PSI - Issue 78

Teklewoin Haile Fitwi et al. / Procedia Structural Integrity 78 (2026) 1775–1782

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Furthermore, Specimen 3, intended for basalt FRCM strengthening, demonstrated higher initial performance characteristics with maximum forces of +27.50 kN and -28.07 kN at ±35 mm displacement, representing 24% and 26% higher lateral load capacity compared to Specimen 2. This enhanced performance was attributed to the higher compressive strength of the concrete mixture in Specimen 3 with respect to Specimen 2 (35.40 MPa versus 18.62 MPa). The specimens stiffness degradation pattern was more gradual and stable compared to Specimen 2. Energy dissipation characteristics were moderately improved compared to Specimen 2, though still exhibiting a pinching behavior. 4.3 FRCM strengthened specimens Both carbon and basalt FRCM strengthened specimens demonstrated significant enhancement compared to the unstrengthened baseline as illustrated in Fig. 5. The carbon FRCM strengthened specimen (Specimen 2F) achieved maximum lateral forces of +44.61 kN and -39.96 kN, showing an increase of 51% and 58% respectively compared to the unstrengthened baseline. The basalt FRCM strengthened specimen (Specimen 3F) recorded peak lateral forces of +48.52 kN and -45.88 kN, showing again an increase of 64% and 81% over the unstrengthened specimen. The strength improvements were attributed to the effective contribution of both FRCM systems in enhancing the joint shear capacity by providing efficient external reinforcement to the joint and thereby modifying the failure mechanism from brittle joint shear to more favorable beam-joint mode. The observed strength enhancement was also influenced by the inherent material property variations between specimens as discussed in the following section 4.4. The stiffness degradation patterns (Fig. 5c) were characterized by a more gradual degradation and maintained greater residual stiffness at large displacement amplitudes, indicating an effective composite action between the FRCM systems and concrete substrate. Further, energy dissipation capacity showed also a significant improvement for both strengthening systems over the unstrengthened control specimen (Fig. 4d).

Fig. 5. (a) hysteretic response; (b) envelop ; (c) stiffness degradation; (d) cumulative energy dissipation.