Title:
Early Age Fracture Behaviour of Self Compacting SFRC for Tunnel Retrofitting: Material Characterization and Structural Transient Design Verification
Author(s):
Liberato Ferrara
Publication:
Web Session
Volume:
ws_S25_EarlyAge_LiberatoFerrara.pdf
Issue:
Appears on pages(s):
Keywords:
DOI:
Date:
3/30/2025
Abstract:
The automation of construction implies that concrete will be subjected since very early ages to combination of actions which may be close to the persistent design situations. In the case of concrete, the determination of mechanical properties and design parameters in early ages may henceforth be crucial with respect to both, the design of the automated construction process and to check the strength and stability at various stages. Vertical and horizontal slip-forming are a remarkable and nowadays quite common examples of a situation in which concrete at a mere few hours of life is called to withstand the self-weight of the just built structural parts and of those progressively interacting with it. In this paper the case study is presented of a new slip-forming technique for tunnel retrofitting and/or new construction, in which, due to the scheduled productivity of the system, Fibre Reinforced Concrete (FRC) tunnel linings of a mere few hours age has to start withstanding their self-weight as well as interacting with the existing lining. A tailored material characterization has been undertaken for the purposely designed extrudable FRC, whose design parameters, as per fib Model Code 2010, have been identified at 4 hours, 8 hours, 24 hours, 72 hours and 7 days, together with more “customary” 28 day deadline. A “stabilization” of the toughness properties of the material has been observed after 24 hours, together with a remarkable deflection hardening. The design parameters identified as above has been henceforth employed to construct design Moment-Axial force interaction domains and moment-curvature sectional diagrams. These have allowed to design the transient design stages of tunnel linings of varying thickness and identify the progressively evolving level of safety for transient design situations in which the same lining has to withstand its self-weight and start interacting with existing lining to allow the construction to proceed as scheduled.