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New procedures to design cast-in-situ steel fiber reinforced concrete (SFRC) tunnel linings are briefly presented in this paper. The ductile behavior at ultimate limit stage of such cement-based structures is ensured by a suitable amount of steel fibers and ordinary steel bars. The capability of SFRC to carry tensile stresses, also in the case of wide cracks, allows designers to reduce the minimum area of ordinary steel reinforcement, generally computed in compliance with American or European code requirements. In the serviceability stage, to evaluate crack widths more accurately, a suitable block model is introduced. This model is able to take into account the bridging effect of fibers, as well as the bond slip phenomenon between steel bars and SFRC in tension. Through the combinations of steel fibers and traditional reinforcing bars, it is possible to reduce the global amount of reinforcement in the structure, and contemporarily to increase the speed of construction. Consequently, the global cost of tunneling is reduced as well, particularly in massive structures. The proposed approach has been successfully applied to the design of two different tunnel linings in Italy.

Tailor Made Concrete Structures – Walraven & Stoelhorst (eds) 2008 Taylor & Francis Group, London, ISBN 978-0-415-47535-8
Politecnico di Torino, Italy
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