PSI - Issue 64

Andrea Armonico et al. / Procedia Structural Integrity 64 (2024) 604–611 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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3. Results The experimental campaign proposed in this section consists in a medium-large scale strengthened specimen is evaluated when subjected to static and fatigue loading. Each test group provides two beams, one of them is used as a reference without any externally bonded strengthening system; the other one has a 2-layer CFRP externally bonded fabric that is bonded along the total span of the beam to improve its flexional capacity. To assign a nomenclature to the specimens, , the letter T- is assigned to represent the T-shape; in the same way, the suffixes -NR and -R are used to indicate the reference and strengthened beam, respectively. Finally, to identify the beams tested under cyclic loads, the letter -F is added at the end, whereas in the case of a monotonic test, the suffix -M will be used. The tests are performed in 4-point bending. The experimental set aims to evaluate the influence of a CFRP strengthening system As already noted in the first part of the experimental campaign, implementing a composite reinforcement system positively affects the load-bearing capacity of a reinforced concrete element (Rabinovitch and Frostig, 2003; Saadatmanesh and Ehsani, 1991). In detail, the improvement is more significant when the initial element capacity is reduced (Zhang et al., 2021). The following results discussion is focused on the strength improvement of T-shaped beams under 4-point bending. In monotonic tests, the experimental results show an improvement in ultimate load by almost 20%, as illustrated in Figure 3. The failure mode obtained for the strengthened tested beam reflects the optimal situation for structural reinforcement. In fact, the specimen failed due to a tensile failure of the composite in the central area of the beam, allowing to obtain the total strength capacity of the FRP material. The load-displacement curve highlight that the influence of the strengthening system. The FRP efficiency is more evident when steel rebar yields. Indeed, Figure 3 shows the change in slope of the load- displacement curves at the reference’s yielding load, from which the influence of the CFRP fabrics is evident. on several mechanical parameters in an RC beam. 3.1 Strength Improvement and mid span displacement

Figure 3 Comparison in deformability between the reference and strengthened beam Understanding the deformability of the element has a dual function in performance evaluation and monitoring. More significant displacement can affect the structure's functionality under service loads and cause mechanical problems (i.e., cracking) or utilisation problems.