Design of FRC tunnel segments considering the ductility requirements of the Model Code 2010

Abstract

Fibre reinforced concrete (FRC) is used to improve the mechanical response of precast segments for tunnels. The structural use of the material has been regulated by national codes and, recently, by the Model Code 2010 (MC 2010, hereinafter). In this regard, it is necessary to update the philosophy applied to the design of tunnel segments in compliance with the most recent guidelines, evaluating their applicability and repercussion. The objective of this paper is to present a critical analysis of the design of FRC segments according to the ductility requirements from the MC 2010; an alternative approach is proposed that is compatible with the condition found in some tunnels. The repercussions of both approaches are evaluated for the Metro Line 9 from Barcelona using results obtained in an experimental program with full-scale segments. The study suggests that the alternative approach may be applied under certain conditions, leading to a reduction in the fibre consumption. Keywords: Barcelona Metro Line, Cracking bending moment, design, ductility, FRC, precast segments.Tunnelling and Underground Space Technology 2 INTRODUCTIONFibre reinforced concrete (FRC) is a composite material used to improve the mechanical response of precast segments for tunnels [1][2][3][4], enhancing their ductility and fire resistance as well as their mechanical performance during transient load stages. Due to these advantages, the use of structural fibres contributes to the replacement of traditional passive reinforcement, accelerating the production process and increasing the competitiveness of the FRC. Proof of this are the numerous experiences in which precast FRC segments have been used in highway (RT), railway (RWT), metro (MT), water supply (WTT), gas transport (GPT) and service (ST) tunnels. Table 1 [4][5][6] summarizes some of the main applications already in service or under construction.The structural use of fibres has been regulated by the national codes in Germany in 1992 [7], Italy in 2006 [8] and Spain in 2008 [9], for instance. More recently, recommendations about the design of FRC structures were also included in the MC 2010 [10], with constitutive equations [11][12] and models for the Service Limit State and Ultimate Limit State (SLS and the ULS, respectively). An increase in the use of FRC in tunnels segments has been observed as a result of that [13]. In this regard, it is necessary to update the philosophy applied to the design of tunnel segments in compliance with the particular requirements proposed in the MC 2010, evaluating its applicability and repercussions.The objective of this paper is to present a critical analysis of the design of FRC segments according to the ductility requirements from the MC 2010 and to propose an alternative approach more compatible with the conditions found in practice. First, the design procedure from the MC 2010 is analysed and adapted to FRC segmented linings. Then, the alternative approach is presented. The applicability and repercussion of both approaches in terms of fibre ...

Structural Model for Fibre-Reinforced Precast Concrete Sandwich Panels

“…A usually accepted design criterion requires, to avoid brittle failure under bending, that the ultimate bending capacity (M U ) be larger than the exural cracking moment (M cr ) [30,31]. It can be seen that this criterion is approximately met for the three types of reinforcement, with a small drop for large curvatures in the case of steel bres.…”

Design procedure for precast fibre‐reinforced concrete segments in tunnel lining construction

“…Furthermore, [15] section 7.7.2, introduces some other limitations in terms of displacements which are meant for statically indeterminate structures but do not apply to the analysed case [10].…”

“…For this reason, the check for this phase has to be performed with numerical models and/or full-scale experimental tests in order to simulate, as closely as possible, the actual actions on the segment and to point out the concrete cracking phenomena and predict the crack opening. This aspect is very important because in this kind of structure the crack opening limit has to be complied with [10,[24][25]. aim is to show the practical procedure for defining the M-N envelopes for the phases cited above.…”

“…Recently, the interest in using FRC for the production of precast segments in tunnel linings placed with tunnel boring machines (TBMs) has been growing steadily [5][6][7][8][9][10][11].…”

Monotonic and cyclic behaviour of lightweight concrete beams with and without steel fiber reinforcement

“…In some applications, such as precast tunnel segments, the possibility of totally or partially replace the traditional reinforcement with FRC allows several advantages not only in terms of cost reduction but also related to an increase of the quality and structural performance [32,26,9,15,10,29].…”