PSI - Issue 64

Mehdi Aghabagloo et al. / Procedia Structural Integrity 64 (2024) 1516–1523 Mehdi Aghabagloo/ Structural Integrity Procedia 00 (2019) 000 – 000

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2.2. Experimental results Values of the maximum load, P max , recorded in the single shear tests are provided in Table 1, along with failure modes (shown in Fig. 2). Besides, experimental load-slip curves are presented in Fig. 3.

Table 1: Test results.

Specimen ID

P max (kN)

Failure mode

EBR

29.23 83.69 64.37

C C

HB

HB post-failure * C = cohesive failure in the concrete. * No additional failure mode can be defined. Friction was the failure mechanism acting during this post-failure test.

2.2.1. Failure modes Images of failure modes are shown in Fig. 2. In the EBR specimen, cohesive failure within the concrete was observed (Fig. 2a), indicating that the concrete was the weaker component in the FRP/epoxy/adhesive joint, with cracks propagating until complete debonding occurred. For the case of the HB specimen, cohesive failure within the concrete was also observed at the end of the first test (until complete adhesive bond failure). Final failure mode shown in Fig. 2b corresponds to the end of the second test (conducted to obtain the load-slip curve of the specimen under the compressive stress exerted by the metal plate and referred to as HB post-failure). Unlike the EBR test, where the debonded surface appeared rougher, the HB test showed a smoother debonded surface within the concrete, likely due to friction during the (second) test. This difference may be attributed to the compressive stress applied by the metal anchor. These observations suggest that the concrete was the weaker component in the FRP/epoxy/adhesive joint, consistent with the findings from the EBR test.

Fig. 2 Failure modes of: (a) EBR specimen and (b) HB post-failure specimen.

2.2.2. Load-slip behaviour Experimental load-slip curves are depicted in Fig. 3, grouped by the strengthening technique. In the case of the EBR specimen, an ascending branch is evident until reaching P max =29.23 kN, after which debonding initiates, followed by a horizontal segment until slip reaches a maximum value of 0.50 mm. The presence of a plateau region confirms the achievement of the effective bonded length. The plots corresponding to the two tests performed on the HB specimen are shown in Fig. 3. Red solid line corresponds to the load-slip curve of the first test, where the specimen is tested until the adhesive bond fails entirely. In this case, the load increases until reaching P max =83.69 kN. Following this, debonding occurs, leading to a stabilization phase where the load remains constant. During this phase, the bonded joint is fully damaged and relies solely on friction. The HB-CFRP strengthening technique delays debonding and enhances the load-carrying capacity