PSI - Issue 84

Mohammad Javad Azari Nezhadian et al. / Procedia Structural Integrity 84 (2026) 1222–1230

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Load application and the creation of four-point bending conditions were realized by distributing the load linearly and uniformly through two steel beams spanning the specimen. Another steel beam, located above them, ensured that the load coming from the hydraulic jack was uniformly and symmetrically transmitted to the specimen. First, a preload of 300 kN was applied, and subsequently, increased load was applied until the beginning of cracking and the point when the condition of the specimen could be recorded. The load was further increased after the yield of reinforcement and the specimen was loaded until failure. In this paper, the specimens made of RC-SFRC were tested under a four point bending configuration, with transducers directly placed under the loading points and the load uniformly applied in a linear way. Such methodological differences underpin the specific contribution of this study to the assessment of flexural behavior related to RC-SFRC tunnel segments.

Fig. 3 Four-point bending test configuration: (A) Overall view of the testing machine and positioning of the precast tunnel segment; (B) Details of the testing system components; (C) Arrangement of measuring devices. 4. Experimental Results Fig. 4 and Fig. 5 Force-displacement and force- crack mouth opening displacement (CMOD) curves. The two tested segments featured a very similar global flexural behavior under four-point bending. For each specimen, an initial linear regime was clearly visible in which the same stiffness was maintained and no signs of cracking were recorded. The first nonlinear deviations from this linear regime marked the formation of the first flexural cracks at the intrados, within the constant-moment region. Cracking became visible with a steady loss of stiffness, identifying the post cracking phase. Similar overall trajectories were observed for both specimens, but some discrepancies in peak load and residual stiffness appeared.