PSI - Issue 84

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

1225

Average compressive strength (MPa)

60.79

Average indirect tensile strength (MPa)

4.26

Fig. 2 illustrates the geometric details of the segment IV and VII, providing the full-scale geometry of the precast tunnel segment IV and VII.

Fig. 2 Geometric characteristics of the precast tunnel segment: (A) Segment VII; (B) Segment IV.

3. Experimental Methodology The four-point bending test was performed at the Laboratory of Earthquake Engineering and Dynamic Analysis (LEDA), Research Centre of the “Kore” University of Enna, Fossetti et al. (2017) , using the EMMA- Experimental high-capacity Modular MAchine . The EMMA machine is particularly innovative because it represents a modular structure with high load-bearing capacity that can take on a variety of load configurations by appropriately moving the modular elements that make up the reaction frame, designed specifically to allow installation in different positions to the base plate ( Strong-Floor ) of the reaction system of LEDA Structures Laboratory. The machine offers singular characteristics on the international scene, both in terms of its load capacity and its modularity, enabling static testing of full-scale structures and infrastructure components. One of the most interesting applications today is precisely the possibility of performing bending and compression tests on prefabricated segments for tunnel lining installed with the TBM. For the purpose of the test hereby presented, the precast tunnel segment specimen was placed on the cylindrical supports by an overhead crane and steel frames specifically designed for the correct distribution of the load were accurately positioned, as shown in Fig. 3. Transducers were mounted at specific positions to measure the structural response. Eight sub-horizontal transducers were placed under the loading points, with four on the right and four on the left side of the specimen, and their main function was to measure crack opening widths. Vertical displacements were monitored with seven vertical transducers that were mounted on the intrados surface. Furthermore, two horizontal transducers were fixed on the supports in order to record any support movements, while one vertical transducer was located on the free edge of the specimen to measure its vertical displacement. This instrumentation setup allowed for the measurement of crack development, displacement, and load transfer mechanisms with high precision during testing.