture both the softening and hardening behaviour of FRC through a three-point constitutive equation. The results show that the original constitutive model of the MC2010 tends to overestimate the performance of PFRC. Moreover, it could be necessary to include an additional point on the post-cracking branch of the constitutive model to represent more accurately the full residual strength of PFRC. The results also show that the ultimate strain of the constitutive model should be extended to fully capture the performance of PFRC, especially for large deformations. This study suggests that it should be necessary to redefine the constitutive models through a new approach distinguishing between FRC blended with steel or macro-synthetic fibres., Peer Reviewed, Postprint (published version)

Over the last years, the use of fibre reinforced concrete (FRC) has increased for structural purposes. For the structural design of FRC elements, there was a need of a model that developed the behaviour of the post-cracking response of FRC. In this sense, national and international guidelines have included models to characterise the flexural behaviour of FRC (fib Model Code, EHE-08). These models gather the performance of FRC for serviceability limit state (SLS) and ultimate limit state (ULS) for either steel or macro synthetic polypropylene fibre reinforced concrete (SFRC and MSFRC, respectively). In this regard, the codes and guidelines do not distinguish between FRC comprised of steel or synthetic fibres and establish the FRC ultimate strain in 2.5%. This limitation represents the behaviour of SFRC but limits the full potential of MSFRC for large deformations. Owing to the aspects aforementioned, an extensive experimental programme has been carried out at the Universitat Politècnica de Catalunya (UPC) to characterise the behaviour of MSFRC. This research contribution is focused on an inverse analysis to derive the MSFRC constitutive equations by means of a non-linear finite element simulation. The main goal of this study is to compare the experimental results with those obtained through the simulation using the constitutive equations of the fib MC-2010. The results show a generalised underestimation of MSFRC at ultimate strain and the necessity of adjusting the constitutive equations for SFRC and MSFRC., Peer Reviewed, Postprint (published version)

The growing use of fibre reinforced concrete (FRC) on structural concrete has made that several codes and guidelines have included models for design in which the traditional reinforcement has been substituted partially or totally. Among the industrial applications, fibres as reinforcement of elevated flat slabs is gaining interest due the post-break bearing capacity of the material. This technology has already been used for real scale structures. This research contribution is focused on a parametrical analysis of FRC elevated flat slab by means of non-linear finite element simulation. The model is calibrated and compared with the real scale experimental test and with experimental slabs tested up to failure that can be found in the literature. The main goal of this paper is to carry out a parametrical analysis of the slab combining different types of reinforcement: FRC and hybrid reinforcement (fibres¿+¿conventional reinforcement) under design loads eventually choosing an amount of fibres for an actual test The results demonstrated that the combination of fibres and rebar improves the structure against failure, reduces deformation and presents a crack pattern better for cracking control., The first author acknowledges the Spanish Ministry of Science, Innovation and University for providing support through the PhD Industrial Fellowship (DI-17-09390) in collaboration with Smart Engineering Ltd. (UPC’s Spin-Off). This research has been possible due to economic funds provided by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO) through the RTC-2016-5263-5 financial support associate to the eFIB Project (building process optimization and structural element design using fibre reinforced concrete instead of conventional rebar) carried out along with SACYR Ingeniería e nfraestructura., Postprint (published version)